@article {1660,
	title = {Ambient Ammonia Electrosynthesis from Nitrogen and Water by Incorporating Palladium in Bimetallic Gold{\textendash}Silver Nanocages},
	journal = {Journal of The Electrochemical Society},
	year = {2020},
	author = {Nazemi, M. and Soule, L. and Liu, M. and El-Sayed, M. A.}
}
@article {1661,
	title = {Electrosynthesis of Ammonia Using Porous Bimetallic Pd{\textendash}Ag Nanocatalysts in Liquid- and Gas-Phase Systems},
	journal = {ACS Catalysis},
	year = {2020},
	chapter = {10197},
	keywords = {display},
	author = {Nazemi, M. and Ou, P. and Alabbady, A. and Soule, L. and Liu, A. and Song, J. and Sulchek, T.A. and Liu, M. and El-Sayed, M. A.}
}
@article {1653,
	title = {Gold nanomaterials as key suppliers in biological and chemical sensing, catalysis, and medicine},
	journal = {Biochimica et Biophysica Acta (BBA)-General Subjects},
	year = {2020},
	author = {Falahati, M. and Attar, F. and Sharifi, M. and Saboury, A.A. and Salihi, A. and Aziz, F.M. and Kostova, I. and Burda, C. and Priecel, P. and Lopez-Sanchez, J.A. and Laurent, S. and Hooshmand, N. and El-Sayed, M.A.}
}
@article {1658,
	title = {Observation of Photoinduced Proton Transfer between the Titania Surface and Dye Molecule},
	journal = {The Journal of Physical Chemistry C},
	year = {2020},
	author = {Nishikiori, H. and Kondo, H. and Kageshima, Y. and Hooshmand, N. and Panikkanvalappil, S. R. and Valverde-Ch{\'a}vez, D.A. and Silva, C. and El-Sayed, M.A. and Teshima,K.}
}
@article {1659,
	title = {Plasmonic and chiroplasmonic nanobiosensors based on gold nanoparticles},
	journal = {Talanta},
	year = {2020},
	author = {Sharifi, M. and Hosseinali, S.H. and Alizadeh, R.H. and Hasan, A. and Attar, F. and Salihi, A. and Shekha, M.S. and Amen, K.M. and Aziz, F.M. and Saboury, A.A. and Akhtari, K. and Taghizadeh, A. and Hooshmand, N. and El-Sayed, M. A. and Falahati, M.}
}
@article {1662,
	title = {Systems and Methods for Forming Nitrogen-Based Compounds},
	year = {2020},
	author = {Nazemi, M. and El-Sayed, M.A.}
}
@article {1654,
	title = {Collective multipole oscillations direct the plasmonic coupling at the nanojunction interfaces},
	journal = {Proceedings of the National Academy of Sciences},
	year = {2019},
	author = {Hooshmand, N. and El-Sayed, M.A.}
}
@article {1656,
	title = {Enhanced Electrochemical Dark-Field Scattering Modulation on Single Hybrid Core-Shell Nanostructure},
	journal = {The Journal of Physical Chemistry C},
	year = {2019},
	author = {Zhou, J. and Panikkanvalappil, S.R. and Kang, S. and Yu, S. and Zhang, S. and El-Sayed, M.A. and Tsukruk, V.V.}
}
@article {1652,
	title = {Enhancing Plasmonic{\textendash}Photonic Hybrid Cavity Modes by Coupling of Individual Plasmonic Nanoparticles},
	journal = {The Journal of Physical Chemistry C},
	year = {2019},
	author = {Zhang, S. and Panikkanvalappil, S.R. and Kang, S. and Smith, M.J. and Yu, S. and El-Sayed, M. and Tsukruk, V.V.}
}
@article {1647,
	title = {Gold Nanoparticle-Assisted Plasmonic Photothermal Therapy Advances towards Clinical Application},
	journal = {The Journal of Physical Chemistry C},
	year = {2019},
	chapter = {15375},
	author = {Ali, M.R. and Wu, Y. and El-Sayed, M.A.}
}
@article {1644,
	title = {Gold nanoparticles in biological optical imaging},
	journal = {Nano Today},
	year = {2019},
	chapter = {120},
	author = {Wu, Y. and Ali, M.R. and Chen, K. and Fang, N. and El-Sayed, M.A.}
}
@article {1650,
	title = {Gold Nanorod-Assisted Photothermal Therapy Decreases Bleeding during Breast Cancer Surgery in Dogs and Cats},
	journal = {Cancers},
	year = {2019},
	author = {Ali, M.R. and Farghali, H.A. and Wu, Y. and El-Sayed, I. and Osman, A.H. and Selim, S.A. and El-Sayed, M.A.}
}
@article {1655,
	title = {Improving the Flow Cytometry-based Detection of the Cellular Uptake of Gold Nanoparticles},
	journal = {Analytical chemistry},
	year = {2019},
	author = {Wu, Y. and Ali, M.R. and Dansby, K. and El-Sayed, M.A.}
}
@article {1645,
	title = {Methods for inhibiting cancer cell migration with gold nanomaterials and photothermal therapy},
	year = {2019},
	author = {El-Sayed, M.A. and Ali, M.R.}
}
@article {1643,
	title = {Monitoring the dynamics of hemeoxygenase-1 activation in head and neck cancer cells in real-time using plasmonically enhanced Raman spectroscopy},
	journal = {Chemical Science},
	year = {2019},
	author = {Panikkanvalappil, S. R. and Garlapati, C. and Hooshmand, N. and Aneja, R. and El-Sayed, M. A.}
}
@article {1649,
	title = {Operando Investigation into Dynamic Evolution of Cathode{\textendash}Electrolyte Interfaces in a Li-Ion Battery},
	journal = {Nano letters},
	year = {2019},
	author = {Chen, D. and Mahmoud, M.A. and Wang, J.H. and Waller, G.H. and Zhao, B. and Qu, C. and El-Sayed, M.A. and Liu, M.}
}
@article {1648,
	title = {Plasmon-enhanced photo (electro) chemical nitrogen fixation under ambient conditions using visible light responsive hybrid hollow Au-Ag2O nanocages},
	journal = {Nano Energy},
	year = {2019},
	author = {Nazemi, M. and El-Sayed, M.A.}
}
@article {1651,
	title = {Plasmonic gold nanoparticles: Optical manipulation, imaging, drug delivery and therapy},
	journal = {Journal of Controlled Release},
	year = {2019},
	author = {Sharifi, M. and Attar, F. and Saboury, A.A. and Akhtari, K. and Hooshmand, N. and Hasan, A. and El-Sayed, M.A. and Falahati, M.}
}
@article {1646,
	title = {The Role of Oxidation of Silver in Bimetallic Gold{\textendash}Silver Nanocages on Electrocatalytic Activity of Nitrogen Reduction Reaction},
	journal = {The Journal of Physical Chemistry C},
	year = {2019},
	chapter = {11422},
	author = {Nazemi, M. and El-Sayed, M.A.}
}
@article {1632,
	title = {Defect engineering in 1D Ti{\textendash}W oxide nanotube arrays and their correlated photoelectrochemical performance},
	journal = {Physical Chemistry Chemical Physics},
	year = {2018},
	chapter = {10258},
	author = {A.A. Abdelhafiz and M.A. Ganzoury and Amer, A. W. and A.A. Faiad and A.M. Khalifa and S.Y. AlQaradawi and El-Sayed, M. A. and Alamgir, F. M. and Allam, N. K.}
}
@article {1636,
	title = {Dual-excitation nanocellulose-plasmonic membranes for molecular and cellular SERS detection},
	journal = {ACS applied materials \& interfaces},
	year = {2018},
	author = {S. Zhang and R. Xiong and Mahmoud, M A and E. Quigley and H. Chang and El-Sayed, M. A. and Tsukruk, V. V.}
}
@article {1640,
	title = {Electrochemical Synthesis of Ammonia from N2 and H2O under Ambient Conditions Using Pore-Size-Controlled Hollow Gold Nanocatalysts with Tunable Plasmonic Properties},
	journal = {The journal of physical chemistry letters},
	year = {2018},
	author = {M. Nazemi and El-Sayed, M. A.}
}
@article {1637,
	title = {Enhancing the rate of electrochemical nitrogen reduction reaction for ammonia synthesis under ambient conditions using hollow gold nanocages},
	journal = {Nano Energy},
	year = {2018},
	keywords = {display},
	author = {M. Nazemi and Panikkanvalappil, S. R. and El-Sayed, M. A.}
}
@inbook {1633,
	title = {Gold nanoparticles for cancer diagnostics, spectroscopic imaging, drug delivery, and plasmonic photothermal therapy},
	booktitle = {Inorganic Frameworks as Smart Nanomedicines},
	year = {2018},
	chapter = {2},
	author = {M. Aioub and L.A. Austin and El-Sayed, M. A.}
}
@article {1639,
	title = {Gold Nanorod-Photothermal Therapy Alters Cell Junctions and Actin Network in Inhibiting Cancer Cell Collective Migration},
	journal = {ACS nano},
	year = {2018},
	author = {Y. Wu and Ali, M. R. K. and B. Dong and T. Han and K. Chen and J. Chen and Y. Tang and N. Fang and F. Wang and El-Sayed, M. A.}
}
@article {1638,
	title = {Real-Time Tracking of Autophagy Process in Living Cells Using Plasmonically Enhanced Raman Spectroscopy of Fucoidan-Coated Gold Nanoparticles},
	journal = {Journal of Materials Chemistry B},
	year = {2018},
	author = {Jang, H and K. Kang and El-Sayed, M. A.}
}
@article {1634,
	title = {Single-Crystal Electrospun Plasmonic Perovskite Nanofibers},
	journal = {The Journal of Physical Chemistry C},
	year = {2018},
	author = {A.M. Abdellah and A. Hafez and Panikkanvalappil, S. R. and El-Sayed, M. A. and Allam, N. K.}
}
@article {1635,
	title = {UV Resonance Raman Study of Apoptosis, Platinum-based Drugs, and Human Cell Lines},
	journal = {ChemPhysChem},
	year = {2018},
	author = {Geng, J and M. Aioub and El-Sayed, M. A. and B.A. Barry}
}
@article {1611,
	title = {A force for Egyptian science},
	journal = {Proceedings of the National Academy of Sciences},
	year = {2017},
	author = {El-Sayed, Mostafa A. and Zewail, Ahmed}
}
@article {1610,
	title = {Shape tunable plasmonic nanoparticles},
	volume = {9,588,124},
	year = {2017},
	author = {El-Sayed, M. A. and El-Sayed, I H}
}
@article {1593,
	title = { Electrically Controlled Plasmonic Behavior of Gold Nanocube@ Polyaniline Nanostructures: Transparent Plasmonic Aggregates},
	journal = {Chem. Mater.},
	year = {2016},
	author = {Jeon, J.-W. and Ledin, P. A. and Geldmeier, J. A. and Ponder, J. F. and Mahmoud, M A and El-Sayed, M. and Reynolds, J. R. and Tsukruk, V. V.}
}
@article {1590,
	title = {Elucidation of Ultraviolet RadiationInduced Cell Responses and Intracellular Biomolecular Dynamics in Mammalian Cells Using Surface-Enhanced Raman Spectroscopy},
	journal = {Chemical Science },
	year = {2016},
	author = {Panikkanvalappil, S. R. and Hira, S. M. and El-Sayed, M. A.}
}
@article {1584,
	title = {Hyperoxia Induces Intracellular Acidification in Neonatal Mouse Lung Fibroblasts: Real-Time Investigation Using Plasmonically Enhanced Raman Spectroscopy},
	journal = {Journal of the American Chemical Society},
	volume = {138},
	year = {2016},
	pages = {3779{\textendash}3788},
	author = {Panikkanvalappil, Sajanlal R. and James, Masheika and Hira, Steven M and Mobley, James and Jilling, Tamas and Ambalavanan, Namasivayam and El-Sayed, Mostafa A.}
}
@article {1588,
	title = { Large Enhancement of Circular Dichroism Using an Embossed Chiral Metamaterial},
	journal = { arXiv preprint},
	year = {2016},
	doi = {1604.05244},
	author = {Mousavi, S.; and Panikkanvalappil, S. R.; and El-Sayed, M. A.; and Eftekhar, A. A.; and Adibi, A.}
}
@article {1592,
	title = { Photoexcited Surface Frustrated Lewis Pairs for Heterogeneous Photocatalytic Co2 Reduction},
	journal = { Am. Chem. Soc. },
	year = {2016},
	author = {Ghuman, K. K. and Hoch, L. B. and Szymanski, P. and Loh, J. Y. and Kherani, N. P. and El-Sayed, M. A. and Ozin, G. A. and Singh, C. V.}
}
@article {1587,
	title = {Probing Structural Evolution and Charge Storage Mechanism of Nio2hx Electrode Materials Using in Operando Resonance Raman Spectroscopy},
	journal = { Advanced Science},
	year = {2016},
	author = {Chen, D. and Xiong, X. and Zhao, B. and Mahmoud, M A and El-Sayed, M. A. and Liu, M.}
}
@article {1583,
	title = {A Real-Time Surface Enhanced Raman Spectroscopy Study of Plasmonic Photothermal Cell Death Using Targeted Gold Nanoparticles},
	journal = {Journal of the American Chemical Society},
	year = {2016},
	author = {Aioub, Mena S and El-Sayed, Mostafa A.}
}
@article {1585,
	title = {The Sensitivity of the Distance Dependent Plasmonic Coupling between Two Nanocubes to their Orientation: Edge-to-Edge versus Face-to-Face},
	journal = {The Journal of Physical Chemistry C},
	volume = {120},
	year = {2016},
	pages = {4564{\textendash}4570},
	author = {Hooshmand, Nasrin and Bordley, Justin A and El-Sayed, Mostafa A.}
}
@article {1589,
	title = { Tuning the Photoactivity of Zirconia NanotubesBased Photoanodes Via Ultra-Thin Layers of Zrn: An Effective Approach Towards Visible Light-Water Splitting},
	journal = { J. Phys. Chem.},
	year = {2016},
	author = {Amer, A. W. and El-Sayed, M. A. and Allam, N. K.}
}
@article {1620,
	title = {Virtual Issue in Memory of Ahmed Zewail},
	journal = {Journal of Physical Chemistry B},
	year = {2016},
	author = {El-Sayed, Mostafa A. and Schatz, GC}
}
@article {1572,
	title = {The Coupling between Gold or Silver Nanocubes in Their Homo-Dimers: A New Coupling Mechanism at Short Separation Distances},
	journal = {Nano Letters},
	volume = {15},
	year = {2015},
	pages = {3391-3397},
	doi = {10.1021/acs.nanolett.5b00734},
	url = {http://dx.doi.org/10.1021/acs.nanolett.5b00734},
	author = {Bordley, Justin A and Hooshmand, Nasrin and El-Sayed, Mostafa A.}
}
@article {1582,
	title = {Cytotoxic effects of cytoplasmic-targeted and nuclear-targeted gold and silver nanoparticles in HSC-3 cells{\textendash}A mechanistic study},
	journal = {Toxicology in Vitro},
	volume = {29},
	year = {2015},
	pages = {694{\textendash}705},
	author = {Lauren A. Austin and Ahmad, Samera and Kang, Bin and Rommel, Kathryn R and Mahmoud, Mahmoud and Peek, Mary E and El-Sayed, Mostafa A.}
}
@article {1573,
	title = {Electronic and Vibrational Dynamics of Hollow Au Nanocages Embedded in Cu2O Shells},
	journal = {Photochemistry and Photobiology},
	volume = {91},
	year = {2015},
	pages = {599{\textendash}606},
	issn = {1751-1097},
	doi = {10.1111/php.12432},
	url = {http://dx.doi.org/10.1111/php.12432},
	author = {Szymanski, Paul and Mahmoud, Mahmoud A. and O{\textquoteright}Neil, Daniel and Garlyyev, Batyr and El-Sayed, Mostafa A.}
}
@article {1575,
	title = {Light-responsive plasmonic arrays consisting of silver nanocubes and a photoisomerizable matrix.},
	journal = {ACS Appl Mater Interfaces},
	volume = {7},
	year = {2015},
	month = {2015 Mar 4},
	pages = {4902-12},
	abstract = {We report on the synthesis of novel branched organic-inorganic azo-polyhedral oligomeric silsesquioxane (POSS) conjugates (Azo-POSS) and their use as a stable active medium to induce reversible plasmonic modulations of embedded metal nanostructures. A dense monolayer of silver nanocubes was deposited on a quartz substrate using the Langmuir-Blodgett technique and subsequently coated with an ultrathin Azo-POSS layer. The reversible light-induced photoisomerization between the trans and cis states of the azobenzene-terminated branched POSS material results in significant changes in the refractive index (up to 0.17) at a wavelength of 380 nm. We observed that the pronounced and reversible change in the surrounding refractive index results in a corresponding hypsochromic plasmonic shift of 6 nm in the plasmonic band of the embedded silver nanocubes. The reversible tuning of the plasmonic modes of noble-metal nanostructures using a variable-refractive-index medium opens up the possibility of fabricating photoactive, hybrid, ultrathin coatings with robust, real-time, photoinitiated responses for prospective applications in photoactive materials that can be reversibly tuned by light illumination.},
	issn = {1944-8252},
	doi = {10.1021/am508993z},
	author = {Ledin, Petr A and Russell, Michael and Geldmeier, Jeffrey A and Tkachenko, Ihor M and Mahmoud, Mahmoud A. and Shevchenko, Valery and El-Sayed, Mostafa A. and Tsukruk, Vladimir V.}
}
@article {1574,
	title = {Near-Infrared Asymmetrical Squaraine Sensitizers for Highly Efficient Dye Sensitized Solar Cells: The Effect of π-Bridges and Anchoring Groups on Solar Cell Performance},
	journal = {Chemistry of Materials},
	volume = {27},
	year = {2015},
	pages = {2480-2487},
	doi = {10.1021/cm5045946},
	url = {http://dx.doi.org/10.1021/cm5045946},
	author = {Fadi M. Jradi and Xiongwu Kang and O{\textquoteright}Neil, Daniel and Gabriel Pajares and Yulia A. Getmanenko and Szymanski, Paul and Timothy C. Parker and El-Sayed, Mostafa A. and Seth R. Marder}
}
@article {1577,
	title = {Plasmonic Spectroscopy: The Electromagnetic Field Strength and its Distribution Determine the Sensitivity Factor of Face-to-Face Ag Nanocube Dimers in Solution and on a Substrate},
	journal = {The Journal of Physical Chemistry C},
	volume = {119},
	year = {2015},
	pages = {15579-15587},
	doi = {10.1021/acs.jpcc.5b05395},
	url = {http://dx.doi.org/10.1021/acs.jpcc.5b05395},
	author = {Hooshmand, Nasrin and Bordley, Justin A and El-Sayed, Mostafa A.}
}
@article {1580,
	title = {Probing molecular cell event dynamics at the single-cell level with targeted plasmonic gold nanoparticles: A review},
	journal = {Nano Today},
	year = {2015},
	pages = {-},
	keywords = {Rayleigh scattering},
	issn = {1748-0132},
	doi = {http://dx.doi.org/10.1016/j.nantod.2015.07.005},
	url = {http://www.sciencedirect.com/science/article/pii/S1748013215000973},
	author = {Lauren A. Austin and Bing Kang and El-Sayed, Mostafa A.}
}
@article {1576,
	title = {Silver nanocube aggregation gradient materials in search for total internal reflection with high phase sensitivity},
	journal = {Nanoscale},
	volume = {7},
	year = {2015},
	pages = {5230-5239},
	abstract = {We fabricated monolayer coatings of a silver nanocube aggregation to create a step-wise optical strip by applying different surface pressures during slow Langmuir-Blodgett deposition. The varying amount of randomly distributed nanocube aggregates with different surface coverages in gradient manner due to changes in surface pressure allows for continuous control of the polarization sensitive absorption of the incoming light over a broad optical spectrum. Optical characterization under total internal reflection conditions combined with electromagnetic simulations reveal that the broadband light absorption depends on the relative orientation of the nanoparticles to the polarization of the incoming light. By using computer simulations, we found that the electric field vector of the s-polarized light interacts with the different types of silver nanocube aggregations to excite different plasmonic resonances. The s-polarization shows dramatic changes of the plasmonic resonances at different angles of incidence (shift of 64 nm per 10[degree] angle of incidence). With a low surface nanocube coverage (from 5\% to 20\%), we observed a polarization-selective high absorption of 80\% (with an average 75\%) of the incoming light over a broad optical range in the visible region from 400 nm to 700 nm. This large-area gradient material with location-dependent optical properties can be of particular interest for broadband light absorption, phase-sensitive sensors, and imaging.},
	doi = {10.1039/C4NR06430E},
	url = {http://dx.doi.org/10.1039/C4NR06430E},
	author = {Konig, Tobias A. F. and Ledin, Petr A and Russell, Michael and Geldmeier, Jeffrey A and Mahmoud, Mahmoud. A. and El-Sayed, Mostafa A. and Tsukruk, Vladimir V.}
}
@article {1578,
	title = {Wavelength-Selective Photocatalysis Using Gold{\textendash}Platinum Nanorattles},
	journal = {The Journal of Physical Chemistry C},
	volume = {119},
	year = {2015},
	pages = {18618-18626},
	doi = {10.1021/acs.jpcc.5b05967},
	url = {http://dx.doi.org/10.1021/acs.jpcc.5b05967},
	author = {Mahmoud, Mahmoud A. and Garlyyev, Batyr and El-Sayed, Mostafa A.}
}
@article {1367,
	title = {Are hot spots between two plasmonic nanocubes of silver or gold formed between adjacent corners or adjacent facets? A DDA examination},
	journal = {The Journal of Physical Chemistry Letters},
	year = {2014},
	isbn = {1948-7185},
	author = {Hooshmand, Nasrin and El-Sayed, Mostafa A. and Bordley, Justin A}
}
@article {1360,
	title = {Chemosensitization of Cancer Cells via Gold Nanoparticle-Induced Cell Cycle Regulation},
	journal = {Photochemistry and photobiology},
	volume = {90},
	number = {2},
	year = {2014},
	pages = {306-312},
	isbn = {1751-1097},
	author = {Mackey, Megan A. and El-Sayed, Mostafa A}
}
@article {1363,
	title = {Electrically Tunable Plasmonic Behavior of Nanocube-Polymer Nanomaterials Induced by a Redox Active Electrochromic Polymer},
	journal = {ACS nano},
	year = {2014},
	isbn = {1936-0851},
	author = {K{\"o}nig, Tobias AF and Ledin, Petr A and Kerszulis, Justin and Mahmoud, Mahmoud A. and El-Sayed, Mostafa A. and Reynolds, John R and Tsukruk, Vladimir V.}
}
@article {1371,
	title = {Energy-Transfer Efficiency in Eu-Doped ZnO Thin Films: The Effects of Oxidative Annealing on the Dynamics and the Intermediate Defect States},
	journal = {Acs Applied Materials \& Interfaces},
	volume = {6},
	number = {3},
	year = {2014},
	note = {Ahmed, Samah M. Szymanski, Paul El-Nadi, Lotfia M. El-Sayed, Mostafa A.},
	month = {Feb},
	pages = {1765-1772},
	isbn = {1944-8244},
	doi = {10.1021/am404662k},
	author = {Ahmed, S. M. and Szymanski, P. and El-Nadi, L. M. and El-Sayed, M. A.}
}
@article {1370,
	title = {Enhancing the Efficiency of Gold Nanoparticles Treatment of Cancer by Increasing Their Rate of Endocytosis and Cell Accumulation Using Rifampicin},
	journal = {Journal of the American Chemical Society},
	volume = {136},
	number = {12},
	year = {2014},
	pages = {4464-4467},
	isbn = {0002-7863},
	author = {Ali, Moustafa RK and Panikkanvalappil, Sajanlal R. and El-Sayed, Mostafa A.}
}
@article {1362,
	title = {High-temperature surface enhanced Raman spectroscopy for in situ study of solid oxide fuel cell materials},
	journal = {Energy \& Environmental Science},
	volume = {7},
	number = {1},
	year = {2014},
	pages = {306-310},
	author = {Li, Xiaxi and Lee, Jung-Pil and Blinn, Kevin S and Chen, Dongchang and Yoo, Seungmin and Kang, Bin and Bottomley, Lawrence A and El-Sayed, Mostafa A. and Park, Soojin and Liu, Meilin}
}
@article {1358,
	title = {Hollow and Solid Metallic Nanoparticles in Sensing and in Nanocatalysis},
	journal = {Chemistry of Materials},
	volume = {26},
	number = {1},
	year = {2014},
	note = {Mahmoud, Mahmoud A. O{\textquoteright}Neil, Daniel El-Sayed, Mostafa A.Si},
	month = {Jan},
	pages = {44-58},
	keywords = {n/a},
	isbn = {0897-4756},
	doi = {10.1021/cm4020892},
	author = {Mahmoud, M A and O{\textquoteright}Neil, D. and El-Sayed, M. A.}
}
@article {1361,
	title = {The Most Effective Gold Nanorod Size for Plasmonic Photothermal Therapy: Theory and In Vitro Experiments},
	journal = {Journal of Physical Chemistry B},
	volume = {118},
	number = {5},
	year = {2014},
	note = {Mackey, Megan A. Ali, Moustafa R. K. Austin, Lauren A. Near, Rachel D. El-Sayed, Mostafa A.},
	month = {Feb},
	pages = {1319-1326},
	isbn = {1520-6106},
	doi = {10.1021/jp409298f},
	author = {Mackey, M. A. and Ali, M. R. K. and Austin, Lauren and Near, R. D. and El-Sayed, M. A.}
}
@article {1365,
	title = {Observing Real-Time Molecular Event Dynamics of Apoptosis in Living Cancer Cells using Nuclear-Targeted Plasmonically Enhanced Raman Nanoprobes},
	journal = {ACS nano},
	volume = {8},
	number = {5},
	year = {2014},
	pages = {4883-4892},
	isbn = {1936-0851},
	author = {Kang, Bin and Austin, Lauren and El-Sayed, Mostafa A.}
}
@article {1369,
	title = {The optical, photothermal, and facile surface chemical properties of gold and silver nanoparticles in biodiagnostics, therapy, and drug delivery},
	journal = {Archives of Toxicology},
	year = {2014},
	pages = {1-27},
	isbn = {0340-5761},
	author = {Austin, Lauren and Mackey, Megan A. and Dreaden, Erik C. and El-Sayed, Mostafa A.}
}
@article {1368,
	title = {P-Glycoprotein-Dependent Trafficking of Nanoparticle-Drug Conjugates},
	journal = {Small},
	volume = {10},
	number = {9},
	year = {2014},
	pages = {1719-1723},
	isbn = {1613-6829},
	author = {Dreaden, Erik C. and Raji, Idris O and Austin, Lauren and Fathi, Shaghayegh and Mwakwari, Sandra C and Humphries, William H and Kang, Bin and Oyelere, Adegboyega K and El-Sayed, Mostafa A}
}
@article {1356,
	title = {Self-Assembled Nanostructured Photoanodes with Staggered Bandgap for Efficient Solar Energy Conversion},
	journal = {ACS nano},
	year = {2014},
	isbn = {1936-0851},
	author = {Nashed, Ramy and Szymanski, Paul and El-Sayed, Mostafa A. and Allam, Nageh K}
}
@article {1359,
	title = {Shape- and Symmetry-Dependent Mechanical Properties of Metallic Gold and Silver on the Nanoscale},
	journal = {Nano Letters},
	volume = {14},
	number = {2},
	year = {2014},
	note = {Mahmoud, Mahmoud A. O{\textquoteright}Neil, Daniel El-Sayed, Mostafa A.},
	month = {Feb},
	pages = {743-748},
	isbn = {1530-6984},
	doi = {10.1021/nl4040362},
	author = {Mahmoud, M A and O{\textquoteright}Neil, D. and El-Sayed, M. A.}
}
@article {1364,
	title = {Silver Nanocube Aggregates in Cylindrical Pores for Higher Refractive Index Plasmonic Sensing},
	journal = {Particle \& Particle Systems Characterization},
	volume = {31},
	number = {2},
	year = {2014},
	pages = {274-283},
	isbn = {1521-4117},
	author = {K{\"o}nig, Tobias and Kodiyath, Rajesh and Combs, Zachary A. and Mahmoud, Mahmoud and El-Sayed, Mostafa A and Tsukruk, Vladimir V.}
}
@article {1366,
	title = {The Spectroscopy of Homo and Heterodimers of Silver and Gold Nanocubes as a Function of Separation: a DDA Simulation},
	journal = {The Journal of Physical Chemistry A},
	year = {2014},
	isbn = {1089-5639},
	author = {Hooshmand, Nasrin and O{\textquoteright}Neil, Daniel and Asiri, Abdullah M and El-Sayed, Mostafa A.}
}
@article {1357,
	title = {Stacked Gold Nanorectangles with Higher Order Plasmonic Modes and Top-Down Plasmonic Coupling},
	journal = {The Journal of Physical Chemistry C},
	volume = {118},
	number = {10},
	year = {2014},
	pages = {5453-5462},
	isbn = {1932-7447},
	author = {Malak, Sidney T. and König, Tobias and Near, Rachel and Combs, Zachary A. and El-Sayed, Mostafa A. and Tsukruk, Vladimir V.}
}
@article {1373,
	title = {XAV939: From a Small Inhibitor to a Potent Drug Bioconjugate When Delivered by Gold Nanoparticles},
	journal = {Bioconjugate Chemistry},
	volume = {25},
	number = {2},
	year = {2014},
	note = {Afifi, Marwa M. Austin, Lauren A. Mackey, Megan A. El-Sayed, Mostafa A.},
	month = {Feb},
	pages = {207-215},
	isbn = {1043-1802},
	doi = {10.1021/bc400271x},
	author = {Afifi, M. M. and Austin, Lauren and Mackey, M. A. and El-Sayed, M. A.}
}
@article {1399,
	title = {Aptamer-Assisted Assembly of Gold Nanoframe Dimers},
	journal = {Particle \& Particle Systems Characterization},
	volume = {30},
	number = {12},
	year = {2013},
	pages = {1071-1078},
	isbn = {1521-4117},
	author = {Combs, Zachary A. and Malak, Sidney T. and K{\"o}nig, Tobias and Mahmoud, Mahmoud A. and Ch{\'a}vez, Jorge L and El-Sayed, Mostafa A and Kelley-Loughnane, Nancy and Tsukruk, Vladimir V.}
}
@article {1349,
	title = {Assemblies of silver nanocubes for highly sensitive SERS chemical vapor detection},
	journal = {J. Mater. Chem. A},
	volume = {1},
	number = {8},
	year = {2013},
	note = {CAPLUS AN 2013:172950(Journal; Online Computer File)},
	month = {//},
	pages = {2777-2788},
	publisher = {Royal Society of Chemistry},
	type = {10.1039/c2ta00867j},
	abstract = {Probably Ag nanocube (AgNC) aggregates within cylindrical pores (PAM-AgNC) can be employed as efficient nanostructures for highly efficient, robust, tunable, and reusable surface-enhanced Raman scattering (SERS) substrates for trace level org. vapor detection which is a challenging task in chem. detection. The authors demonstrate the ability to tune both the detection limit and the onset of signal satn. of the substrate by switching the adsorption behavior of AgNCs between highly aggregated and more disperse by varying the no. of adsorption-mediating polyelectrolyte bilayers on the pore walls of the membrane. The different AgNC distributions show large differences in the trace vapor detection limit of the common Raman marker benzenethiol (BT) and a widely used explosive binder N-Me-4-nitroaniline (MNA), demonstrating the importance of the large electromagnetic field enhancement assocd. with AgNC coupling. The SERS substrate with highly aggregated AgNCs within the cylindrical pores allows for consistent trace detection of mid ppb (\~{}500) for BT analyte, and a record limit of detection of low ppb (\~{}3) for MNA vapors with an estd. achievable limit of detection of \~{}600 ppt. The dispersed AgNC aggregates do not sat. at higher ppb concns., providing an avenue to distinguish between higher ppb concns. and increase the effective range of the SERS substrate design. A comparison between the AgNC substrate and an electroless deposition substrate with Ag quasi-nanospheres (PAM-AgNS) also demonstrates a higher SERS activity, and better detection limit, by the nanocube aggregates. This is supported by FDTD electromagnetic simulations that suggest that the higher integrated electromagnetic field intensity of the hot spots and the large specific interfacial areas impart greatly improved SERS for the AgNCs. Also, the AgNC substrate can be reused multiple times without significant loss of SERS activity which opens up new avenues for in-field monitoring. [on SciFinder(R)]},
	keywords = {polymer electrolyte film silver nanocube nanosphere SERS sensor explosive, porous alumina silver nanoparticle SERS substrate explosive, silver nanocube nanosphere SERS sensor benzenethiol methyl nitroaniline polyelectrolyte, vapor sensor silver nanoparticle SERS substrate},
	isbn = {2050-7496},
	doi = {10.1039/c2ta00867j},
	author = {Kodiyath, Rajesh and Malak, Sidney T. and Combs, Zachary A. and Koenig, Tobias and Mahmoud, Mahmoud A. and El-Sayed, Mostafa A. and Tsukruk, Vladimir V.}
}
@article {1384,
	title = {Bandgap bowing in Ta-W-O system for efficient solar energy conversion: Insights from density functional theory and X-ray diffraction},
	journal = {Applied Physics Letters},
	volume = {103},
	number = {13},
	year = {2013},
	note = {Nashed, Ramy Alamgir, Faisal M. Jang, Seung Soon Ismail, Yehea El-Sayed, Mostafa A. Allam, Nageh K.},
	month = {Sep},
	isbn = {0003-6951},
	doi = {10.1063/1.4823543},
	author = {Nashed, R. and Alamgir, F. M. and Jang, S. S. and Ismail, Y. and El-Sayed, M. A. and Allam, N. K.}
}
@article {1388,
	title = {Determining the Mechanism of Solution Metallic Nanocatalysis with Solid and Hollow Nanoparticles: Homogeneous or Heterogeneous},
	journal = {Journal of Physical Chemistry C},
	volume = {117},
	number = {42},
	year = {2013},
	note = {Mahmoud, Mahmoud A. Garlyyev, Batyr El-Sayed, Mostafa A.},
	month = {Oct},
	pages = {21886-21893},
	isbn = {1932-7447},
	doi = {10.1021/jp4079234},
	author = {Mahmoud, M A and Garlyyev, B. and El-Sayed, M. A.}
}
@article {1391,
	title = {Different Plasmon Sensing Behavior of Silver and Gold Nanorods},
	journal = {Journal of Physical Chemistry Letters},
	volume = {4},
	number = {9},
	year = {2013},
	note = {Mahmoud, Mahmoud A. El-Sayed, Mostafa A.},
	month = {May},
	pages = {1541-1545},
	isbn = {1948-7185},
	doi = {10.1021/jz4005015},
	author = {Mahmoud, M A and El-Sayed, M. A.}
}
@article {1376,
	title = {Electron transfer process in fluorescein-dispersing titania gel films observed by time-resolved fluorescence spectroscopy},
	journal = {The Journal of Physical Chemistry C},
	volume = {117},
	number = {20},
	year = {2013},
	pages = {10308-10314},
	isbn = {1932-7447},
	author = {Setiawan, Rudi Agus and Nishikiori, Hiromasa and Uesugi, Yohei and Miyashita, Kyohei and El-Sayed, Mostafa A. and Fujii, Tsuneo}
}
@article {1350,
	title = {Enhancing Colloidal Metallic Nanocatalysis: Sharp Edges and Corners for Solid Nanoparticles and Cage Effect for Hollow Ones},
	journal = {Acc Chem Res},
	year = {2013},
	note = {MEDLINE AN 2013361444(Journal; Article; (JOURNAL ARTICLE))},
	month = {//},
	abstract = {There are two main classes of metallic nanoparticles: solid and hollow. Each type can be synthesized in different shapes and structures. Practical use of these nanoparticles depends on the properties they acquire on the nanoscale. Plasmonic nanoparticles of silver and gold are the most studied, with applications in the fields of sensing, medicine, photonics, and catalysis. In this Account, we review our group{\textquoteright}s work to understand the catalytic properties of metallic nanoparticles of different shapes. Our group was the first to synthesize colloidal metallic nanoparticles of different shapes and compare their catalytic activity in solution. We found that the most active among these were metallic nanoparticles having sharp edges, sharp corners, or rough surfaces. Thus, tetrahedral platinum nanoparticles are more active than spheres. We proposed this happens because sharper, rougher particles have more valency-unsatisfied surface atoms (i.e., atoms that do not have the complete number of bonds that they can chemically accommodate) to act as active sites than smoother nanoparticles. We have not yet resolved whether these catalytically active atoms act as catalytic centers on the surface of the nanoparticle (i.e., heterogeneous catalysis) or are dissolved by the solvent and perform the catalysis in solution (i.e., homogenous catalysis). The answer is probably that it depends on the system studied. In the past few years, the galvanic replacement technique has allowed synthesis of hollow metallic nanoparticles, often called nanocages, including some with nested shells. Nanocage catalysts show strong catalytic activity. We describe several catalytic experiments that suggest the reactions occurred within the cage of the hollow nanocatalysts: (1) We synthesized two types of hollow nanocages with double shells, one with platinum around palladium and the other with palladium around platinum, and two single-shelled nanocages, one made of pure platinum and the other made of pure palladium. The kinetic parameters of each double-shelled catalyst were comparable to those of the single-shelled nanocage of the same metal as the inside shell, which suggests the reactions are taking place inside the cavity. (2) In the second set of experiments, we used double-shelled, hollow nanoparticles with a plasmonic outer gold surface and a non-plasmonic inner catalytic layer of platinum as catalysts. As the reaction proceeded and the dielectric function of the interior gold cavity changed, the plasmonic band of the interior gold shell shifted. This strongly suggested that the reaction had taken place in the nanocage. (3) Finally, we placed a catalyst on the inside walls of hollow nanocages and monitored the corresponding reaction over time. The reaction rate depended on the size and number of holes in the walls of the nanoparticles, strongly suggesting the confinement effect of a nanoreactor.[on SciFinder (R)]},
	isbn = {1520-4898},
	author = {Mahmoud, Mahmoud A. and Narayanan, Radha and El-Sayed, Mostafa A.}
}
@article {1395,
	title = {Exploiting the Nanoparticle Plasmon Effect: Observing Drug Delivery Dynamics in Single Cells via Raman/Fluorescence Imaging Spectroscopy},
	journal = {Acs Nano},
	volume = {7},
	number = {8},
	year = {2013},
	note = {Kang, Bin Afifi, Marwa M. Austin, Lauren A. El-Sayed, Mostafa A.},
	month = {Aug},
	pages = {7420-7427},
	isbn = {1936-0851},
	doi = {10.1021/nn403351z},
	author = {Kang, B. and Afifi, M. M. and Austin, Lauren and El-Sayed, M. A.}
}
@article {1389,
	title = {High-Frequency Mechanical Stirring Initiates Anisotropic Growth of Seeds Requisite for Synthesis of Asymmetric Metallic Nanoparticles like Silver Nanorods},
	journal = {Nano Letters},
	volume = {13},
	number = {10},
	year = {2013},
	note = {Mahmoud, Mahmoud A. El-Sayed, Mostafa A. Gao, Jianping Landman, Uzi},
	month = {Oct},
	pages = {4739-4745},
	isbn = {1530-6984},
	doi = {10.1021/nl402305n},
	author = {Mahmoud, M A and El-Sayed, M. A. and Gao, J. P. and Landman, U.}
}
@article {1386,
	title = {Hollow and Solid Metallic Nanoparticles in Sensing and in Nanocatalysis},
	journal = {Chemistry of Materials},
	volume = {26},
	number = {1},
	year = {2013},
	pages = {44-58},
	isbn = {0897-4756},
	author = {Mahmoud, Mahmoud A. and O{\textquoteright}Neil, Daniel and El-Sayed, Mostafa A.}
}
@article {1382,
	title = {Hollow gold nanorectangles: The roles of polarization and substrate},
	journal = {Journal of Chemical Physics},
	volume = {139},
	number = {4},
	year = {2013},
	note = {Near, Rachel D. El-Sayed, Mostafa A.},
	month = {Jul},
	isbn = {0021-9606},
	doi = {10.1063/1.4812931},
	author = {Near, R. D. and El-Sayed, M. A.}
}
@article {1392,
	title = {Inducing Cancer Cell Death by Targeting Its Nucleus: Solid Gold Nanospheres versus Hollow Gold Nanocages},
	journal = {Bioconjugate Chemistry},
	volume = {24},
	number = {6},
	year = {2013},
	note = {Mackey, Megan A. Saira, Farhat Mahmoud, Mahmoud A. El-Sayed, Mostafa A.},
	month = {Jun},
	pages = {897-906},
	isbn = {1043-1802},
	doi = {10.1021/bc300592d},
	author = {Mackey, M. A. and Saira, F. and Mahmoud, M A and El-Sayed, M. A.}
}
@article {1374,
	title = {The Last Step in Converting the Surface Plasmonic Energy into Heat by Nanocages and Nanocubes on Substrates},
	journal = {Small},
	volume = {9},
	number = {23},
	year = {2013},
	note = {Szymanski, Paul Mahmoud, Mahmoud A. El-Sayed, Mostafa A.},
	month = {Dec},
	pages = {3934-3938},
	isbn = {1613-6810},
	doi = {10.1002/smll.201300233},
	author = {Szymanski, P. and Mahmoud, M A and El-Sayed, M. A.}
}
@article {1347,
	title = {A New Nanotechnology Technique for Determining Drug Efficacy Using Targeted Plasmonically Enhanced Single Cell Imaging Spectroscopy},
	journal = {J Am Chem Soc},
	year = {2013},
	note = {MEDLINE AN 2013441929(Journal; Article; (JOURNAL ARTICLE))},
	month = {//},
	abstract = {Recently, we described a new technique, targeted plasmonically enhanced single cell imaging spectroscopy (T-PESCIS), which exploits the plasmonic properties of gold nanoparticles, e.g. gold nanospheres, to simultaneously obtain enhanced intracellular Raman molecular spectra and enhanced Rayleigh cell scattering images throughout the entire span of a single cell cycle. In the present work, we demonstrate the use of T-PESCIS in evaluating the relative efficacy and dynamics of two popular chemotherapy drugs on human oral squamous carcinoma (HSC-3) cells. T-PESCIS revealed three plasmonically enhanced Raman scattering vibration bands, 500, 1000, and 1585 cm(-1), associated with the cellular death dynamics. Detailed analysis indicated that the decrease in the 500 cm(-1) band did not correlate well with drug efficacy but could indicate death initiation. The time it takes for the relative intensity of either the 1000 or 1585 cm(-1) band ("SERS death" bands) to appear and increase to its maximum value after the injection of a known concentration of the drug can be related to the drug{\textquoteright}s efficacy. The inverse ratio, termed cell death enhancement factor, of these characteristic death times when using either band, especially the spectrally sharp band at 1000 cm(-1), gave the correct drug efficacy ratio as determined by the commonly used XTT cell viability assay method. These results strongly suggest the potential future use of this technique in determining the efficacy, dynamics, and molecular mechanisms of various drugs against different diseases.[on SciFinder (R)]},
	isbn = {1520-5126},
	author = {Austin, Lauren and Kang, Bin and El-Sayed, Mostafa A.}
}
@article {1396,
	title = {Plasmonic enhancement of photodynamic cancer therapy},
	journal = {Journal of Photochemistry and Photobiology a-Chemistry},
	volume = {269},
	year = {2013},
	note = {Hayden, Steven C. Austin, Lauren A. Near, Rachel D. Ozturk, Ramazan El-Sayed, Mostafa A.},
	month = {Oct},
	pages = {34-41},
	isbn = {1010-6030},
	doi = {10.1016/j.jphotochem.2013.06.004},
	author = {Hayden, S. C. and Austin, Lauren and Near, R. D. and Ozturk, R. and El-Sayed, M. A.}
}
@article {1351,
	title = {Probing the unique dehydration-induced structural modifications in cancer cell DNA using surface enhanced Raman spectroscopy},
	journal = {J Am Chem Soc},
	year = {2013},
	note = {MEDLINE AN 2013442001(Journal; Article; (JOURNAL ARTICLE))},
	month = {//},
	abstract = {Conformation-induced formation of a series of unique Raman marker bands in cancer cell DNA, upon dehydration, have been probed for the first time with the use of surface enhanced Raman spectroscopy (SERS). These bands are capable of distinguishing cancer cell DNA from healthy cell DNA. For this simple and label-free DNA detection approach, we used conventional spherical silver nanoparticles, at a high concentration, without any aggregating agents, which gave highly reproducible SERS spectra of DNA separated from various human cells irrespective of their highly complex compositions and sequences. The observed phenomenon is attributed to the change in the chemical environment due to the presence of nucleobase lesions in cancer cell DNA and subsequent variation in the nearby electronic cloud during the dehydration-driven conformational changes. Detailed analysis of the SERS spectra gives important insight about the lesion-induced structural modifications upon dehydration in the cancer cell DNA. These results have widespread implications in cancer diagnostics, where SERS provides vital information about the DNA modifications in the cancer cells.[on SciFinder (R)]},
	isbn = {1520-5126},
	author = {Panikkanvalappil, Sajanlal R. and Mackey, Megan A. and El-Sayed, Mostafa A.}
}
@article {1385,
	title = {Properties of pi-Conjugated Fluorescence Polymer-Plasmonic Nanoparticles Hybrid Materials (vol 116, 13336, 2012)},
	journal = {Journal of Physical Chemistry C},
	volume = {117},
	number = {9},
	year = {2013},
	note = {Mahmoud, M. A. Poncheri, A. J. El-Sayed, M. A. Bryant, J. Bunz, U.},
	month = {Mar},
	pages = {4876-4876},
	isbn = {1932-7447},
	doi = {10.1021/jp4006197},
	author = {Mahmoud, M A and Poncheri, A. J. and El-Sayed, M. A. and Bryant, J. and Bunz, U.}
}
@article {1380,
	title = {Rapid and Efficient Prediction of Optical Extinction Coefficients for Gold Nanospheres and Gold Nanorods},
	journal = {Journal of Physical Chemistry C},
	volume = {117},
	number = {45},
	year = {2013},
	note = {Near, Rachel D. Hayden, Steven C. Hunter, Ronald E., Jr. Thackston, Daniel El-Sayed, Mostafa A.},
	month = {Nov},
	pages = {23950-23955},
	isbn = {1932-7447},
	doi = {10.1021/jp4082596},
	author = {Near, R. D. and Hayden, S. C. and Hunter, R. E. and Thackston, D. and El-Sayed, M. A.}
}
@article {1390,
	title = {Substrate Effect on the Plasmonic Sensing Ability of Hollow Nanoparticles of Different Shapes},
	journal = {Journal of Physical Chemistry B},
	volume = {117},
	number = {16},
	year = {2013},
	note = {Mahmoud, Mahmoud A. El-Sayed, Mostafa A.Si},
	month = {Apr},
	pages = {4468-4477},
	isbn = {1520-6106},
	doi = {10.1021/jp3085793},
	author = {Mahmoud, M A and El-Sayed, M. A.}
}
@article {1348,
	title = {Surface Assembly and Plasmonic Properties in Strongly Coupled Segmented Gold Nanorods},
	journal = {Small},
	year = {2013},
	note = {MEDLINE AN 2013463112(Journal; Article; (JOURNAL ARTICLE))},
	month = {//},
	abstract = {An assembly strategy is reported such that segmented nanorods fabricated through template-assisted methods can be robustly transferred and tethered to a pre-functionalized substrate with excellent uniformity over large surface areas. After embedding the rods, sacrificial nickel segments were selectively etched leaving behind strongly coupled segmented gold nanorods with gaps between rods below 40 nm and as small as 2 nm. Hyper-spectral imaging is utilized to measure Rayleigh scattering spectra from individual and coupled nanorod elements in contrast to common bulk measurements. This approach discerns the effects of not only changing segment and gap size but also the presence of characteristic defects on the plasmonic coupling between closely spaced nanorods. Polarized hyper-spectral measurements are conducted to provide direct observation of the anisotropic plasmonic resonance modes in individual and coupled nanorods, which are close to those predicted by computer simulations for nanorods with ideal shapes. Some common deviations from ideal shape such as non-flat facets and asymmetric tails are demonstrated to result in the appearance of characteristic plasmon resonances, which have not been considered before. The large-scale assembly of coupled noble nanostructures with fine control over geometry and high uniformity provides means to strongly tune the scattering, absorption, and near-field plasmonic properties through the geometric arrangement of precisely controlled nanorod segments.[on SciFinder (R)]},
	isbn = {1613-6829},
	author = {Gupta, Maneesh K. and Konig, Tobias and Near, Rachel and Nepal, Dhriti and Drummy, Lawrence F. and Biswas, Sushmita and Naik, Swati and Vaia, Richard A. and El-Sayed, Mostafa A. and Tsukruk, Vladimir V.}
}
@article {1378,
	title = {Surface-Enhanced Raman Spectroscopy for Real-Time Monitoring of Reactive Oxygen Species-Induced DNA Damage and Its Prevention by Platinum Nanoparticles},
	journal = {Acs Nano},
	volume = {7},
	number = {9},
	year = {2013},
	note = {Panikkanvalappil, Sajanlal R. Mahmoud, Mahmoud A. Mackey, Megan A. El-Sayed, Mostafa A.},
	month = {Sep},
	pages = {7524-7533},
	isbn = {1936-0851},
	doi = {10.1021/nn403722x},
	author = {Panikkanvalappil, S. R. and Mahmoud, M A and Mackey, M. A. and El-Sayed, M. A.}
}
@article {1375,
	title = {Thermal/Electrochemical Growth and Characterization of One-Dimensional ZnO/TiO2 Hybrid Nanoelectrodes for Solar Fuel Production},
	journal = {Journal of Physical Chemistry C},
	volume = {117},
	number = {36},
	year = {2013},
	note = {Shaheen, Basamat S. Salem, Hanadi G. El-Sayed, Mostafa A. Allam, Nageh K.},
	month = {Sep},
	pages = {18502-18509},
	isbn = {1932-7447},
	doi = {10.1021/jp405515v},
	author = {Shaheen, B. S. and Salem, H. G. and El-Sayed, M. A. and Allam, N. K.}
}
@article {1381,
	title = {Thin to Thick, Short to Long: Spectral Properties of Gold Nanorods by Theoretical Modeling},
	journal = {Journal of Physical Chemistry C},
	volume = {117},
	number = {36},
	year = {2013},
	note = {Near, Rachel D. Hayden, Steven C. El-Sayed, Mostafa A.},
	month = {Sep},
	pages = {18653-18656},
	isbn = {1932-7447},
	doi = {10.1021/jp4078344},
	author = {Near, R. D. and Hayden, S. C. and El-Sayed, M. A.}
}
@article {1398,
	title = {Tissue Distribution and Efficacy of Gold Nanorods Coupled with Laser Induced Photoplasmonic Therapy in Ehrlich Carcinoma Solid Tumor Model},
	journal = {Plos One},
	volume = {8},
	number = {10},
	year = {2013},
	note = {El-Sayed, Mostafa A. Shabaka, Ali A. El-Shabrawy, Osama A. Yassin, Nemat A. Mahmoud, Sawsan S. El-Shenawy, Siham M. Al-Ashqar, Emad Eisa, Wael H. Farag, Niveen M. El-Shaer, Marwa A. Salah, Nabila Al-Abd, Ahmed M.},
	month = {Oct},
	abstract = {Gold nanorods (GNR) within tumor microregions are characterized by their ability to absorb near IR light and emit heat in what is called photoplasmonic effect. Yet, the efficacy of nanoparticles is limited due to intratumoral tissue distribution reasons. In addition, distribution of GNRs to normal tissue might result in non specific toxicity. In the current study, we are assessing the intratumoral and tissue distribution of PEGylated GNRs on the top of its antitumor characteristics when given intravenously or intratumoral to solid tumor bearing mice and coupled with laser photoplasmonic sessions. PEGylated GNRs with a longitudinal size of less than 100 nm were prepared with aspect ratio of 4.6 showing strong surface plasmon absorption at wavelength 800 nm. Pharmacokinetics of GNR after single I.V. administration (0.1 mg/kg) showed very short systemic circulating time (less than 3 h). On the other hand, tissue distribution of I.V. GNR (0.1 mg/kg) to normal animals showed preferential deposition in spleen tissue. Repeated administration of I.V. GNR resulted in preferential accumulation in both liver and spleen tissues. In addition, I.V. administration of GNR to Ehrlich carcinoma tumor bearing mice resulted in similar tissue distribution; tumor accumulation and anti-tumor effect compared to intratumoral administration. In conclusion, the concentration of GNR achieved within tumors microregions after I.V. administration was comparable to I.T. administration and sufficient to elicit tumoral growth arrest when coupled with laser-aided photoplasmonic treatment.},
	isbn = {1932-6203},
	doi = {10.1371/journal.pone.0076207},
	author = {El-Sayed, M. A. and Shabaka, A. A. and El-Shabrawy, O. A. and Yassin, N. A. and Mahmoud, S. S. and El-Shenawy, S. M. and Al-Ashqar, E. and Eisa, W. H. and Farag, N. M. and El-Shaer, M. A. and Salah, N. and Al-Abd, A. M.}
}
@proceedings {1383,
	title = {Towards a perfect system for solar hydrogen production: an example of synergy on the atomic scale},
	year = {2013},
	pages = {88220A-88220A-7},
	publisher = {International Society for Optics and Photonics},
	author = {Nashed, Ramy and Alamgir, Faisal M and Seung-Soon, Jang and Ismail, Yehea and El-Sayed, Mostafa A. and Allam, Nageh}
}
@proceedings {1377,
	title = {Toxicities and antitumor efficacy of tumor-targeted AuNRs in mouse model},
	volume = {73},
	number = {8},
	year = {2013},
	publisher = {AMER ASSOC CANCER RESEARCH 615 CHESTNUT ST, 17TH FLOOR, PHILADELPHIA, PA 19106-4404 USA},
	isbn = {0008-5472},
	author = {Peng, Xianghong and Mackey, Megan and Austin, Lauren and Oyelere, Adegboyega and Chen, Georgia and Huang, Xiaohua and El-Sayed, Mostafa A. and Shin, Dong M}
}
@article {1393,
	title = {Well-organized raspberry-like Ag@ Cu bimetal nanoparticles for highly reliable and reproducible surface-enhanced Raman scattering},
	journal = {Nanoscale},
	volume = {5},
	number = {23},
	year = {2013},
	pages = {11620-11624},
	author = {Lee, Jung-Pil and Chen, Dongchang and Li, Xiaxi and Yoo, Seungmin and Bottomley, Lawrence A and El-Sayed, Mostafa A. and Park, Soojin and Liu, Meilin}
}
@article {1340,
	title = {5-Fluorouracil induces plasmonic coupling in gold nanospheres: new generation of chemotherapeutic agents},
	journal = {J. Nanomed. Nanotechnol.},
	volume = {3},
	number = {7},
	year = {2012},
	note = {CAPLUS AN 2012:1822923(Journal; Online Computer File)},
	month = {//},
	pages = {1000146/1-1000146/7},
	publisher = {OMICS Publishing Group},
	type = {10.4172/2157-7439.1000146},
	abstract = {Loading 5- Fluorouracil (5-FU) into gold nanoparticles (AuNPs) could enhance its activity as anticancer drug hugely by enhancing its ability for penetration through the cell membrane. Accordingly, this work is devoted to loading 5-FU into AuNPs surface and studying the binding mechanism of the drug to the surface of the gold nanoparticles. Our finding indicates that new absorption band appears at longer wavelength upon loading 5-FU into gold nanospheres capped with citrate. This near IR band is due to induced surface plasmon coupling via hydrogen bonding between 5-FU and surface capping AuNPs. This leads to great enhancement of the drug action as chemotherapeutic as well as photothermal agents. Factors which affect the binding between 5-FU and the AuNPs such as pH, time after mixing the drug with AuNPs, concn. of the 5-FU, have been studied in detail. Accordingly, the binding interaction is proven to be via hydrogen bonding. Upon the investigation of thermal and photo satiability, the formed composite 5-FU@ AuNPs showed high stability towards these factors. The spectral and morphol. studies were measured via UV-VIS spectroscopy and Transmission Electron Microscopy (HR-TEM). Remarkable increases in the drug anticancer activity upon loading into AuNPs were obsd. for the cell viability test of human colon cancer (HCT16). [on SciFinder(R)]},
	isbn = {2157-7439},
	doi = {10.4172/2157-7439.1000146},
	author = {Mohamed, Mona B. and Adbel-Ghani, Nour T. and El-Borady, Ola M. and El-Sayed, Mostafa A.}
}
@article {1331,
	title = {Aggregation and Interaction of Cationic Nanoparticles on Bacterial Surfaces},
	journal = {Journal of the American Chemical Society},
	volume = {134},
	number = {16},
	year = {2012},
	note = {Times Cited: 1Hayden, Steven C. Zhao, Gengxiang Saha, Krishnendu Phillips, Ronnie L. Li, Xiaoning Miranda, Oscar R. Rotello, Vincent M. El-Sayed, Mostafa A. Schmidt-Krey, Ingeborg Bunz, Uwe H. F.},
	month = {Apr},
	pages = {6920-6923},
	abstract = {Cationic monolayer-protected gold nanoparticles (AuNPs) with sizes of 6 or 2 nm interact with the cell membranes of Escherichia coli (Gram-) and Bacillus subtilis (Gram+), resulting in the formation of strikingly distinct AuNP surface aggregation patterns or lysis depending upon the size of the AuNPs. The aggregation phenomena were investigated by transmission electron microscopy and UV-vis spectroscopy. Upon proteolytic treatment of the bacteria, the distinct aggregation patterns disappeared.},
	isbn = {0002-7863},
	doi = {10.1021/ja301167y},
	author = {Hayden, S. C. and Zhao, G. X. and Saha, K. and Phillips, R. L. and Li, X. N. and Miranda, O. R. and Rotello, V. M. and El-Sayed, M. A. and Schmidt-Krey, I. and Bunz, U. H. F.}
}
@article {1329,
	title = {Antiandrogen Gold Nanoparticles Dual-Target and Overcome Treatment Resistance in Hormone-Insensitive Prostate Cancer Cells},
	journal = {Bioconjugate Chemistry},
	volume = {23},
	number = {8},
	year = {2012},
	note = {Times Cited: 0Dreaden, Erik C. Gryder, Berkley E. Austin, Lauren A. Defo, Brice A. Tene Hayden, Steven C. Pi, Min Quarles, L. Darryl Oyelere, Adegboyega K. El-Sayed, Mostafa A.},
	month = {Aug},
	pages = {1507-1512},
	abstract = {prostate cancer is the most commonly diagnosed cancer among men in the developed countries.(1) One in six males in the U.S.(2) and one in nine males in the U.K.(3) will develop the disease at some point during their lifetime. Despite advances in prostate cancer screening, more than a quarter of a million men die from the disease every year(1) due primarily to treatment-resistance and metastasis. Colloidal nanotechnologies can provide tremendous enhancements to existing targeting/treatment strategies for prostate cancer to which malignant cells are less sensitive. Here, we show that antiandrogen gold nanoparticles-multivalent analogues of antiandrogens currently used in clinical therapy for prostate cancer-selectively engage two distinct receptors, androgen receptor (AR), a target for the treatment of prostate cancer, as well as a novel G-protein coupled receptor, GPRC6A, that is also upregulated in prostate cancer. These nanoparticles selectively accumulated in hormone-insensitive and chemotherapy resistant prostate cancer cells, bound androgen receptor with multivalent affinity, and exhibited greatly enhanced drug potency versus monovalent antiandrogens currently in clinical use Further, antiandrogen gold nanoparticles selectively stimulated GPRC6A with multivalent affinity, demonstrating that the delivery of nanoscale antiandrogens can also be facilitated by the transmembrane receptor in order to realize increasingly selective, increasingly potent therapy for treatment-resistant prostate cancers.},
	isbn = {1043-1802},
	doi = {10.1021/bc300158k},
	author = {Dreaden, E. C. and Gryder, B. E. and Austin, Lauren and Defo, B. A. T. and Hayden, S. C. and Pi, M. and Quarles, L. D. and Oyelere, A. K. and El-Sayed, M. A.}
}
@article {1333,
	title = {Application of surface enhanced Raman spectroscopy to the study of SOFC electrode surfaces},
	journal = {Physical Chemistry Chemical Physics},
	volume = {14},
	number = {17},
	year = {2012},
	note = {Times Cited: 3Li, Xiaxi Blinn, Kevin Fang, Yingcui Liu, Mingfei Mahmoud, Mahmoud A. Cheng, Shuang Bottomley, Lawrence A. El-Sayed, Mostafa Liu, Meilin},
	pages = {5919-5923},
	abstract = {SERS provided by sputtered silver was employed to detect trace amounts of chemical species on SOFC electrodes. Considerable enhancement of Raman signal and lowered detection threshold were shown for coked nickel surfaces, CeO2 coatings, and cathode materials (LSM and LSCF), suggesting a viable approach to probing electrode degradation and surface catalytic mechanism.},
	isbn = {1463-9076},
	doi = {10.1039/c2cp40091j},
	author = {Li, X. X. and Blinn, K. and Fang, Y. C. and Liu, M. F. and Mahmoud, M A and Cheng, S. and Bottomley, L. A. and El-Sayed, M. and Liu, M. L.}
}
@article {1328,
	title = {Detecting and Destroying Cancer Cells in More than One Way with Noble Metals and Different Confinement Properties on the Nanoscale},
	journal = {Accounts of Chemical Research},
	volume = {45},
	number = {11},
	year = {2012},
	note = {Times Cited: 0Dreaden, Erik C. El-Sayed, Mostafa A.Si},
	month = {Dec},
	pages = {1854-1865},
	abstract = {Today, 1 in 2 males and 1 in 3 females in the United States will develop cancer at some point during their lifetimes, and 1 in 4 males and 1 in 5 females in the United States will die from the disease. New methods for detection and treatment have dramatically improved dancer care in the United States. However, as improved detection and increasing exposure to carcinogens has led to higher rates of cancer incidence, dinidans and researchers have not balanced that increase with a similar decrease in cancer mortality rates. This mismatch highlights a dear and urgent need for increasingly potent and selective methods with which to detect and treat cancers at their earliest stages. Nanotechnology, the use of materials with structural features ranging from 1 to 100 nm in size, has dramatically altered the design, use, and delivery of cancer diagnostic and therapeutic agents. The unique and newly discovered properties of these structures can enhance the specificities with which biomedical agents are delivered, complementing their efficacy or diminishing unintended side effects. Gold (and silver) nanotechnologies afford a particularly unique set of physiological and optical properties which can be leveraged In applications ranging from in vitro/vivo therapeutics and drug delivery to imaging and diagnostics, surgical guidance, and treatment monitoring. Nanoscale diagnostic and therapeutic agents have been in use since the development of micellar nanocarriers and polymer drug nanoconjugates in the mid-1950s, liposomes by Bangham and Watkins in the mid-1960s, and the introduction of polymeric nanoparticles by Langer and Folkman in 1976. Since then, nanoscale constructs such as dendrimers, protein nanoconjugates, and inorganic nanoparticles have been developed for the systemic delivery of agents to specific disease sites. Today, more than 20 FDA-approved diagnostic or therapeutic nanotechnologies are in clinical use with roughly 250 others in clinical development The global market for nano-enabled medical technologies is expected to grow to $70-160 billion by 2015, rivaling the current market share of biologics worldwide. In this Account, we explore the emerging applications of noble metal nanotechnologies in cancer diagnostics and therapeutics carried out by our group and by others. Many of the novel biomedical properties associated with gold and silver nanoparticles arise from confinement effects: (i) the confinement of photons within the particle which can lead to dramatic electromagnetic scattering and absorption (useful in sensing and heating applications, respectively); (ii) the confinement of molecules around the nanoparticle (useful in drug delivery); and (iii) the cellular/subcellular confinement of particles within malignant cells (such as selective, nuclear-targeted cytotoxic DNA damage by gold nanoparticles). We then describe how these confinement effects relate to specific aspects of diagnosis and treatment such as (i) laser photothermal therapy, optical scattering microscopy, and spectroscopic detection, (ii) drug targeting and delivery, and (iii) the ability of these structures to act as intrinsic therapeutic agents which can selectively perturb/inhibit cellular functions such as division. We intend to provide the reader with a unique physical and chemical perspective on both the design and application of these technologies in cancer diagnostics and therapeutics. We also suggest a framework for approaching future research in the field.},
	isbn = {0001-4842},
	doi = {10.1021/ar2003122},
	author = {Dreaden, E. C. and El-Sayed, M. A.}
}
@article {1339,
	title = {Different Methods of Increasing the Mechanical Strength of Gold Nanocages},
	journal = {Journal of Physical Chemistry Letters},
	volume = {3},
	number = {23},
	year = {2012},
	note = {Times Cited: 0Mahmoud, Mahmoud A. Szymanski, Paul El-Sayed, Mostafa A.},
	month = {Dec},
	pages = {3527-3531},
	abstract = {Using the ultrafast coherent modulation of the surface plasmon band intensity with the totally symmetric lattice vibration of gold nanocages, we were able to determine and use their frequencies as a measure of the cage{\textquoteright}s mechanical stability. The presence of an inner "stiff" transition-metal nanoshell with a higher value of the elastic modulus is found to increase the frequency of the lattice vibration of the outer soft gold nanoshell. This could also explain the observed increase in both the gold lattice vibrational frequency as well as the lattice vibration relaxation time in the Au-Pt and Au-Pd double-shell nanocages. It is also found that when these nanoparticles are assembled into monolayers on quartz substrates by the Langmuir-Blodgett technique, the oscillation frequency of the gold shell with the transition metal having the largest elastic constant suffers the least change in its oscillation frequency as a result of its resistance to distortion as a result of binding to the substrate.},
	isbn = {1948-7185},
	doi = {10.1021/jz301503z},
	author = {Mahmoud, M A and Szymanski, P. and El-Sayed, M. A.}
}
@article {1335,
	title = {Effect of the Dielectric Constant of the Surrounding Medium and the Substrate on the Surface Plasmon Resonance Spectrum and Sensitivity Factors of Highly Symmetric Systems: Silver Nanocubes},
	journal = {Journal of the American Chemical Society},
	volume = {134},
	number = {14},
	year = {2012},
	note = {Times Cited: 3Mahmoud, Mahmoud A. Chamanzar, Maysamreza Adibi, Ali El-Sayed, Mostafa A.},
	month = {Apr},
	pages = {6434-6442},
	abstract = {Silver nanocubes (AgNCs), 60 nm, have four extinction surface plasmon resonance (SPR) peaks. The finite difference time domain (FDTD) simulation method is used to assign the absorption and scattering peaks and also to calculate the plasmon field intensity for AgNCs. Because AgNCs have a highly symmetric cubic shape, there is a uniform distribution of the plasmon field around them, and they are thus sensitive to asymmetric dielectric perturbations. When the dielectric medium around a nanoparticle is changed anisotropically, either by placing the particle on a substrate or by coating it asymmetrically with a solvent, the plasmon field is distorted, and the plasmonic absorption and scattering spectra could shift differently. For the 60 nm AgNC, we found that the scattering resonance peak shifted more than the absorption peak. This changes the extinction bandwidth of these overlapping absorption and scattering bands, and consequently the figure of merit of the nanoparticle, as a localized SPR sensor, no longer has a constant value.},
	isbn = {0002-7863},
	doi = {10.1021/ja300901e},
	author = {Mahmoud, M A and Chamanzar, M. and Adibi, A. and El-Sayed, M. A.}
}
@article {1341,
	title = {Extinction vs Absorption: Which Is the Indicator of Plasmonic Field Strength for Silver Nanocubes?},
	journal = {Journal of Physical Chemistry C},
	volume = {116},
	number = {43},
	year = {2012},
	note = {Times Cited: 0Near, Rachel Hayden, Steven El-Sayed, Mostafa},
	month = {Nov},
	pages = {23019-23026},
	abstract = {This investigation demonstrates the contributions of absorption and scattering to the extinction spectrum of silver nanocubes with multipole resonances and the complexity of the resulting plasmon field strengths for these varying modes. The three-dimensional plasmonic field distribution and orientation around a silver nanosphere (AgNS; 40 nm) and a silver nanocube (AgNC; 40, 60, 86 nm) were calculated in the visible via the discrete dipole approximation. The three-dimensional nature of these particles allows for significant contribution from the quadrupole mode in some cases. The AgNS displays one plasmon band, its dipole mode, and has little contribution from scattering. The maximum plasmon field occurs at the extinction maximum, as expected. The 40 nm AgNC exhibits multiple plasmon bands, and the highest maximum field strength is attained from excitation of the quadrupole mode, not the dipole mode. As the size of the AgNC increases, the contribution from scattering increases. When the contribution from scattering is greater than the contribution from absorption in a AgNC, the field strength within a plasmon mode trends with the absorption and not with the extinction or cattering. This should be considered in applications of AgNCs, as excitation of the largest peak in the experimental extinction spectrum will not always result in the strongest plasmon field strength.},
	isbn = {1932-7447},
	doi = {10.1021/jp309272b},
	author = {Near, R. and Hayden, S. and El-Sayed, M.}
}
@article {1326,
	title = {The golden age: gold nanoparticles for biomedicine},
	journal = {Chemical Society Reviews},
	volume = {41},
	number = {7},
	year = {2012},
	note = {Times Cited: 54Dreaden, Erik C. Alkilany, Alaaldin M. Huang, Xiaohua Murphy, Catherine J. El-Sayed, Mostafa A.},
	pages = {2740-2779},
	abstract = {Gold nanoparticles have been used in biomedical applications since their first colloidal syntheses more than three centuries ago. However, over the past two decades, their beautiful colors and unique electronic properties have also attracted tremendous attention due to their historical applications in art and ancient medicine and current applications in enhanced optoelectronics and photovoltaics. In spite of their modest alchemical beginnings, gold nanoparticles exhibit physical properties that are truly different from both small molecules and bulk materials, as well as from other nanoscale particles. Their unique combination of properties is just beginning to be fully realized in range of medical diagnostic and therapeutic applications. This critical review will provide insights into the design, synthesis, functionalization, and applications of these artificial molecules in biomedicine and discuss their tailored interactions with biological systems to achieve improved patient health. Further, we provide a survey of the rapidly expanding body of literature on this topic and argue that gold nanotechnology-enabled biomedicine is not simply an act of {\textquoteright}gilding the (nanomedicinal) lily{\textquoteright}, but that a new {\textquoteright}Golden Age{\textquoteright} of biomedical nanotechnology is truly upon us. Moving forward, the most challenging nanoscience ahead of us will be to find new chemical and physical methods of functionalizing gold nanoparticles with compounds that can promote efficient binding, clearance, and biocompatibility and to assess their safety to other biological systems and their long-term term effects on human health and reproduction (472 references).},
	isbn = {0306-0012},
	doi = {10.1039/c1cs15237h},
	author = {Dreaden, E. C. and Alkilany, A. M. and Huang, X. H. and Murphy, C. J. and El-Sayed, M. A.}
}
@article {1337,
	title = {Metallic Double Shell Hollow Nanocages: The Challenges of Their Synthetic Techniques},
	journal = {Langmuir},
	volume = {28},
	number = {9},
	year = {2012},
	note = {Times Cited: 5Mahmoud, M. A. El-Sayed, M. A.},
	month = {Mar},
	pages = {4051-4059},
	abstract = {Hollow metallic nanoparticles have been attracting the attention of many researchers in the past five years due to their new properties and potential applications. The unique structure of the hollow nanoparticles; presence of two surfaces (internal and external), and the presence of both cavities and pores in the wall surfaces of these nanoparticles are responsible for their unique properties and applications. Here the galvanic replacement technique is used to prepare nanocages made of gold, platinum, and palladium. In addition, hollow double shell nanoparticles are made of two metal shells like Au-Pt, Pt-Au, Au-Pd, Pd-Au, Pd-Pt, and Pt-Pd. Silver nanocubes are used as templates during the synthesis of hollow nanoparticles with single metal shell or double shell nanocages. Most of the problems that could affect the synthesis of solid Silver nanocubes used as template as well as the double shell nanocages and their possible solutions are discussed in a detail. The sizes and shapes of the single-shell and double-shell nanocages were characterized by a regular and high-resolution TEM. A SEM mapping technique is also used to image the surface atoms for the double shell hollow nanoparticles in order to determine the thickness of the two metal shells. In addition, optical studies are used to monitor the effect of the dielectric properties of the other metals on the plasmonic properties of the gold nanoshell in these mixed nanoparticles.},
	isbn = {0743-7463},
	doi = {10.1021/la203982h},
	author = {Mahmoud, M A and El-Sayed, M. A.}
}
@article {1417,
	title = {Nano and Molecular Science and Technology Special Issue Honoring Paul Barbara},
	journal = {Accounts of Chemical Research},
	volume = {45},
	number = {11},
	year = {2012},
	month = {2012/11/20},
	pages = {1842-1843},
	publisher = {American Chemical Society},
	isbn = {0001-4842},
	doi = {10.1021/ar300271q},
	author = {El-Sayed, Mostafa and Masuhara, Hiroshi and Pileni, Marie-Paule and Landes, Christy}
}
@article {1345,
	title = {Nanocatalysts Can Change the Number of Electrons Involved in Oxidation-Reduction Reaction with the Nanocages Being the Most Efficient},
	journal = {Journal of Physical Chemistry C},
	volume = {116},
	number = {45},
	year = {2012},
	note = {Times Cited: 0Weng, Guojun Mahmoud, Mahmoud A. El-Sayed, Mostafa A.},
	month = {Nov},
	pages = {24171-24176},
	abstract = {Eosin Y (EY) is a fluorescein derivative dye that can be reduced by accepting either one or two electrons. The one- or two electron reduction potentials have comparable values. The two-electron reduction pathway dominates when sodium borohydride is used, whereas the reduction pathway changes to a one-electron reduction pathway when gold solid (AuNS) or hollow (AuHS) nanosphere catalysts are used. The reduction reaction of EY by borohydride proceeds via one kinetic stage, whereas in the presence of gold nanocatalysts, three different stages are identified. The first stage has the same reaction rate as in the absence of the nanocatalyst, and no one-electron product is observed (absorption peak at 405 nm). The second stage starts when the rate of the disappearance of EY is suddenly increased; a new peak at 405 nm beings to appear. This stage ends when the rate of the disappearance of EY decreases. The third stage has a rate close to that of the first stage, and the EY is reduced again by accepting two electrons. The lifetime of the first stage is greatly affected by the concentration of the nanocatalyst and decreases as the concentration of the nanocatalyst is increased. The conversion ratio of EY to its one electron reduced form is found to increase proportionally with the concentration of the gold nanocatalyst. In the case of using hollow nanospheres as a catalyst, the conversion ratio is found to be 3 times higher than that when using the solid nanospheres due to the cage effect.},
	isbn = {1932-7447},
	doi = {10.1021/jp308869m},
	author = {Weng, G. and Mahmoud, M A and El-Sayed, M. A.}
}
@article {1415,
	title = {The one dimensional photofragment translational spectroscopic technique: intramolecular clocking of energy redistribution for molecules falling apart1},
	journal = {Time-of-Flight Mass Spectrometry and its Applications},
	year = {2012},
	pages = {265},
	isbn = {0444596186},
	author = {Hwangl, Hyun Jin and Grifliths, Jennifer and El-Sayed, M. A.}
}
@article {1343,
	title = {Photoelectric Conversion Properties of Dye-Sensitized Solar Cells Using Dye-Dispersing Titania},
	journal = {Journal of Physical Chemistry C},
	volume = {116},
	number = {7},
	year = {2012},
	note = {Times Cited: 1Nishikiori, Hiromasa Uesugi, Yohei Setiawan, Rudi Agus Fujii, Tsuneo Qian, Wei El-Sayed, Mostafa A.},
	month = {Feb},
	pages = {4848-4854},
	abstract = {The time-resolved fluorescence and photoelectrochemical properties of dye-sensitized solar cells using crystalline titania electrodes coated with N3 dye-dispersing amorphous titania gel were investigated to clarify the influence of the dye titania interaction and electron transfer on their photoelectric conversion performance. The photocurrent quantum efficiency of the electrodes was remarkably increased by a steam treatment due to the crystallization and densification of the amorphous titania layer compared to that of the untreated electrode. The electron injection from the dye to the crystalline titania foundation via the steam-treated titania dispersing the dye was confirmed to be more efficient than that in the conventional electrodes. The dye-dispersing titania layer prevented interaction between the dye molecules and back electron transfer from the titania to the electrolyte. The charge separation and photoelectric conversion performance of the dye-sensitized solar cells were improved by forming the specific dye-dispersing titania layer.},
	isbn = {1932-7447},
	doi = {10.1021/jp2094388},
	author = {Nishikiori, H. and Uesugi, Y. and Setiawan, R. A. and Fujii, T. and Qian, W. and El-Sayed, M. A.}
}
@article {1342,
	title = {Pronounced Effects of Anisotropy on Plasmonic Properties of Nanorings Fabricated by Electron Beam Lithography},
	journal = {Nano Letters},
	volume = {12},
	number = {4},
	year = {2012},
	note = {Times Cited: 3Near, Rachel Tabor, Christopher Duan, Jinsong Pachter, Ruth El-Sayed, Mostafa},
	month = {Apr},
	pages = {2158-2164},
	abstract = {Gold nanoring dimers were fabricated via EBL with dimensions of 127.6 +/- 2.5 and 57.8 +/- 2.3 nm for the outer and inner diameters, respectively, with interparticle separations ranging from 17.8 +/- 3.4 to 239.2 +/- 3.7 nm. The coupling between the inner and outer surfaces of a single nanoring renders it very sensitive to any anisotropy. We found that anisotropy in the particle geometry and anisotropy introduced by the substrate combine to create very unique spectral features in this system.},
	isbn = {1530-6984},
	doi = {10.1021/nl300622p},
	author = {Near, R. and Tabor, C. and Duan, J. S. and Pachter, R. and El-Sayed, M.}
}
@article {1338,
	title = {Properties of pi-Conjugated Fluorescence Polymer-Plasmonic Nanoparticles Hybrid Materials},
	journal = {Journal of Physical Chemistry C},
	volume = {116},
	number = {24},
	year = {2012},
	note = {Times Cited: 1Mahmoud, M. A. Poncheri, A. J. El-Sayed, M. A.},
	month = {Jun},
	pages = {13336-13342},
	abstract = {Recently, great interest has risen in studying and using hybrid material made by mixing polymeric materials with plasmonic nanoparticles. In the present work, the photophysical properties of two poly(p-phenyleneethynylene) fluorescent polymers, varying in chain length, were studied as a function of (1) pure polymer surface compression after deposition from a Langmuir-Blodgett trough onto a substrate and (2) deposition of a constant amount of polymer onto the surface of silver nanocube arrays of varying particle densities. The results are discussed in terms of the surface pressure and nanoparticle topography effects on conformation of the fluorescent polymer. It was found that the short polymer is much less affected by increased surface pressure, remaining isolated from interchain interaction. The long polymer exhibits signs of conjugation breaking, presumably due to compression of its longer, "tangled", structure. The two polymer chains in the nanoparticle/polymer series of experiments exhibited a blue-shift and a substantial narrowing of their emission spectra when deposited onto the lowest surface pressure nanoparticle sample. With increasing nanoparticle density, the spectra continue to blue-shift and narrow. This effect is presumably a combined effect of conformational changes that shift the emission to higher energy (blue-shift) and plasmonic effects that result in enhancement of primary emission of the polymer (emission from the 0-0 and 1-0 transitions), thus narrowing the emission.},
	isbn = {1932-7447},
	doi = {10.1021/jp303908e},
	author = {Mahmoud, M A and Poncheri, A. J. and El-Sayed, M. A.}
}
@article {1332,
	title = {Real-Time Molecular Imaging throughout the Entire Cell Cycle by Targeted Plasmonic-Enhanced Rayleigh/Raman Spectroscopy},
	journal = {Nano Letters},
	volume = {12},
	number = {10},
	year = {2012},
	note = {Times Cited: 0Kang, Bin Austin, Lauren A. El-Sayed, Mostafa A.},
	month = {Oct},
	pages = {5369-5375},
	abstract = {Due to their strong enhancement of scattered light, plasmonic nanoparticles have been utilized for various biological and medical applications. Here, we describe a new technique, Targeted Plasmonic-Enhanced Single-Cell Rayleigh/Raman Spectroscopy, to monitor the molecular changes of any cell-component, such as the nucleus, during the different phases of its full cell cycle by simultaneously recording its Rayleigh images and Raman vibration spectra in real-time. The analysis of the observed Raman DNA and protein peaks allowed the different phases of the cell cycle to be identified. This technique could be used for disease diagnostics and potentially improve our understanding of the molecular mechanisms of cellular functions such as division, death, signaling, and drug action.},
	isbn = {1530-6984},
	doi = {10.1021/nl3027586},
	author = {Kang, B. and Austin, Lauren and El-Sayed, M. A.}
}
@article {1327,
	title = {Size matters: gold nanoparticles in targeted cancer drug delivery},
	journal = {Ther. Delivery},
	volume = {3},
	number = {4},
	year = {2012},
	note = {CAPLUS AN 2012:489934(Journal; General Review; Online Computer File)},
	month = {//},
	pages = {457-478},
	publisher = {Future Science Ltd.},
	type = {10.4155/tde.12.21},
	abstract = {A review. Cancer is the current leading cause of death worldwide, responsible for approx. one quarter of all deaths in the USA and UK. Nanotechnologies provide tremendous opportunities for multimodal, site-specific drug delivery to these disease sites and Au nanoparticles further offer a particularly unique set of phys., chem. and photonic properties with which to do so. This review will highlight some recent advances, by our lab. and others, in the use of Au nanoparticles for systemic drug delivery to these malignancies and will also provide insights into their rational design, synthesis, physiol. properties and clin./preclin. applications, as well as strategies and challenges toward the clin. implementation of these constructs moving forward. [on SciFinder(R)]},
	keywords = {review gold nanoparticle targeted cancer drug delivery},
	isbn = {2041-5990},
	doi = {10.4155/tde.12.21},
	author = {Dreaden, Erik C. and Austin, Lauren and Mackey, Megan A. and El-Sayed, Mostafa A.}
}
@article {1330,
	title = {Small Molecule-Gold Nanorod Conjugates Selectively Target and Induce Macrophage Cytotoxicity towards Breast Cancer Cells},
	journal = {Small},
	volume = {8},
	number = {18},
	year = {2012},
	note = {Times Cited: 0Dreaden, Erik C. Mwakwari, Sandra C. Austin, Lauren A. Kieffer, Matthew J. Oyelere, Adegboyega K. El-Sayed, Mostafa A.},
	month = {Sep},
	pages = {2819-2822},
	isbn = {1613-6810},
	doi = {10.1002/smll.201200333},
	author = {Dreaden, E. C. and Mwakwari, S. C. and Austin, Lauren and Kieffer, M. J. and Oyelere, A. K. and El-Sayed, M. A.}
}
@article {1344,
	title = {Some recent developments in photoelectrochemical water splitting using nanostructured TiO2: a short review},
	journal = {Theoretical Chemistry Accounts},
	volume = {131},
	number = {6},
	year = {2012},
	note = {Times Cited: 0Szymanski, Paul El-Sayed, Mostafa A.},
	month = {Jun},
	abstract = {Photoelectrochemical cells with TiO2 electrodes to convert sunlight and water into gaseous hydrogen and oxygen are a source of clean and renewable fuel. Despite their great potential, far-from-ideal performance and poor utilization of the solar spectrum have prevented them from becoming a widespread and practical technology. We review recent experimental work that uses dynamics measurements to study limitations of photoelectrochemical cells from a fundamental level and the use of TiO2 nanotube arrays as a superior alternative to TiO2 nanoparticles. Through a combination of nanoscale size control, doping, composite materials, and the incorporation of noble-metal nanoparticles, improved performance and light harvesting are demonstrated.},
	isbn = {1432-881X},
	doi = {10.1007/s00214-012-1202-2},
	author = {Szymanski, P. and El-Sayed, M. A.}
}
@article {1423,
	title = {Synthesis and Optical Properties of Small Au Nanorods Using a Seedless Growth Technique},
	journal = {Langmuir},
	volume = {28},
	year = {2012},
	month = {Jun},
	pages = {9807-9815},
	abstract = {Gold nanoparticles have shown potential in photothermal cancer therapy and optoelectronic technology. In both applications, a call for small size nanorods is warranted. In the present work, a one-pot seedless synthetic technique has been developed to prepare relatively small monodisperse gold nanorods with average dimensions (length x width) of 18 x 4.5 nm, 25 x 5 nm, 15 x 4.5 nm, and 10 x 2.5 nm. In this method, the pH was found to play a crucial role in the monodispersity of the nanorods when the NaBH4 concentration of the growth solution was adjusted to control the reduction rate of the gold ions. At the optimized pH and NaBH4 concentrations, smaller gold nanorods were produced by adjusting the CTAB concentration in the growth solution. In addition, the concentration of silver ions in the growth solution was found to be pivotal in controlling the aspect ratio of the nanorods. The extinction coefficient values for the small gold nanorods synthesized with three different aspect ratios were estimated using the absorption spectra, size distributions, and the atomic spectroscopic analysis data. The previously accepted relationships between the extinction coefficient or the longitudinal band wavelength values and the nanorods{\textquoteright} aspect ratios found for the large nanorods do not extend to the small size domain reported in the present work. The failure of extending these relationships over larger sizes is a result of the interaction of light with the large rods giving an extinction band which results mostly from scattering processes while the extinction of the small nanorods results from absorption processes.},
	isbn = {0743-7463},
	doi = {10.1021/la301387p},
	author = {Ali, M. R. K. and Snyder, B. and El-Sayed, M. A.}
}
@article {1324,
	title = {Synthesis and Optical Properties of Small Au Nanorods Using a Seedless Growth Technique},
	journal = {Langmuir},
	volume = {28},
	number = {25},
	year = {2012},
	note = {Times Cited: 2Ali, Moustafa R. K. Snyder, Brian El-Sayed, Mostafa A.},
	month = {Jun},
	pages = {9807-9815},
	abstract = {Gold nanoparticles have shown potential in photothermal cancer therapy and optoelectronic technology. In both applications, a call for small size nanorods is warranted. In the present work, a one-pot seedless synthetic technique has been developed to prepare relatively small monodisperse gold nanorods with average dimensions (length x width) of 18 x 4.5 nm, 25 x 5 nm, 15 x 4.5 nm, and 10 x 2.5 nm. In this method, the pH was found to play a crucial role in the monodispersity of the nanorods when the NaBH4 concentration of the growth solution was adjusted to control the reduction rate of the gold ions. At the optimized pH and NaBH4 concentrations, smaller gold nanorods were produced by adjusting the CTAB concentration in the growth solution. In addition, the concentration of silver ions in the growth solution was found to be pivotal in controlling the aspect ratio of the nanorods. The extinction coefficient values for the small gold nanorods synthesized with three different aspect ratios were estimated using the absorption spectra, size distributions, and the atomic spectroscopic analysis data. The previously accepted relationships between the extinction coefficient or the longitudinal band wavelength values and the nanorods{\textquoteright} aspect ratios found for the large nanorods do not extend to the small size domain reported in the present work. The failure of extending these relationships over larger sizes is a result of the interaction of light with the large rods giving an extinction band which results mostly from scattering processes while the extinction of the small nanorods results from absorption processes.},
	isbn = {0743-7463},
	doi = {10.1021/la301387p},
	author = {Ali, M. R. K. and Snyder, B. and El-Sayed, M. A.}
}
@article {1334,
	title = {The unusual fluorescence intensity enhancement of poly(p-phenyleneethynylene) polymer separated from the silver nanocube surface by H-bonded LbL shells},
	journal = {Journal of Materials Chemistry},
	volume = {22},
	number = {33},
	year = {2012},
	note = {Times Cited: 0Lisunova, Milana Mahmoud, Mahmoud Holland, Neal Combs, Zachary A. El-Sayed, Mostafa A. Tsukruk, Vladimir V.},
	pages = {16745-16753},
	abstract = {The fluorescence intensity of poly(p-phenyleneethynylene) (PPE) polymer separated from the surface of plasmonic silver nanocubes (47 nm AgNCs) is measured by varying the number of layers of polyvinyl pyrrolidone (PVPON) and polymethyl acrylic acid (PMAA), n. The shell thickness is sensitive to the solvent due to the formation of a solvent-sensitive hydrogen bonding network. The fluorescent behavior of the PPE on the core-shell PPE-(PVPON-PMAA) n-AgNCs structures fabricated here was evaluated as a function of n as well as the nature of the surrounding solvent. Surprisingly, the fluorescence intensity of the outer PPE shell is found to increase dramatically (by more than an order of magnitude) as its separation from the nanoparticle surface increases and then decreases at a distance that depends upon the swelling behavior of the polymer shells. The distance for the highest fluorescence enhancement was found to be 20.0 nm and 24.0 nm, in water and ethanol respectively. The observed change in the fluorescence intensity of the PPE polymer with increasing its separation from the plasmonic surface is proposed to result from the interplay between a short range quenching mechanism and a relatively long-range plasmonic fluorescence enhancing mechanism. DDA calculations gave support to the significant contribution of the latter mechanism.},
	isbn = {0959-9428},
	doi = {10.1039/c2jm32450d},
	author = {Lisunova, M. and Mahmoud, M. and Holland, N. and Combs, Z. A. and El-Sayed, M. A. and Tsukruk, V. V.}
}
@article {1086,
	title = {Bacteriorhodopsin/TiO(2) nanotube arrays hybrid system for enhanced photoelectrochemical water splitting},
	journal = {Energy \& Environmental Science},
	volume = {4},
	number = {8},
	year = {2011},
	note = {Allam, Nageh K. Yen, Chun-Wan Near, Rachel D. El-Sayed, Mostafa A.},
	month = {Aug},
	pages = {2909-2914},
	abstract = {In recent years, considerable efforts have been made to improve the performance of photoactive nanostructured materials for water splitting applications. Herein, we report on the assembly and use of a bacteriorhodopsin (bR)/TiO(2) nanotube array hybrid electrode system. Photoanode materials composed of similar to 7 mu m long self-ordered and vertically oriented nanotube array of titanium dioxide films were fabricated via the anodization of Ti foil in formamide electrolytes containing NH(4)F at room temperature followed by sensitization of the electrodes with bR. The stability of bR on the TiO(2) surface was found to depend on the pretreatment process of the TiO(2) films. Our results demonstrate the opportunity to fabricate fairly stable bR/TiO(2) hybrid electrodes that can be used as photoanodes for photoelectrochemical water splitting. Under AM 1.5 illumination (100 mW/cm(2)), the hybrid electrodes achieved a photocurrent density of 0.65 mA/cm(2) which is a similar to 50\% increase over that measured for pure TiO(2) nanotubes (0.43 mA/cm(2)) fabricated and tested under the same conditions. In the presence of a redox electrolyte, the photocurrent increased to 0.87 mA/cm(2). To the best of our knowledge, this is the first report on the use of bR/TiO(2) hybrid electrodes in photoelectrochemical water oxidation cells. We believe the proton pumping property of bR can be used in a variety of applications, especially those related to third generation photovoltaic cells.},
	isbn = {1754-5692},
	doi = {10.1039/c1ee01447a},
	author = {Allam, N. K. and Yen, C. W. and Near, R. D. and El-Sayed, Mostafa A}
}
@article {1081,
	title = {Electrochemical Fabrication of Strontium-Doped TiO(2) Nanotube Array Electrodes and Investigation of Their Photoelectrochemical Properties},
	journal = {Journal of Physical Chemistry C},
	volume = {115},
	number = {27},
	year = {2011},
	note = {Hamedani, Hoda A. Allam, Nageh K. Garmestani, Hamid El-Sayed, Mostafa A.},
	month = {Jul},
	pages = {13480-13486},
	abstract = {In recent years, considerable efforts have been made to improve the performance of photoactive nanostructured materials for water-splitting applications. Herein, we report on the fabrication and photoelectrochemical properties of highly ordered Sr-doped TiO(2) nanotube arrays synthesized via a one-step electrochemical anodization technique. Nanotube arrays of Sr-doped TiO(2) were synthesized via anodization of titanium foil in aqueous electrolytes containing NH(4)F and various concentrations of Sr(OH)(2) at different electrolyte pHs. The morphology and quality of the fabricated materials were found to be significantly affected by the pH of the electrolyte as well as the solubility limit of Sr(OH)(2) in the test electrolyte. The photoelectrochemical measurements revealed that Sr doping can significantly improve the photoconversion efficiency of the material. Using Sr-doped TiO(2) nanotube arrays, an electrode photoconversion efficiency of 0.69\% was obtained, which is more than 3 times higher than that of the undoped nanotube arrays (0.2\%) fabricated and tested under the same conditions.},
	isbn = {1932-7447},
	doi = {10.1021/jp201194b},
	author = {Hamedani, H. A. and Allam, N. K. and Garmestani, H. and El-Sayed, Mostafa A}
}
@article {1076,
	title = {Following Charge Separation on the Nanoscale in Cu(2)O-Au Nanoframe Hollow Nanoparticles},
	journal = {Nano Letters},
	volume = {11},
	number = {8},
	year = {2011},
	note = {A. Mahmoud, Mahmoud Qian, Wei El-Sayed, Mostafa A.},
	month = {Aug},
	pages = {3285-3289},
	abstract = {Cu(2)O-Au nanoframes with different nanolayer thicknesses of Cu(2)O were prepared, and their photocatalytic properties in aqueous solutions were studied. Cu(2)O semiconductor excitation leads to electron-hole separation. In aqueous solution, the hole is known to oxidize water to produce hydroxyl radicals whose concentration (and that of the holes) can be monitored by the rate of the degradation of dissolved methylene blue dye. The exciton lifetime is determined by femtosecond techniques and is determined by electron-hole recombination which depends on the rates of a number of competing processes such as, electron or hole transfer to an acceptor such as a gold nanoframe and/or the electron or hole trapping processes at the Cu(2)O-Au nanoframe interface. We measured the exciton lifetime as a function of the average Cu(2)O-Au layer separation. A good correlation was found between the rate of the photocatalytic degradation of methylene blue and the exciton lifetime. The exciton lifetime is found to increase as the Cu(2)O thickness is increased. This leads to an increase in the electron-hole separation time and thus an increase in the hole (and so the hydroxyl radical) concentration leading to an observed enhanced rate of the dye degradation.},
	isbn = {1530-6984},
	doi = {10.1021/nl201642r},
	author = {Mahmoud, M A and Qian, Wei and El-Sayed, Mostafa A}
}
@article {1075,
	title = {Influence of Steam Treatment on Dye-Titania Complex Formation and Photoelectric Conversion Property of Dye-Doped Titania Gel},
	journal = {Journal of Physical Chemistry C},
	volume = {115},
	number = {6},
	year = {2011},
	note = {Nishikiori, Hiromasa Uesugi, Yohei Takami, Shohei Setiawan, RudiAgus Fujii, Tsuneo Qian, Wei El-Sayed, Mostafa A.},
	month = {Feb},
	pages = {2880-2887},
	abstract = {Xanthene dye molecules form a chelate complex with the titanium species on the titania surface in dye-titania systems. The complex formation causes a fast electron injection into the titania conduction band. In this study, simple spectroscopic and photocurrent measurements of the xanthene dye-doped titania gels prepared by the sol-gel method were conducted in order to clarify the influence of a steam treatment on the dye-titania interaction and electron transfer. The photocurrent quantum efficiency of the fluorescein-doped electrode was remarkably increased by the steam treatment compared to that of the untreated electrode consisting of an amorphous titania gel. The photocurrent action spectrum was red-shifted, and the short circuit photocurrent and open circuit voltage values increased with the steam treatment time. The steam treatment promoted the dye-titania complex formation, a negative shift in the conduction band potential of the titania, and the electron injection from the dye to the titania.},
	isbn = {1932-7447},
	doi = {10.1021/jp109958z},
	author = {Nishikiori, H. and Uesugi, Y. and Takami, S. and Setiawan, R. and Fujii, T. and Qian, Wei and El-Sayed, Mostafa A}
}
@article {1084,
	title = {Multimodal plasmon coupling in low symmetry gold nanoparticle pairs detected in surface-enhanced Raman scattering},
	journal = {Applied Physics Letters},
	volume = {98},
	number = {18},
	year = {2011},
	note = {Dreaden, Erik C. Near, Rachel D. Abdallah, Tamer Talaat, M. Hassan El-Sayed, Mostafa A.},
	month = {May},
	abstract = {We report on surface-enhanced Raman scattering of silicon phonon vibrations from arrays of gold nanoprism pairs fabricated by electron beam lithography. We found that resonant excitation of the quadrupolar surface plasmon mode of the nanoprisms increases Raman scattering intensity from the substrate as the distance between the nanoparticle pairs decreases. Finite element modeling and plasmon coupling theory indicate that symmetry is reduced as the nanoparticles approach, resulting in increased dipole-quadrupole coupling. Plasmonic enhancement of the incident and Raman-scattered photons results from the dipolar component of the mixed plasmonic field. This effect is expected to be largest in assemblies/aggregates of nanoparticles. (C) 2011 American Institute of Physics. [doi:10.1063/1.3555429]},
	isbn = {0003-6951},
	doi = {10.1063/1.3555429},
	author = {Dreaden, Erik and Near, R. D. and Abdallah, T. and Talaat, M. H. and El-Sayed, Mostafa A}
}
@article {1083,
	title = {Plasmonic Enhancement of Nonradiative Charge Carrier Relaxation and Proposed Effects from Enhanced Radiative Electronic Processes in Semiconductor-Gold Core-Shell Nanorod Arrays},
	journal = {Journal of Physical Chemistry C},
	volume = {115},
	number = {13},
	year = {2011},
	note = {Dreaden, Erik C. Neretina, Svetlana Qian, Wei El-Sayed, Mostafa A. Hughes, Robert A. Preston, John S. Mascher, Peter},
	month = {Apr},
	pages = {5578-5583},
	abstract = {Plasmonic field enhancement of nonradiative exciton relaxation rates in vertically aligned arrays of high aspect ratio CdTe-Au core-shell nanorods was investigated by transient absorption spectroscopy, computational electromagnetics, and kinetic modeling. Increasing shell thickness in the high aspect ratio nanorods was found to result in dramatic differences in polarization-dependent nonradiative exciton relaxation rates, which we attribute to differing mechanisms of plasmonic field enhancement associated with predominant ground- or excited-state absorption processes. These results are compared with previous investigations of low aspect ratio CdTe-Au core-shell nanorods, and overall conclusions regarding plasmonic enhancement of nonradiative relaxation rates in this system are presented. We propose that when the resonantly coupled dipolar plasmon field of the shell is polarized parallel to the ground-state absorption transition moment of the core, Auger recombination dominates carrier relaxation and slower second-order decay kinetics are observed. When contributions of the resonantly coupled plasmon field are nondipolar or orthogonal to the ground-state absorption transition moment of the core, excited-state absorption processes are believed to dominate and increasingly rapid first-order relaxation kinetics are observed. We find that these processes can vary greatly, depending on shell thickness and the orientation of the array, but are insensitive to aspect ratio. These investigations have significant implications in the design of photovoltaic and optoelectronic devices incorporating anisotropic plasmonic elements.},
	isbn = {1932-7447},
	doi = {10.1021/jp112129k},
	author = {Dreaden, Erik and Neretina, Svetlana and Qian, Wei and El-Sayed, Mostafa A and Hughes, Robert A and Preston, John S and Mascher, Peter}
}
@article {1077,
	title = {Plasmonic Field Effects on the Energy Transfer between Poly(p-phenyleneethynylene) Fluorescent Polymer and Au Nanocages},
	journal = {Journal of Physical Chemistry C},
	volume = {115},
	number = {26},
	year = {2011},
	note = {Mahmoud, M. A. El-Sayed, M. A.},
	month = {Jul},
	pages = {12726-12735},
	abstract = {Colloidal gold nanocages (AuNCs) with a wall length of 60 nm and wall thickness of 6 nm were prepared by the galvanic replacement method. The AuNCs were assembled into monolayers with different percents of surface coverage, using the Langmuir-Blodgett technique. The same technique was used to coat the assembled monolayers of AuNCs with another monolayer of poly(p-phenyleneethynylene) (PPE) fluorescent polymer. The surface plasmon resonance (SPR) spectrum of the AuNCs red-shifts as the percent of AuNCs coverage increases due to growth of the interparticle surface plasmon resonance field coupling as interparticle distance decreases. While after coating the AuNCs array with PPE, the SPR of all the AuNCs monolayers arrays were red-shifted to the same position (693 nm). This unsystematic red-shift behavior is based on the presence of two plasmon fields (inside and outside of AuNCs) and is described by discrete dipole approximation (DDA) simulation. The polymer fluorescence intensity is found to decrease when the polymer is deposited over the AuNCs. This observation is due to the energy transfer between the excited PPE and the AuNCs as well interchain energy transfer. Upon turning on the plasmonic field (exciting the surface plasmon resonance band), it is found that the fluorescence intensity of the polymer increased to a maximum value at AuNCs percent coverage of 10\% and then decreased as the interparticle separation distance decreased. DDA calculations showed that this is consistent with the dependence of the SPR field strength on the interparticle separation. Physically, this is a result of the interplay between the changes in the surface plasmon fields within the cavity of each nanoparticle and their external surface fields as a pair of AuNCs approach one another.},
	isbn = {1932-7447},
	doi = {10.1021/jp2007528},
	author = {Mahmoud, M A and El-Sayed, Mostafa A}
}
@article {1325,
	title = {Plasmonic Imaging of Human Oral Cancer Cell Communities during Programmed Cell Death by Nuclear-Targeting Silver Nanoparticles},
	journal = {Journal of the American Chemical Society},
	volume = {133},
	number = {44},
	year = {2011},
	note = {Times Cited: 13Austin, Lauren A. Kang, Bin Yen, Chun-Wan El-Sayed, Mostafa A.},
	month = {Nov},
	pages = {17594-17597},
	abstract = {Plasmonic nanoparticles (NPs) have become a useful platform in Medicine for potential uses in disease diagnosis and treatment. Recently, it has been reported that plasmonic NPs conjugated to nuclear targeting peptides cause DNA damage and apoptotic populations in cancer cells. In the present work, we utilized the plasmonic scattering property and the ability of nuclear-targeted silver nanoparticles (NLS/RGD-AgNPs) to induce programmed cell death in order to image in real-time the behavior of human oral squamous carcinoma (HSC-3) cell communities during and after the induction of apoptosis. Plasmonic live-cell imaging revealed that HSC-3 cells behave as nonprofessional phagocytes. The induction of apoptosis in some cells led to attraction of and their subsequent engulfment by neighboring cells. Attraction to apoptotic cells resulted in clustering of the cellular community. Live-cell imaging also revealed that,. as the initial,concentration of NLS/RGD-AgNPs. increases, the rate of self killing increases and the degree of attraction and clustering decreases. These results are discussed in terms of the proposed mechanism of cells undergoing programmed cell death.},
	isbn = {0002-7863},
	doi = {10.1021/ja207807t},
	author = {Austin, Lauren and Kang, B. and Yen, C. W. and El-Sayed, M. A.}
}
@article {1082,
	title = {Plasmonic photochemistry and photon confinement to the nanoscale},
	journal = {Journal of Photochemistry and Photobiology a-Chemistry},
	volume = {221},
	number = {2-3},
	year = {2011},
	note = {El-Sayed, Mostafa A.Si},
	month = {Jun},
	pages = {138-142},
	abstract = {This account gives a simple qualitative discussion of the confinement of the motion of electrons to the nanoscale. The mechanism by which gold and silver nanoparticles confine photons to the nanoscale, resulting in both the surface plasmon resonance and strong surface plasmon fields, is mentioned. Examples of different observations and applications of the plasmonic field enhancement of light scattering, absorption, photo-thermal and nonradiative processes studied in our group are summarized. (C) 2011 Elsevier B.V. All rights reserved.},
	isbn = {1010-6030},
	doi = {10.1016/j.jphotochem.2011.05.024},
	author = {El-Sayed, Mostafa A}
}
@article {1079,
	title = {Plasmonic Spheroidal Metal Nanoshells Showing Larger Tunability and Stronger Near Fields Than Their Spherical Counterparts: An Effect of Enhanced Plasmon Coupling},
	journal = {Journal of Physical Chemistry Letters},
	volume = {2},
	number = {5},
	year = {2011},
	note = {Hooshmand, Nasrin Jain, Prashant K. El-Sayed, Mostafa A.},
	month = {Mar},
	pages = {374-378},
	abstract = {Two of the most tunable nanostructure geometries for nanoplas monics include the metal nanoshell structure and the spheroidal geometry. We systematically investigate the effect of combining both geometries within the same nanostructure. Localized surface plasmon resonances (LSPRs) of spheroidal gold nanoshells are simulated as a function of their aspect ratio. The long-axis LSPR mode of a spheroidal nanoshell red shifts with decreasing shell thickness, similar to a spherical nanoshell. A higher aspect ratio spheroidal nanoshell shows a larger fractional LSPR red shift for the same thickness normalized by core dimensions. This is because coupling between the inner and outer surface plasmons of the nanoshell is stronger for the elongated spheroidal geometry as compared to that for the spherical case, increasing in strength with increasing aspect ratio. It is the result of this enhanced plasmon coupling that spheroidal nanoshells of aspect ratio 4 are over two times more tunable than spherical nanoshells. Also, the plasmonic field enhancement is an order of magnitude larger for the spheroidal nanoshells of aspect ratio 4 as compared to spherical nanoshells. These effects observed in the spheroidal nanoshell are analogous to those in a dimer of spheroidal nanopatides.},
	isbn = {1948-7185},
	doi = {10.1021/jz200034j},
	author = {Hooshmand, N. and Jain, Prashant K and El-Sayed, Mostafa A}
}
@article {1088,
	title = {Remote Triggered Release of Doxorubicin in Tumors by Synergistic Application of Thermosensitive Liposomes and Gold Nanorods},
	journal = {Acs Nano},
	volume = {5},
	number = {6},
	year = {2011},
	note = {Agarwal, Abhiruchi Mackey, Megan A. El-Sayed, Mostafa A. Bellamkonda, Ravi V.},
	month = {Jun},
	pages = {4919-4926},
	abstract = {Delivery cif chemotherapeutic agents after encapsulation in nanocarriers such as liposomes diminishes side-effects, as PEGylated nanocarrier pharmacokinetics decrease dosing to healthy tissues and accumulate in tumors due to the enhanced permeability and retention effect. Once in the tumor, however, dosing of the chemotherapeutic to tumor cells is limited potentially by the rate of release from the carriers and the size-constrained, poor diffusivity of nanocarriers in tumor interstitium. Here, we report the design and fabrication of a thermosensitive liposomal nanocarder that maintains its encapsulation stability with a high concentration of doxorubicin payload, thereby minimizing "leak" and attendant toxicity. When used synergistically with PEGylated gold nanorods and near-infrared stimulation, remote triggered release of doxorubicin from thermosensitive liposomes was achieved in a mouse tumor model of human glioblastoma (U87), resulting in a. significant increase in efficacy when compared to nontriggered or nonthermosensitive PEGylated liposomes. This enhancement in efficacy is attributed to increase in tumor-site apoptosis, as was evident from noninvasive apoptosis imaging using Annexin-Vivo 750 probe. This strategy afford; remotely triggered control of tumor dosing of nanocarrier-encapsulated doxorubicin without sacrificing the ability to differentially dose drugs to tumors via the enhanced permeation and retention effect.},
	isbn = {1936-0851},
	doi = {10.1021/nn201010q},
	author = {Agarwal, A. and Mackey, M. A. and El-Sayed, Mostafa A and Bellamkonda, R. V.}
}
@article {1080,
	title = {Self-Standing Crystalline TiO(2) Nanotubes/CNTs Heterojunction Membrane: Synthesis and Characterization},
	journal = {Acs Applied Materials \& Interfaces},
	volume = {3},
	number = {4},
	year = {2011},
	note = {Hesabi, Zohreh R. Allam, Nageh K. Dahmen, Klaus Garmestani, Hamid El-Sayed, Mostafa A.},
	month = {Apr},
	pages = {952-955},
	abstract = {In the present study, we report for the first time synthesis of TiO(2) nanotubes/CNTs heterojunction membrane. Chemical vapor deposition (CVD) of CNTs at 650 degrees C in a mixture of H(2)/He atmosphere led to in situ detachment of the anodically fabricated TiO(2) nanotube layers from the Ti substrate underneath. Morphological and structural evolution of TiO(2) nanotubes after CNTs deposition were investigated by field- emission scanning electron microscopy (FESEM), glancing angle X-ray diffraction (GAXRD), and X-ray photoelectron spectroscopy (XPS) analyses.},
	isbn = {1944-8244},
	doi = {10.1021/am200124p},
	author = {Hesabi, Z. R. and Allam, N. K. and Dahmen, K. and Garmestani, H. and El-Sayed, Mostafa A}
}
@article {1074,
	title = {Tailoring Plasmonic and Electrostatic Field Effects To Maximize Solar Energy Conversion by Bacteriorhodopsin, the Other Natural Photosynthetic System},
	journal = {Nano Letters},
	volume = {11},
	number = {9},
	year = {2011},
	note = {Yen, Chun-Wan Hayden, Steven C. Dreaden, Erik C. Szymanski, Paul El-Sayed, Mostafa A.},
	month = {Sep},
	pages = {3821-3826},
	abstract = {We have explored the plasmonic field enhancement of current production from bacteriorhodopsin (bR) by maximizing the blue light effect, where the influx of blue photons absorbed by the long-lived M intermediate drastically shortens the time scale of the bR photocycle, leading to current enhancement. To this end, we used three approaches in our solution-based cell: proton selective Nafion membrane. (2) We maximized the plasmonic surface (1) We improved the charge carrier separation in solution through the use of a field effects by selecting the capping polymer with minimum surface field screening and best nanopartide stability. (3) We selected the plasmonic nanoparticle with the strongest plasmonic field whose surface plasmon resonance has the largest spectral overlap with the blue light absorbing M-intermediate. Theoretical models are used to explain experimental results, which show a 40 nm cuboidal nanoparticle capped with 55k PVP polymer to give the best photocurrent enhancement. Enhanced by this particle, bR in our Nafion membrane solution cell gave a photocurrent of 0.21 mu A/cm(3), which is 5000 times larger than the published results for thin film bR electrochemical cells even with an applied bias. Additional possible enhancements are proposed.},
	isbn = {1530-6984},
	doi = {10.1021/nl2018959},
	author = {Yen, C. W. and Hayden, S. C. and Dreaden, Erik and Szymanski, P. and El-Sayed, Mostafa A}
}
@article {1078,
	title = {Time Dependence and Signs of the Shift of the Surface Plasmon Resonance Frequency in Nanocages Elucidate the Nanocatalysis Mechanism in Hollow Nanoparticles},
	journal = {Nano Letters},
	volume = {11},
	number = {3},
	year = {2011},
	note = {Mahmoud, M. A. El-Sayed, M. A.},
	month = {Mar},
	pages = {946-953},
	abstract = {Surface plasmon resonance (SPR) wavelength of plasmonic nanopartides is sensitive to changes in the dielectric function of its exposed surface to the medium. Gold nanocages (AuNCs) have two surfaces (inner and outer) and thus two plasmon fields., When the dielectric of the medium changes around the outer surface only, the SPR shifts to different extent from that observed when the dielectric constant of the medium changes around both surfaces. This property of plasmonic AuNCs was used to elucidate the mechanism of the catalytic reduction of 4-nitro to 4-amino phenol, whether it is occurring within the cavity or on the exterior surface of the nanocages. For this purpose two types of nanocages were prepared, one with two plasmonic surfaces and the other with Au/Pt shell-shell nanocages, where only the external surface is plasmonic as gold is outside and Pt is inside. By following the time dependence of the plasmonic band shift resulting from the addition of the reactants and comparing the reaction kinetic parameters for two types of nanocages with those of the pure single metallic nanocages, it was concluded that the catalysis is taking place within the cavity in both types of hollow nanopartides.},
	isbn = {1530-6984},
	doi = {10.1021/nl103265s},
	author = {Mahmoud, M A and El-Sayed, Mostafa A}
}
@article {1087,
	title = {Vertically Oriented Ti-Pd Mixed Oxynitride Nanotube Arrays for Enhanced Photoelectrochemical Water Splitting},
	journal = {Acs Nano},
	volume = {5},
	number = {6},
	year = {2011},
	note = {Allam, Nageh K. Poncheri, Adam J. El-Sayed, Mostafa A.},
	month = {Jun},
	pages = {5056-5066},
	abstract = {In recent years, considerable efforts have been made to design and discover photoactive nanostructured materials that can be used as anodes in water photoelectrolysis cells. Herein, we report on the growth of a novel photoanode material composed of self-ordered, vertically oriented nanotube arrays of titanium palladium mixed oxynitride films via anodization of Ti-Pd alloy in an electrolyte solution of formamide containing NH(4)F at room temperature, followed by annealing in an ammonia atmosphere. The nanostructure topology was found to depend on both the anodization time and the applied voltage. Our results demonstrate the ability to grow mixed oxynitride nanotube array films that are several micrometers thick. The Ti-Pd oxynitride nanotube array films were utilized In solar-spectrum water photoelectrolysis, demonstrating a photocurrent density of 1.9 mA/cm(2) and a similar to 5-fold increase in the photoconversion efficiency under AM 1.5 illumination (100 mW/cm(2), 1.0 M KOH) compared to pure TiO(2) nanotubes fabricated and tested under the same conditions; The obtained efficiency is among the highest reported values for a TiO(2) nanotube-based photoelectrochemical cell. This enhancement in the photoconversion efficiency is related to the synergistic effects of Pd alloying, nitrogen doping, and the unique structural properties of the fabricated nanotube arrays.},
	isbn = {1936-0851},
	doi = {10.1021/nn201136t},
	author = {Allam, N. K. and Poncheri, A. J. and El-Sayed, Mostafa A}
}
@inbook {809,
	title = {Applications of gold nanorods for cancer imaging and photothermal therapy},
	booktitle = {Methods in Molecular Biology},
	volume = {624},
	year = {2010},
	pages = {343-357},
	publisher = {Springer},
	organization = {Springer},
	chapter = {23},
	abstract = {This chapter describes the application of gold nanorods in biomedical imaging and photothermal therapy.  The photothermal properties of gold nanorods are summarized and the synthesis as well as antibody conjugation of gold nanorods is outlined.  Biomedical applications of gold nanorods include cancer imaging using their enhanced scattering properties and photothermal therapy using their enhanced nonradioactive photothermal property.},
	keywords = {cancer, gold nanorods, imaging, photothermal therapy},
	isbn = {1064-3745},
	doi = {10.1007/978-1-60761-609-2_23},
	url = {http://dx.doi.org/10.1007/978-1-60761-609-2_23},
	author = {Huang, Xiaohua and El Sayed, I.H. and El-Sayed, Mostafa A and Grobmyer, SR}
}
@article {1103,
	title = {Bacteriorhodopsin O-state Photocycle Kinetics: A Surfactant Study},
	journal = {Photochemistry and Photobiology},
	volume = {86},
	number = {1},
	year = {2010},
	note = {Chu, Li-Kang El-Sayed, Mostafa A.},
	month = {Jan-Feb},
	pages = {70-76},
	abstract = {The spectroscopy and dynamics of interaction between the O intermediate of bacteriorhodopsin (bR) and several surfactants (cetrimonium bromide [CTAB], sodium dodecyl sulfate [SDS] and diethylene glycol mono-n-hexyl ether [C6E2]) were investigated using steady-state UV-VIS spectrometry, circular dichroism spectroscopy and time-resolved absorption techniques. The steady-state spectral results show that bR can retain its trimeric state without severe damage in the molar concentration ratio of C6E2/bR ranging up to 4000. Time-resolved observations indicate that the rise and decay rates and transient populations of the O state can be increased in the presence of nonionic surfactant C6E2; however, these studies indicate the opposite phenomenon in the presence of the ionic surfactants CTAB and SDS. The observed 40\% enhancement in the transient population of the O intermediate state that results from treatment of C6E2 is proposed to result from an expanding bR structure, which leads to more effective proton pumping efficiency in the photosynthetic system of bR.},
	isbn = {0031-8655},
	doi = {10.1111/j.1751-1097.2009.00629.x},
	author = {Chu, L. K. and El-Sayed, Mostafa A}
}
@article {1101,
	title = {Bacteriorhodopsin-based photo-electrochemical cell},
	journal = {Biosensors \& Bioelectronics},
	volume = {26},
	number = {2},
	year = {2010},
	note = {Chu, Li-Kang Yen, Chun-Wan El-Sayed, Mostafa A.},
	month = {Oct},
	pages = {620-626},
	abstract = {A simple solution-based electrochemical cell has been constructed and successfully employed in the detection of the photoelectric response upon photoexcitation of bacteriorhodopsin (bR) without external bias. Commercially-available indium tin oxide (ITO) glasses served as the optical windows and electrodes. Small amounts of bR suspensions (similar to 100 mu L) were utilized as the photovoltaic medium to generate the proton gradient between two half-cells separated by a molecular porous membrane. Continuous broadband visible light (lambda >380 nm) and a short-pulse 532-nm laser were employed for the photoexcitation of bR. Upon the modulated cw broadband irradiation, an instantaneous rise and decay of the current was observed. Our observations of the pH-dependent photocurrent are consistent with previous reports in a bR thin film configuration, which also showed a polarity inversion at pH 5-6. This is due to the change of the priority of the proton release and proton uptake in the photocycle of bR. Studies on the ionic strength effect were also carried out at different KC1 concentrations, which resulted in the acceleration of the rise and decay of the photoelectric response. This was accompanied by a decrease in the stationary photocurrent at higher KC1 concentrations in the broadband excitation experiments. The solution-based electrochemical cell uses aqueous medium, which is required for the completion of the bR proton pumping function. Due to the generation of the stationary current, it is advantageous to convert solar energy into electricity without the need of film-based photovoltaic devices with external bias. (C) 2010 Elsevier B.V. All rights reserved.},
	isbn = {0956-5663},
	doi = {10.1016/j.bios.2010.07.013},
	author = {Chu, L. K. and Yen, C. W. and El-Sayed, Mostafa A}
}
@article {1097,
	title = {Comparative study of photothermolysis of cancer cells with nuclear-targeted or cytoplasm-targeted gold nanospheres: continuous wave or pulsed lasers},
	journal = {Journal of Biomedical Optics},
	volume = {15},
	number = {5},
	year = {2010},
	note = {Huang, Xiaohua Kang, Bin Qian, Wei Mackey, Megan A. Chen, Po C. Oyelere, Adegboyega K. El-Sayed, Ivan H. El-Sayed, Mostafa A.},
	month = {Sep-Oct},
	abstract = {We conduct a comparative study on the efficiency and cell death pathways of continuous wave (cw) and nanosecond pulsed laser photothermal cancer therapy using gold nanospheres delivered to either the cytoplasm or nucleus of cancer cells. Cytoplasm localization is achieved using arginine-glycine-aspartate peptide modified gold nanospheres, which target integrin receptors on the cell surface and are subsequently internalized by the cells. Nuclear delivery is achieved by conjugating the gold nanospheres with nuclear localization sequence peptides originating from the simian virus. Photothermal experiments show that cell death can be induced with a single pulse of a nanosecond laser more efficiently than with a cw laser. When the cw laser is applied, gold nanospheres localized in the cytoplasm are more effective in inducing cell destruction than gold nanospheres localized at the nucleus. The opposite effect is observed when the nanosecond pulsed laser is used, suggesting that plasmonic field enhancement of the nonlinear absorption processes occurs at high localization of gold nanospheres at the nucleus. Cell death pathways are further investigated via a standard apoptosis kit to show that the cell death mechanisms depend on the type of laser used. While the cw laser induces cell death via apoptosis, the nanosecond pulsed laser leads to cell necrosis. These studies add mechanistic insight to gold nanoparticle-based photothermal therapy of cancer. (c) 2010 Society of Photo-Optical Instrumentation Engineers. [DOI: 10.1117/1.3486538]},
	isbn = {1083-3668},
	doi = {10.1117/1.3486538},
	author = {Huang, Xiaohua and Kang, Bin and Qian, Wei and Mackey, M. A. and Chen, P. C. and Oyelere, A. K. and El Sayed, I.H. and El-Sayed, Mostafa A}
}
@article {810,
	title = {Dark-field light scattering imaging of living cancer cell component from birth through division using bioconjugated gold nanoprobes},
	journal = {Journal of Biomedical Optics},
	volume = {15},
	year = {2010},
	pages = {046025},
	abstract = {Novel methods and technologies that could extend and complement the capabilities of the prevailing fluorescence microscope in following the cell cycle under different perturbations are highly desirable in the area of biological and biomedical imaging. We report a newly designed instrument for long-term light scattering live cell imaging based on integrating a homebuilt environmental cell incubation minichamber and an angled dark-field illumination system into a conventional inverted light microscope. Peptide-conjugated gold nanoparticles that are selectively delivered to either the cytoplasmic or nuclear region of the cell are used as light scattering contrast agents. The new system enables us to carry out continuous and intermittence-free dark-field live cell imaging over several tens of hours. A variety of applications of this imaging system are demonstrated, such as monitoring the nuclear uptake of peptide-conjugated gold nanoparticles, tracking the full cycle of cancer cells from birth to division, following the chromosome dynamics during cell mitosis, and observing the intracellular distribution of gold nanoparticles after cell division. We also discuss the overall effect of nuclear targeting gold nanoparticles on the cell viability of parent and daughter cells.},
	doi = {10.1117/1.3477179},
	url = {http://dx.doi.org/10.1117/1.3477179},
	author = {Qian, Wei and Huang, Xiaohua and Kang, Bin and El-Sayed, Mostafa A}
}
@article {1104,
	title = {Delivery of molecules into cells using carbon nanoparticles activated by femtosecond laser pulses},
	journal = {Nature Nanotechnology},
	volume = {5},
	number = {8},
	year = {2010},
	note = {Chakravarty, Prerona Qian, Wei El-Sayed, Mostafa A. Prausnitz, Mark R.},
	month = {Aug},
	pages = {607-611},
	abstract = {A major barrier to drug and gene delivery is crossing the cell{\textquoteright}s plasma membrane. Physical forces applied to cells via electroporation(1), ultrasound(2) and laser irradiation(3-6) generate nanoscale holes in the plasma membrane for direct delivery of drugs into the cytoplasm. Inspired by previous work showing that laser excitation of carbon nanoparticles can drive the carbon-steam reaction to generate highly controlled shock waves(7-10), we show that carbon black nanoparticles activated by femtosecond laser pulses can facilitate the delivery of small molecules, proteins and DNA into two types of cells. Our initial results suggest that interaction between the laser energy and carbon black nanoparticles may generate photo-acoustic forces by chemical reaction to create transient holes in the membrane for intracellular delivery.},
	isbn = {1748-3387},
	doi = {10.1038/nnano.2010.126},
	author = {Chakravarty, P. and Qian, Wei and El-Sayed, Mostafa A and Prausnitz, M. R.}
}
@article {1106,
	title = {Enhanced Photoassisted Water Electrolysis Using Vertically Oriented Anodically Fabricated Ti-Nb-Zr-O Mixed Oxide Nanotube Arrays},
	journal = {Acs Nano},
	volume = {4},
	number = {10},
	year = {2010},
	note = {Allam, Nageh K. Alamgir, Faisal El-Sayed, Mostafa A.},
	month = {Oct},
	pages = {5819-5826},
	abstract = {Self-ordered, highly oriented arrays of titanium-niobium-zirconium mixed oxide nanotube films were fabricated by the anodization of Ti(35)Nb(5)Zr alloy in aqueous and formamide electrolytes containing NH(4)F at room temperature. The nanostructure topology was found to depend on the nature of the electrolyte and the applied voltage. Our results demonstrate the possibility to grow mixed oxide nanotube array films possessing several-micrometer-thick layers by a simple and straightforward electrochemical route. The fabricated Ti-Nb-Zr-O nanotubes showed a similar to 17.5\% increase in the photoelectrochemical water oxidation efficiency as compared to that measured for pure TiO(2) nanotubes under UV illumination (100 mW/cm(2), 320-400 nm, 1 M KOH). This enhancement could be related to a combination of the effect of the thin wall of the fabricated Ti-Nb-Zr-O nanotubes (10 +/- 2 nm) and the formation of Zr oxide and Nb oxide layers on the nanotube surface, which seems to slow down the electron-hole recombination in a way similar to that reported for Gratzel solar cells.},
	isbn = {1936-0851},
	doi = {10.1021/nn101678n},
	author = {Allam, N. K. and Alamgir, F. and El-Sayed, Mostafa A}
}
@article {1092,
	title = {Experimental Evidence For The Nanocage Effect In Catalysis With Hollow Nanoparticles},
	journal = {Nano Letters},
	volume = {10},
	number = {9},
	year = {2010},
	note = {Mahmoud, M. A. Saira, F. El-Sayed, M. A.},
	month = {Sep},
	pages = {3764-3769},
	abstract = {Five different hollow cubic nanoparticles with wall length of 75 nm Were synthesized from platinum and/or palladium elements. The five nanocatalysts are pure platinum nanocages (PtNCs), pure palladium :nanocages (PdNCs), Pt/Pd hollow shell-shell nanocages (NCs) (where Pd is defined as the inner shell around the cavity) Pd/Pt shell-shell NCs, and Pt-Pd alloy NCs. These are used to catalyze the reduction of 4-nitrophenol with sodium borohydride. The kinetic parameters (rate constants, activation energies, frequency factors, and entropies of activation) of each shell/shell NCs are found to be comparable to that of pure metal NCs made of the same metal coating the cavity in the shell-shell NCs. These results strongly Suggest that the catalytic reaction takes place inside the cavity of the hollow nanoparticles. Because of the nanoreactor confinement effect of the hollow nanocatalysts, the frequency factors obtained from the Arrhenius plots are found to be the highest ever reported for this reduction reaction. This is the reason for enhanced rate of this reaction inside the cavity. The importance of mechanism of the homogeneous and the heterogeneous nanocatalytic reactions occurring on the external surface of a solid nanoparticle are contrasted with those occurring on the nanocavity surface.},
	isbn = {1530-6984},
	doi = {10.1021/nl102497u},
	author = {Mahmoud, M A and Saira, F. and El-Sayed, Mostafa A}
}
@inbook {816,
	title = {Fluorescent Quenching Gold Nanoparticles: Potential Biomedical Applications},
	booktitle = {Metal Enhanced Fluorescence},
	year = {2010},
	month = {06/2010},
	pages = {573-599},
	publisher = {Wiley Online Library},
	organization = {Wiley Online Library},
	chapter = {20},
	keywords = {biomedical applications, fluorescent quenching, gold nanoparticles, Raman spectroscopy, surface plasmon resonance},
	doi = {10.1002/9780470642795.ch20},
	url = {http://dx.doi.org/10.1002/9780470642795.ch20},
	author = {Huang, Xiaohua and El Sayed, I.H. and El-Sayed, Mostafa A}
}
@article {1094,
	title = {Gold Nanoframes: Very High Surface Plasmon Fields and Excellent Near-Infrared Sensors},
	journal = {Journal of the American Chemical Society},
	volume = {132},
	number = {36},
	year = {2010},
	note = {Mahmoud, Mahmoud A. El-Sayed, Mostafa A.},
	month = {Sep},
	pages = {12704-12710},
	abstract = {The sensing efficiency or factor of noble metal nanoparticles is defined as the wavelength shift of the surface plasmon resonance extinction peak position per unit change in the refractive index of the surrounding medium. The sensitivity of different shapes and sizes of gold nanoparticles has been studied by many investigators and found to depend on the plasmon field strength. As a result, the sensitivity factors were found to be larger for hollow nanoparticles than for solid ones of comparable dimensions. This is due to the strong plasmonic fields resulting from the coupling between the external and internal surface plasmon fields in the hollow nanoparticles. In the present paper, the sensitivity factors of a large number of gold nanoframes of different size and wall thickness have been determined by experimental and theoretical computation (using the discrete dipole approximation method). The dependence of the sensitivity factors and the plasmon field strength on the wall thickness and the size of the nanoframes has been determined and is discussed. The sensitivity factors are found to increase linearly with the aspect ratio (wall length/wall thickness) of the nanoframes and are especially sensitive to a decrease in the wall thickness. In comparison with other plasmonic nanoparticles, it is found that nanoframes have sensitivity factors that are 12, 7, and 3 times higher than those of gold nanospheres, gold nanocubes, and gold nanorods, respectively, as well as more than several hundred units higher than those of comparable-size gold nanocages.},
	isbn = {0002-7863},
	doi = {10.1021/ja104532z},
	author = {Mahmoud, M A and El-Sayed, Mostafa A}
}
@article {1102,
	title = {Kinetics of the M-Intermediate in the Photocycle of Bacteriorhodopsin upon Chemical Modification with Surfactants},
	journal = {Photochemistry and Photobiology},
	volume = {86},
	number = {2},
	year = {2010},
	note = {Chu, Li-Kang El-Sayed, Mostafa A.},
	month = {Mar-Apr},
	pages = {316-323},
	abstract = {The spectroscopic and kinetic studies of the interaction between bacteriorhodopsin in the M-intermediate and several surfactants (cetyl trimethyl ammonium bromide, dodecyl trimethyl ammonium bromide, diethylene glycol mono-n-hexyl ether, ethylene glycol mono-n-hexyl ether, sodium 1-decanesulfonate and sodium 1-heptanesulfonate) have been investigated using steady-state UV-VIS spectrometry and time-resolved absorption techniques. The steady-state spectral results show that bR retains its trimeric state. Time-resolved observations indicate that the rate of deprotonation of the protonated Schiff base increases in the presence of the cationic surfactants, whereas insignificant changes are observed in the neutral or anionic surfactants. The rate of the reprotonation of the Schiff base in the transition M -> N is accelerated in anionic and neutral surfactants, but is decelerated in the presence of the cationic surfactants. Surfactants with a longer hydrocarbon tail have a greater effect on the kinetics when compared with surfactants having shorter hydrocarbon tails. The opposite effect is observed when the hydrophilic head of the surfactants contains opposite charges. These distinct kinetics are discussed in terms of the difference in the modified surface hydrophilicity of the bR and the possible protein configurational changes upon surfactant treatments.},
	isbn = {0031-8655},
	doi = {10.1111/j.1751-1097.2009.00666.x},
	author = {Chu, L. K. and El-Sayed, Mostafa A}
}
@article {1100,
	title = {On the Mechanism of the Plasmonic Field Enhancement of the Solar-to-Electric Energy Conversion by the Other Photosynthetic System in Nature (Bacteriorhodopsin): Kinetic and Spectroscopic Study},
	journal = {Journal of Physical Chemistry C},
	volume = {114},
	number = {36},
	year = {2010},
	note = {Chu, Li-Kang Yen, Chun-Wan El-Sayed, Mostafa A.},
	month = {Sep},
	pages = {15358-15363},
	abstract = {We have recently reported Ag nanoparticles (AgNPs) plasmonic field enhancement of the Bacteriorhodopsin (bR) photocurrent observed during its proton pump photocycle in solution. We proposed a mechanism based on the plasmonic field enhancement of the blue light effect which bypasses the slow part of the photocycle and increases the rate of proton production and thus the observed photocurrent. In this present work, we studied the AgNPs plasmonic field effect on the spectroscopy and kinetics of the bR proton pumping photocycle. We examined the blue light effect on both the recovery rate of bR and the decay rate of the M intermediate by using 532-nm short-pulsed laser excitation of bR in the presence of AgNPs and continuous-wave blue light exposure. Our observation showed that the recovery of bR and the decay of the M intermediate are both greatly accelerated in the presence of both AgNPs and blue light simultaneously. This gives support for the proposed mechanism of the enhanced proton current in the presence of AgNPs with a plasmon band in the blue region. It was found experimentally that the 40 nm-AgNPs enhancement of the blue light effect on the decay rate is around 400x larger than that of 8 nm-AgNPs. This is found to be in agreement with the known dependence of the plasmonic field on size and the overlap of the plasmonic extinction band with the absorption band of the M intermediates.},
	isbn = {1932-7447},
	doi = {10.1021/jp105468x},
	author = {Chu, L. K. and Yen, C. W. and El-Sayed, Mostafa A}
}
@article {1105,
	title = {Photoelectrochemical Water Oxidation Characteristics of Anodically Fabricated TiO(2) Nanotube Arrays: Structural and Optical Properties},
	journal = {Journal of Physical Chemistry C},
	volume = {114},
	number = {27},
	year = {2010},
	note = {Allam, Nageh K. El-Sayed, Mostafa A.},
	month = {Jul},
	pages = {12024-12029},
	abstract = {There are currently immense needs to optimize low-cost materials, such as TiO(2), so they can efficiently split water photoelectrochemically into hydrogen and oxygen, thus providing a clean energy fuel. To this end, the nature of the crystalline phase and the dimension of the photocatalyst are of crucial significance. In this study, films of 7 mu m long titania nanotube arrays were fabricated via anodization of titanium foil in formamide electrolytes containing NH(4)F and H(3)PO(4). Upon annealing the as-anodized nanotubes, the anatase-to-rutile phase transformation was found to start at 550 degrees C, which is about 120 degrees C above the temperature observed for the 500 nm long nanotube films, with the nanotube films remaining stable up to 580 degrees C. Analysis of the variation of crystallite size with annealing temperature along with XPS analysis of the films was used to investigate the reason behind this observation. UV-vis measurements showed that the absorption edges of the annealed samples were red shifted from that of the as-anodized sample. The stabilization of the anatase phase up to 550 degrees C, while keeping the tubular structure in place, is very significant as anatase is the most photoactive polymorph of titania. Besides, the 7 mu m long nanotubular structure provides a large surface medium for light utilization through scattering. Used as photoanodes to photoelectrochemically split water, the 580 degrees C crystallized nanotube arrays showed a three-electrode photoconversion efficiency of 10\% under UV illumination (100 mW/cm(2), 320-400 nm, 1 M KOH).},
	isbn = {1932-7447},
	doi = {10.1021/jp1037014},
	author = {Allam, N. K. and El-Sayed, Mostafa A}
}
@article {1095,
	title = {Plasmonic coupling in noble metal nanostructures},
	journal = {Chemical Physics Letters},
	volume = {487},
	number = {4-6},
	year = {2010},
	note = {Jain, Prashant K. El-Sayed, Mostafa A.},
	month = {Mar},
	pages = {153-164},
	abstract = {Noble metal nanostructures display unique and strongly enhanced optical properties due to the phenomenon of localized surface plasmon resonance (LSPR). In assemblies or complex noble metal nanostructures, individual plasmon oscillations on proximal particles can couple via their near-field interaction, resulting in coupled plasmon resonance modes, quite akin to excitonic coupling in molecular aggregates or orbital hybridization in molecules. In this frontier Letter we discuss how the coupling of plasmon modes in certain nanostructure geometries (such as nanoparticle dimers and nanoshells) allows systematic tuning of the optical resonance, and also the confinement and enhancement of the near-field, making possible improved refractive-index sensing and field-enhanced spectroscopy and photochemistry. We discuss the polarization, orientation, and distance-dependence of this near-field coupling especially the universal size-scaling of the plasmon coupling interaction. In addition to radiative properties, we also discuss the effect of inter-particle coupling on the non-radiative electron relaxation in noble metal nanostructures. (C) 2010 Elsevier B.V. All rights reserved.},
	isbn = {0009-2614},
	doi = {10.1016/j.cplett.2010.01.062},
	author = {Jain, Prashant K and El-Sayed, Mostafa A}
}
@article {1089,
	title = {Plasmonic Field Enhancement of the Bacteriorhodopsin Photocurrent during Its Proton Pump Photocycle},
	journal = {Journal of the American Chemical Society},
	volume = {132},
	number = {21},
	year = {2010},
	note = {Yen, Chun-Wan Chu, Li-Kang El-Sayed, Mostafa A.},
	month = {Jun},
	pages = {7250-+},
	abstract = {The proton pump photocycle of bacteriorhodopsin (bR) produces photocurrent on a microsecond time scale which is assigned to the deprotonation step forming the M(412) intermediate. The return of the M(412) intermediate to the bR ground state (bR(570)) has two pathways: (1) thermally via multiple intermediates (which takes 15 ms) or (2) by a more rapid and direct process by absorbing blue light (which takes hundreds of nanoseconds). By using nanoparticles (Ag, Ag-Au, and Au NPs) having different surface plasmon resonance extinction spectra, it is found that Ag NPs whose spectrum overlaps best with the M(412) absorption regions enhance the stationary photocurrent 15 times. This large enhancement is proposed to be due to the accelerated photoexcitation rate of the M(412) (in the presence of the plasmon field of the light in this region) as well as short-circuiting of the photocycle, increasing its duty cycles.},
	isbn = {0002-7863},
	doi = {10.1021/ja101301u},
	author = {Yen, C. W. and Chu, L. K. and El-Sayed, Mostafa A}
}
@article {1093,
	title = {Plasmonic Field Enhancement of the Exciton-Exciton Annihilation Process in a Poly(p-phenyleneethynylene) Fluorescent Polymer by Ag Nanocubes},
	journal = {Journal of the American Chemical Society},
	volume = {132},
	number = {8},
	year = {2010},
	note = {Mahmoud, Mahmoud A. Poncheri, Adam J. Phillips, Ronnie L. El-Sayed, Mostafa A.},
	month = {Mar},
	pages = {2633-2641},
	abstract = {Using the Langmuir-Blodgett (LB) technique, a poly(paraphenyleneethynylene) (PPE) fluorescent conjugated polymer was assembled on either a quartz substrate (system I) or on the surface of silver nanocube (AgNC) monolayers (system II). The fluorescence intensity of the polymer was studied in system I as a function of the surface density of the polymer sample when deposited on quartz substrates and in system II on the surface coverage of the underlying AgNC monolayers. In system I, a continual increase in the fluorescence intensity is observed as the surface density of excited polymer is increased. In system II, the fluorescence intensity of the polymer first increased until a threshold surface coverage of AgNC was reached, after which it decreased rapidly with increasing surface coverage in the AgNC monolayer. The exciting light intensity dependence is studied before and after this threshold in system II. The results suggest that one-photon processes were responsible for the increased intensity before the threshold, and two-photon processes were responsible for the rapid decrease in the polymer fluorescence intensity after the threshold. These observations are explained by the increase of the surface plasmon enhancement of the exciting light intensity as the nanoparticle surface coverage is increased. In turn, this increases the polymer absorption rate, which results in a continuous increase in the exciton density and is evident by an increase in the fluorescence intensity. At the threshold, the increased exciton density leads to an increase in the rate of exciton-exciton collisions, which leads to exciton-exciton annihilations. When this phenomenon becomes faster than the rate of fluorescence emission, an intensity decrease is observed. By exploiting the surface plasmon enhancement of absorption processes, we have observed the first exciton-exciton annihilation using a low-intensity Hg-lamp continuous wave source.},
	isbn = {0002-7863},
	doi = {10.1021/ja907657j},
	author = {Mahmoud, M A and Poncheri, A. J. and Phillips, R. L. and El-Sayed, Mostafa A}
}
@article {1091,
	title = {Polystyrene Microspheres: Inactive Supporting Material for Recycling and Recovering Colloidal Nanocatalysts in Solution},
	journal = {Journal of Physical Chemistry Letters},
	volume = {1},
	number = {1},
	year = {2010},
	note = {Mahmoud, M. A. Snyder, B. El-Sayed, M. A.},
	month = {Jan},
	pages = {28-31},
	abstract = {Alumina and silica have been the most commonly, used solid supports in the recovery of colloidal nanocatalysts in solution. In order to avoid possible involvement of the support in the catalytic mechanism, polystyrene microspheres are here demonstrated to be effective and nonreactive supports on which the nanocatalyst can be easily attached by using the swelling and shrinking properties of the polystyrene microspheres. The activation energy of the reduction of 4-nitrophenol with sodium borohydride on platinum nanocubes free in solution is comparable to those on polystyrene microspheres.},
	isbn = {1948-7185},
	doi = {10.1021/jz9000449},
	author = {Mahmoud, M A and Snyder, B. and El-Sayed, Mostafa A}
}
@article {1099,
	title = {Preparation of Cubic Pt Nanoparticles deposited on Alumina and their Application to Propene Hydrogenation},
	journal = {Chemcatchem},
	volume = {2},
	number = {3},
	year = {2010},
	note = {El-Sayed, Mostafa A. Yoo, Jung Whan},
	month = {Mar},
	pages = {268-271},
	isbn = {1867-3880},
	doi = {10.1002/cctc.200900247},
	author = {El-Sayed, Mostafa A and Yoo, J. W.}
}
@article {808,
	title = {A Reexamination of Active and Passive Tumor Targeting by Using Rod-Shaped Gold Nanocrystals and Covalently Conjugated Peptide Ligands},
	journal = {ACS Nano},
	volume = {4},
	year = {2010},
	note = {doi: 10.1021/nn102055s},
	month = {2010},
	pages = {5887 - 5896},
	publisher = {American Chemical Society},
	abstract = {The targeted delivery of nanoparticles to solid tumors is one of the most important and challenging problems in cancer nanomedicine, but the detailed delivery mechanisms and design principles are still not well understood. Here we report quantitative tumor uptake studies for a class of elongated gold nanocrystals (called nanorods) that are covalently conjugated to tumor-targeting peptides. A major advantage in using gold as a ?tracer? is that the accumulated gold in tumors and other organs can be quantitatively determined by elemental mass spectrometry (gold is not a natural element found in animals). Thus, colloidal gold nanorods are stabilized with a layer of polyethylene glycols (PEGs) and are conjugated to three different ligands: (i) a single-chain variable fragment (ScFv) peptide that recognizes the epidermal growth factor receptor (EGFR); (ii) an amino terminal fragment (ATF) peptide that recognizes the urokinase plasminogen activator receptor (uPAR); and (iii) a cyclic RGD peptide that recognizes the av?3 integrin receptor. Quantitative pharmacokinetic and biodistribution data show that these targeting ligands only marginally improve the total gold accumulation in xenograft tumor models in comparison with nontargeted controls, but their use could greatly alter the intracellular and extracellular nanoparticle distributions. When the gold nanorods are administered via intravenous injection, we also find that active molecular targeting of the tumor microenvironments (e.g., fibroblasts, macrophages, and vasculatures) does not significantly influence the tumor nanoparticle uptake. These results suggest that for photothermal cancer therapy, the preferred route of gold nanorod administration is intratumoral injection instead of intravenous injection.The targeted delivery of nanoparticles to solid tumors is one of the most important and challenging problems in cancer nanomedicine, but the detailed delivery mechanisms and design principles are still not well understood. Here we report quantitative tumor uptake studies for a class of elongated gold nanocrystals (called nanorods) that are covalently conjugated to tumor-targeting peptides. A major advantage in using gold as a ?tracer? is that the accumulated gold in tumors and other organs can be quantitatively determined by elemental mass spectrometry (gold is not a natural element found in animals). Thus, colloidal gold nanorods are stabilized with a layer of polyethylene glycols (PEGs) and are conjugated to three different ligands: (i) a single-chain variable fragment (ScFv) peptide that recognizes the epidermal growth factor receptor (EGFR); (ii) an amino terminal fragment (ATF) peptide that recognizes the urokinase plasminogen activator receptor (uPAR); and (iii) a cyclic RGD peptide that recognizes the av?3 integrin receptor. Quantitative pharmacokinetic and biodistribution data show that these targeting ligands only marginally improve the total gold accumulation in xenograft tumor models in comparison with nontargeted controls, but their use could greatly alter the intracellular and extracellular nanoparticle distributions. When the gold nanorods are administered via intravenous injection, we also find that active molecular targeting of the tumor microenvironments (e.g., fibroblasts, macrophages, and vasculatures) does not significantly influence the tumor nanoparticle uptake. These results suggest that for photothermal cancer therapy, the preferred route of gold nanorod administration is intratumoral injection instead of intravenous injection.},
	isbn = {1936-0851},
	url = {http://dx.doi.org/10.1021/nn102055s},
	author = {Huang, Xiaohua and Peng, Xianghong and Wang, Yiqing and Wang, Yuxiang and Shin, Dong M and El-Sayed, Mostafa A and Nie, Shuming}
}
@article {1090,
	title = {Surface Plasmon Fields and Coupling in the Hollow Gold Nanoparticles and Surface-Enhanced Raman Spectroscopy. Theory and Experiment},
	journal = {Journal of Physical Chemistry C},
	volume = {114},
	number = {16},
	year = {2010},
	note = {Mahmoud, M. A. Snyder, B. El-Sayed, M. A.},
	month = {Apr},
	pages = {7436-7443},
	abstract = {Most gold nanoparticles have surface plasmon fields only surrounding their surfaces. Recently, hollow nanoparticles have been studied, such as gold nanocages (AuNC) and gold nanoframes (ALINE). Those particles have two types of surfaces, one facing the outside and the other within the cavity. Their coupling provides a surface field inside the hollow particle and on the outside surface. Using DDA computational method, we have shown that the coupling between these fields gives field intensities and distribution inside and outside the nanoparticles that are sensitive to the thickness (the distance between the two surfaces) as well as the nanoparticle size. For small sizes, the coupling between the fields on the opposite sides of the cage is detected. These effects are detected by following the changes in the experimentally observed surface plasmon resonance spectra of these nanoparticles and the surface-enhanced Raman spectra of adsorbed molecules. The effect of the interaction between the external and internal field as well as the available surface area inside and outside the nanoparticle effects on the Raman-enhancement is detected by comparing the Raman intensities dependence on the interparticle distance with those observed on solid nanocubes surfaces.},
	isbn = {1932-7447},
	doi = {10.1021/jp9109018},
	author = {Mahmoud, M A and Snyder, B. and El-Sayed, Mostafa A}
}
@article {1098,
	title = {TiO(2) Nanotube/CdS Hybrid Electrodes: Extraordinary Enhancement in the Inactivation of Escherichia coli},
	journal = {Journal of the American Chemical Society},
	volume = {132},
	number = {41},
	year = {2010},
	note = {Hayden, Steven C. Allam, Nageh K. El-Sayed, Mostafa A.},
	month = {Oct},
	pages = {14406-14408},
	abstract = {Titanium dioxide nanotubes offer distinct advantages over films of the same material in the production of hydroxyl radicals and subsequent inactivation of Escherichia coli in wastewater. However, their visible light absorption capabilities are limited. Semiconducting nanocrystals of cadmium sulfide have been used to increase the sensitivity of TiO(2) nanotubes to visible light. A small applied potential, using CdS-coated TiO(2) nanotube arrays, allowed for total inactivation of E. call in hitherto record short time.},
	isbn = {0002-7863},
	doi = {10.1021/ja107034z},
	author = {Hayden, S. C. and Allam, N. K. and El-Sayed, Mostafa A}
}
@article {1116,
	title = {Aggregation of Gold Nanoframes Reduces, Rather Than Enhances, SERS Efficiency Due to the Trade-Off of the Inter- and Intraparticle Plasmonic Fields},
	journal = {Nano Letters},
	volume = {9},
	number = {8},
	year = {2009},
	note = {Mahmoud, M. A. El-Sayed, M. A.},
	month = {Aug},
	pages = {3025-3031},
	abstract = {It is usually observed and understood that aggregation of silver and gold solid nanoparticles gives rise to enhanced SERS spectra due to the increased plasmon field between the particles. In the present work, we observed that the increase of aggregation of Langmuir-Blodgett assembled 80 nm gold nanoframe particles reduces the efficiency of the surf ace-enhanced Raman spectra of adsorbed thiophenol molecules. Using discrete dipole approximation simulation of the plasmonic fields of a pair of nanoframes as a function of their interparticle separation, it is found that at large separation the fields inside the cavities are stronger than those outside. As the interpair separation decreases, the gain in the interparticle field does not make up for the loss in the field within the cavities, supporting the observation of the decrease in the SERS intensity with aggregation.},
	isbn = {1530-6984},
	doi = {10.1021/nl901501x},
	author = {Mahmoud, M A and El-Sayed, Mostafa A}
}
@article {1114,
	title = {The Dependence of the Plasmon Field Induced Nonradiative Electronic Relaxation Mechanisms on the Gold Shell Thickness in Vertically Aligned CdTe-Au Core-Shell Nanorods},
	journal = {Nano Letters},
	volume = {9},
	number = {11},
	year = {2009},
	note = {Neretina, Svetlana Dreaden, Erik C. Qian, Wei El-Sayed, Mostafa A. Hughes, Robert A. Preston, John S. Mascher, Peter},
	month = {Nov},
	pages = {3772-3779},
	abstract = {The dependence of the plasmon field enhancement of the nonradiative relaxation rate of the band gap electrons in vertically aligned CdTe-Au core-shell nanorods on the plasmonic gold nanoshell thickness is examined. Increasing the thickness of the gold nanoshell from 15 to 26 nm is found to change the decay curve from being nonexponential and anisotropic to one that is fully exponential and isotropic (i.e., independent of the nanorod orientation with respect to the exciting light polarization direction). Analysis of the kinetics of the possible electronic relaxation enhancement mechanisms is carried out, and DDA simulated properties of the induced plasmonic field of the thin and thick gold nanoshells are determined. On the basis of the conclusions of these treatments and the experimental results, it is concluded that by increasing the nanoshell thickness the relaxation processes evolve from multiple enhancement mechanisms, dominated by highly anisotropic Auger processes, to mechanism(s) involving first-order excited electron ejection process(es). The former is shown to give rise to nonexponential anisotropic decays in the dipolar plasmon field of the thin nanoshell, while the latter exhibits an exponential isotropic decay in the unpolarized plasmonic field of the thick nanoshell.},
	isbn = {1530-6984},
	doi = {10.1021/nl901960w},
	author = {Neretina, Svetlana and Dreaden, Erik and Qian, Wei and El-Sayed, Mostafa A and Hughes, Robert A and Preston, John S and Mascher, Peter}
}
@article {1111,
	title = {Effect of Orientation on Plasmonic Coupling between Gold Nanorods},
	journal = {Acs Nano},
	volume = {3},
	number = {11},
	year = {2009},
	note = {Tabor, Christopher Van Haute, Desiree El-Sayed, Mostafa A.},
	month = {Nov},
	pages = {3670-3678},
	abstract = {Radiative coupling of induced plasmonic fields in metal nanoparticles has drawn increasing attention in the recent literature due to a combination of improved experimental methods to study such phenomena and numerous potential applications, such as plasmonic nanoparticle rulers and plasmonic circuitry. Many groups, including ours, have used a near-exponential fit to express the size scaling of plasmonic coupling. First, we show experimental agreement between previously simulated nanorod coupling and plasmonic coupling in electron beam lithography (EBL) fabricated nanorods using the near-exponential expression. Next, we study the effect of nanoparticle orientation on plasmonic coupling using EBL and DDA simulations. We develop a mathematical relationship that is consistent with our findings and quantitatively describes plasmonic coupling between nanorods as a function of orientation, separation, induced dipole strength, and the dielectric constant of the medium. For applications utilizing plasmonic coupling to become viable with particle shapes that do not have spherical symmetry, such as nanoprisms and nanorods, comparison of the experimental and theoretical results of how particle orientation affects plasmonic coupling is essential.},
	isbn = {1936-0851},
	doi = {10.1021/nn900779f},
	author = {Tabor, C. E. and Van Haute, D. and El-Sayed, Mostafa A}
}
@article {1113,
	title = {Exciton Lifetime Tuning by Changing the Plasmon Field Orientation with Respect to the Exciton Transition Moment Direction: CdTe-Au Core-Shell Nanorods},
	journal = {Nano Letters},
	volume = {9},
	number = {3},
	year = {2009},
	note = {Neretina, Svetlana Qian, Wei Dreaden, Erik C. El-Sayed, Mostafa A. Hughes, Robert A. Preston, John S. Mascher, Peter},
	month = {Mar},
	pages = {1242-1248},
	abstract = {We studied the anisotropy of the influence of plasmonic fields, arising from the optical excitation of a gold nanoshell plasmon absorption at 770 nm, on the lifetime of the bandgap state of the CdTe core in vertically aligned CdTe-Au core-shell nanorods. The previously observed decrease in the lifetime was studied as a function of the tilt angle between the long axis of the nanorod and the electric field polarization direction of the plasmon inducing exciting light. It is observed that the strongest enhancement to the exciton relaxation rate occurs when the two axes are parallel to one another. These results are discussed in terms of the coupling between the exciton transition moment of the CdTe rod and the electric field polarization direction of the gold nanoshell plasmon at 770 nm, which was determined from theoretical modeling based on the discrete dipole approximation.},
	isbn = {1530-6984},
	doi = {10.1021/nl900183m},
	author = {Neretina, Svetlana and Qian, Wei and Dreaden, Erik and El-Sayed, Mostafa A and Hughes, Robert A and Preston, John S and Mascher, Peter}
}
@article {1119,
	title = {Gold Nanoparticles Surface Plasmon Field Effects on the Proton Pump Process of the Bacteriorhodopsin Photosynthesis},
	journal = {Journal of the American Chemical Society},
	volume = {131},
	number = {7},
	year = {2009},
	note = {Biesso, Arianna Qian, Wei Huang, Xiaohua El-Sayed, Mostafa A.},
	month = {Feb},
	pages = {2442-+},
	abstract = {The rate of the proton pump of bacteriorhodopsin photosynthetic system is examined in the presence of a gold nanorod plasmon field. It is found that while the rate of the proton dissociation from the protonated Schiff base is not affected, the rate of its reprotonation increases. These results are qualitatively discussed in terms of several possible mechanisms.},
	isbn = {0002-7863},
	doi = {10.1021/ja8088873},
	author = {Biesso, A. and Qian, Wei and Huang, Xiaohua and El-Sayed, Mostafa A}
}
@article {1117,
	title = {Gold Nanorods: From Synthesis and Properties to Biological and Biomedical Applications},
	journal = {Advanced Materials},
	volume = {21},
	number = {48},
	year = {2009},
	note = {Huang, Xiaohuo Neretina, Svetiana El-Sayed, Mostafa A.},
	month = {Dec},
	pages = {4880-4910},
	abstract = {Noble metal nanoparticles; are capable of confining resonant photons in such a manner as to induce coherent surface plasmon oscillation of their conduction band electrons, a phenomenon leading to two important properties. Firstly, the confinement of the photon to the nanoparticle{\textquoteright}s dimensions leads to a large increase in its electromagnetic field and consequently great enhancement of all the nanoparticle{\textquoteright}s radiative properties, such as absorption and scattering. Moreover, by confining the photon{\textquoteright}s wavelength to the nanoparticle{\textquoteright}s small dimensions, there exists enhanced imaging resolving powers, which extend well below the diffraction limit, a property of considerable importance in potential device applications. Secondly, the strongly absorbed light by the nanoparticles is followed by a rapid dephasing of the coherent electron motion in tandem with an equally rapid energy transfer to the lattice, a process integral to the technologically relevant photothermal properties of plasmonic nanoparticles. Of all the possible nanoparticle shapes, gold nanorods are especially intriguing as they offer strong plasmonic fields while exhibiting excellent tunability and biocompatibility. We begin this review of gold nanorods by summarizing their radiative and nonradiative properties. Their various synthetic methods are then outlined with an emphasis on the seed-mediated chemical growth. In particular, we describe nanorod spontaneous self-assembly, chemically driven assembly, and polymer-based alignment. The final section details current studies aimed at applications in the biological and biomedical fields.},
	isbn = {0935-9648},
	doi = {10.1002/adma.200802789},
	author = {Huang, Xiaohua and Neretina, Svetlana and El-Sayed, Mostafa A}
}
@article {1107,
	title = {Photocatalysis in Gold Nanocage Nanoreactors},
	journal = {Journal of Physical Chemistry A},
	volume = {113},
	number = {16},
	year = {2009},
	note = {Yen, C. W. Mahmoud, M. A. El-Sayed, M. A.},
	month = {Apr},
	pages = {4340-4345},
	abstract = {The photodegradation of methyl orange was found to take place very efficiently using hollow Au nanocages which are known to have remaining Ag on their interior walls which can be oxidized to Ag(2)O. The degradation rate is found to be more efficient than photodegradation reaction using semiconductor nanomaterials, such as TiO(2) and ZnO. The reaction rate is found to increase by increasing the degree of Ag oxidation on the interior wall of the nanocages prior to the reaction and is a function of the nanocavity size and the pore density of the nanocage walls. As the cage size varies, it is found that the photocatalytic rate increases and then decreases with a maximum rate at nanoparticle size of 75 nm with a medium pore density-in the walls. All these results suggest that the catalysis is occurring inside the cavity, whose interior walls are covered with the Ag(2)O catalysts. Similar to the mechanism proposed in the degradation by the other semiconductors, we propose that the photodegradation mechanism involves the formation of the hydroxyl radical resulting from the photoexcitation of the Ag(2)O semiconductor. The observed results on the rate are discussion in terms of (1) the surface area of the inner wall covered with Ag (Ag(2)O), (2) the density and size of the pores in the walls, and (3) the cavity size of the nanoparticles.},
	isbn = {1089-5639},
	doi = {10.1021/jp811014u},
	author = {Yen, C. W. and Mahmoud, M A and El-Sayed, Mostafa A}
}
@article {1108,
	title = {Plasmonic Field Effect on the Hexacyanoferrate (III)-Thiosulfate Electron Transfer Catalytic Reaction on Gold Nanoparticles: Electromagnetic or Thermal?},
	journal = {Journal of Physical Chemistry C},
	volume = {113},
	number = {45},
	year = {2009},
	note = {Yen, Chun-Wan El-Sayed, Mostafa A.},
	month = {Nov},
	pages = {19585-19590},
	abstract = {The rate of the catalytic reaction between hexacyanoferrate (III) and thiosulfate on gold nanoparticles is found to increase when irradiated with light in resonance with surface plasmon absorption of the gold nanoparticles. Turning on the plasmonic field by turning on light at the surface plasmon extinction band wavelength could increase the rate by one of two possible mechanisms. In the first one, the electromagnetic field could chan-e its radiative or nonradiative electron transfer process (Mechanism I). In the other mechanism (Mechanism II), the strongly absorbed light by the gold nanoparticles is rapidly converted from light energy into heat energy that increases the temperature of the medium and increases the reaction rate. In order to determine which mechanism the plasmonic catalytic effect follows, we determined the activation energy of the reaction by heating the reaction solution via two different methods: irradiation at the surface plasmon resonance of the gold catalyst and by direct heating in a thermostat. The two activation energies are found to be the same, suggesting that the plasmonic field effect in this electron transfer reaction is thermally induced.},
	isbn = {1932-7447},
	doi = {10.1021/jp905186g},
	author = {Yen, C. W. and El-Sayed, Mostafa A}
}
@article {1109,
	title = {Rapid Thermal Tuning of Chromophore Structure in Membrane Protein},
	journal = {Journal of Physical Chemistry B},
	volume = {113},
	number = {13},
	year = {2009},
	note = {Wang, Jianping El-Sayed, Mostafa A.},
	month = {Apr},
	pages = {4184-4186},
	abstract = {We show that the configuration and the optical property of the retinal chromophore in bacteriorhodopsin (bR) can be tuned dynamically from the all-trans configuration to the 13-cis by using a nanosecond laser-induced temperature-jump. The rapid bleach in the visible absorption optical density of retinal has an apparent formation time of ca. 170 ns, whereas the relaxation process finishes within tens of ms. The dynamical transition of retinal from the all-trans to 13-cis species is believed to occur as a result of rapid protein conformational change especially in the vicinity of retinal binding site. Our study reveals the intrinsic dynamical aspect of the retinal chromophore with respect to the protein structure.},
	isbn = {1520-6106},
	doi = {10.1021/jp901560m},
	author = {Wang, Jianping and El-Sayed, Mostafa A}
}
@article {1110,
	title = {The sensitivity of the energy band gap to changes in the dimensions of the CdSe quantum rods at room temperature: STM and theoretical studies},
	journal = {Chemical Physics Letters},
	volume = {473},
	number = {4-6},
	year = {2009},
	note = {Talaat, H. Abdallah, T. Mohamed, M. B. Negm, S. El-Sayed, Mostafa A.},
	month = {May},
	pages = {288-292},
	abstract = {The energy band gap of a series of different sizes of CdSe quantum rods have been determined by STM technique at room temperature. The results confirm that the band gap of CdSe quantum rods (QRs) depends mainly on the width (the dimension of the electron confinement) and only slightly on the length as shown previously in the literatures. The experimental data is compared to that calculated using two theoretical models, the effective mass approximation (EMA) and the semi-empirical pseudopotential method (SEPM). The theoretical values for the energy band gap at varying radius are in agreement with the experimental results within 0.08 eV. (c) 2008 Published by Elsevier B.V.},
	isbn = {0009-2614},
	doi = {10.1016/j.cplett.2008.11.025},
	author = {Talaat, M. H. and Abdallah, T. and Mohamed, MB and Negm, S. and El-Sayed, Mostafa A}
}
@article {1115,
	title = {Surface-Enhanced Raman Scattering Enhancement by Aggregated Silver Nanocube Monolayers Assembled by the Langmuir-Blodgett Technique at Different Surface Pressures},
	journal = {Journal of Physical Chemistry C},
	volume = {113},
	number = {14},
	year = {2009},
	note = {Mahmoud, M. A. Tabor, C. E. El-Sayed, M. A.},
	month = {Apr},
	pages = {5493-5501},
	abstract = {The surface-enhanced Raman scattering spectrum of poly(vinyl) pyrrolidone (PVP) molecules capping 50 nm silver nanocubes assembled in a monolayer via the Langmuir-Blodgett (LB) technique is studied at different surface pressures (at different nanoparticle densities). The observed correlation between the intensity of different SERS bands of the PVP with the nanoparticle density and those of the extinction intensity of the localized surface plasmon resonance bands (as a measure of the surface plasmon field) suggests the following: (1) the observed SERS enhancement results mostly from surface fields of the aggregated nanoparticles; and (2) the relative intensities of the different Raman bands are in reasonable agreement with those expected from the electromagnetic mechanism of enhancement. Besides the large surface plasmon field used in the Raman scattering enhancement, the broad SPR band of the aggregated nanocubes provides an additional advantage in the analytical applications of Raman spectroscopy.},
	isbn = {1932-7447},
	doi = {10.1021/jp900648r},
	author = {Mahmoud, M A and Tabor, C. E. and El-Sayed, Mostafa A}
}
@article {1118,
	title = {Tamoxifen-Poly(ethylene glycol)-Thiol Gold Nanoparticle Conjugates: Enhanced Potency and Selective Delivery for Breast Cancer Treatment},
	journal = {Bioconjugate Chemistry},
	volume = {20},
	number = {12},
	year = {2009},
	note = {Dreaden, Erik C. Mwakwari, Sandra C. Sodji, Quaovi H. Oyelere, Adegboyega K. El-Sayed, Mostafa A.},
	month = {Dec},
	pages = {2247-2253},
	abstract = {The breast cancer treatment drug tamoxifen has been widely administered for more than three decades. This small molecule competes with 17 beta-estradiol for binding to estrogen receptor, a hormone receptor upregulated in a majority of breast cancers, Subsequently initiating programmed cell death. We have synthesized a thiol-PEoylated tamoxifen derivative that can be used to selectively target and deliver plasmonic gold nanoparticles to estrogen receptor positive breast cancer cells with tip to 2.7-fold enhanced drug potency in vitro. Optical microscopy/spectroscopy, tirne-dependent dose-response data, and estrogen competition studies indicate that augmented activity is due to increased rates of intracellular tamoxifen transport by nanoparticle endocytosis, rather than by passive diffusion of the free drug. Both ligand- and receptor-dependent intracellular delivery of gold nanoparticles suggest that plasma membrane localized estrogen receptor alpha may facilitate selective uptake and retention of this and other therapeutic nanoparticle conjugates. Combined targeting selectivity and enhanced potency provides opportunities for both multimodal endocrine treatment strategies and adjunctive laser photothermal therapy.},
	isbn = {1043-1802},
	doi = {10.1021/bc9002212},
	author = {Dreaden, Erik and Mwakwari, S. C. and Sodji, Q. H. and Oyelere, A. K. and El-Sayed, Mostafa A}
}
@article {1112,
	title = {On the Use of Plasmonic Nanoparticle Pairs As a Plasmon Ruler: The Dependence of the Near-Field Dipole Plasmon Coupling on Nanoparticle Size and Shape},
	journal = {Journal of Physical Chemistry A},
	volume = {113},
	number = {10},
	year = {2009},
	note = {Tabor, Christopher Murali, Raghunath Mahmoud, Mahmoud El-Sayed, Mostafa A.},
	month = {Mar},
	pages = {1946-1953},
	abstract = {The localized surface plasmon resonance (LSPR) spectral band of a gold or silver nanoparticle is observed to shift as a result of the near-field plasmonic field of another nanoparticle. The dependence of the observed shift on the interparticle distance is used as a ruler in biological systems and gave rise to a plasmonic ruler equation in which the fractional shift in the dipole resonance is found to decrease near exponentially with the interparticle separation in units of the particle size. The exponential decay length constant was observed to be consistent among a small range of nanoparticle sizes, shapes, and types of metal. The equation was derived from the observed results on disks and spherical nanoparticles and confirmed using results on a DNA conjugated nanosphere system. The aim of the present paper is to use electron beam lithography and DDA calculations to examine the constancy of the exponential decay length value in the plasmonic ruler equation on particle size and shape of a number of particles including nanoparticles of different symmetry and orientations. The results suggest that the exponent is almost independent of the size of the nanoparticle but very sensitive to the shape. A discussion of the nanoparticles most suitable for different applications in biological systems and a comparison of the plasmonic ruler with Forster resonance energy transfer (FRET) is mentioned.},
	isbn = {1089-5639},
	doi = {10.1021/jp807904s},
	author = {Tabor, C. E. and Murali, R. and Mahmoud, M A and El-Sayed, Mostafa A}
}
@article {1120,
	title = {Can the observed changes in the size or shape of a colloidal nanocatalyst reveal the nanocatalysis mechanism type: Homogeneous or heterogeneous?},
	journal = {Topics in Catalysis},
	volume = {48},
	number = {1-4},
	year = {2008},
	note = {Narayanan, Radha Tabor, Christopher El-Sayed, Mostafa A.},
	month = {May},
	pages = {60-74},
	abstract = {The surface energy of metallic nanocrystals is relatively high compared to bulk materials due to the metal-metal bond deficiency of the surface atoms. This results in an insufficient chemical valency. In addition, smaller nanoparticles possess a higher degree of curvature, weakening, the bonding of their surface atoms. This is especially true for non-spherical shapes, which are comprised of a large number of sharp corner and edge sites. These atomic sites possess higher surface energies due to the lower number of shared bonds with the nanoparticle, resulting in instability of the surface atoms and rendering them physically unstable and chemically active. In many instances, the constant "bombardment" of these surface atoms by the solvent molecules as well as by the reactant molecules when these nanocrystals are in colloidal solution could lead to surface atom dissolution, both physically and/or chemically. This phenomenon could alter the functionality of the metallic colloidal nanoparticle from supplying catalytically active sites (in heterogeneous catalysis) to serving as a reservoir of catalytically active species to the solution (in homogeneous catalysis). In the latter type, if the atoms of the nanocatalyst appear in the products, the nanoparticle is no longer a catalyst but a reactant. In this review we attempt to answer the question raised in the title by examining our Previous work on the changes in size, shape, and other physical and chemical properties of colloidal transition metal nanoparticles during the nanocatalysis of two fundamentally different and important reactions: (1) the gentle electron-transfer reaction at room temperature involving the reduction of hexacyanoferrate (III) ions with thiosulfate ions and (2) the more harsh Suzuki cross-coupling reaction between phenylboronic acid and iodobenzene that takes place at 100 degrees C for 12 h. Changes in the nanoparticle dimensions were followed with TEM and HRTEM. Raman and FTIR spectroscopies were used to follow the chemical changes. For each change, we will use the above definition to see if the observed change can help us determine whether the catalysis is homogeneous or heterogeneous.},
	isbn = {1022-5528},
	doi = {10.1007/s11244-008-9057-4},
	author = {Narayanan, Radha and Tabor, C. E. and El-Sayed, Mostafa A}
}
@article {1123,
	title = {Comparative study of the assemblies and the resulting plasmon fields of Langmuir-Blodgett assembled monolayers of silver nanocubes and gold nanocages},
	journal = {Journal of Physical Chemistry C},
	volume = {112},
	number = {37},
	year = {2008},
	note = {Mahmoud, M. A. El-Sayed, M. A.},
	month = {Sep},
	pages = {14618-14625},
	abstract = {Silver nanocubes (72 nm) and gold nanocages (75 nm) were assembled by varying the average interstitial particle distances by the Langmuir-Blodgett technique. The shape of the surface pressure-area isotherms for the two types of nanoparticles are discussed in terms of the degree of surface capping of each nanoparticle which depends on the surface quality. Monolayer films formed at different surface pressures were transferred by the vertical dipping method to silicon and glass substrates where their optical spectra and SEM. images were examined. A red-shift of the strong plasmon peak maximum was observed as the average particle distance was decreased. From the SEM images, the morphology as well as the percent area of the substrate surface covered at different pressures was determined. A linear relationship was observed between the percent of covered area and the plasmon peak maximum, the slope of which reflects the average plasmon field felt by the nanoparticles. The increase in the average field with increasing percent covered area is a result of the decrease in the average nanoparticle separation and/or the increase in the number of nanoparticles in each cluster in the distribution formed. The strength of the plasmon field resulting from gold cages is found to be much higher than that from the silver cubes and increases as the gold wall thickness decreases. These results are discussed in terms of the coupling between the two separate fields of the cage wall surfaces.},
	isbn = {1932-7447},
	doi = {10.1021/jp8040499},
	author = {Mahmoud, M A and El-Sayed, Mostafa A}
}
@article {1128,
	title = {Gigahertz optical modulation resulting from coherent lattice oscillations induced by femtosecond laser pumping of 2D photonic crystals of gold-capped polystyrene microspheres},
	journal = {Advanced Materials},
	volume = {20},
	number = {4},
	year = {2008},
	note = {Huang, Wenyu Qian, Wei El-Sayed, Mostafa A.},
	month = {Feb},
	pages = {733-+},
	abstract = {A gigahertz all-optical modulation technique, based on a mechanism in which the modulation of the transmitted light is caused by the coherent oscillation of the phonon modes of gold caps on periodic polystyrene sphere monolayer arrays, is demonstrated. The modulation frequency can be tuned by changing the size of the polystyrene spheres.},
	isbn = {0935-9648},
	doi = {10.1002/adma.200701543},
	author = {Huang, Wenyu and Qian, Wei and El-Sayed, Mostafa A}
}
@article {1133,
	title = {Gold nanoparticle plasmonic field effect on the primary step of the other photosynthetic system in nature, bacteriorhodopsin},
	journal = {Journal of the American Chemical Society},
	volume = {130},
	number = {11},
	year = {2008},
	note = {Biesso, Arianna Qian, Wei El-Sayed, Mostafa A.},
	month = {Mar},
	pages = {3258-+},
	abstract = {In regards to the effect of the surface plasmon field of gold nanospheres on the rate of primary steps leading to retinal photoisomerization in the photosynthesis of bacterirhodopsin (bR), 4 is believed that the light absorption of bR that leads to its retinal isomerization first involves the formation of a highly polar electronic excited state (1460) of the all-trans isomer which strongly polarizes the protein around it. This is followed by its decay to a viibrationally excited 13-cis isomer (J(625)). The effect of plasmonic field of gold nanospheres of different sizes and concentrations is found to slow down the rate of the isomerization of the polar electronic excited-state to the J625 but has no effect on the vibration relaxation of the isomeric state itself. This is consistent with the electrostatic nature of the plasmonic field.},
	isbn = {0002-7863},
	doi = {10.1021/ja7099858},
	author = {Biesso, A. and Qian, Wei and El-Sayed, Mostafa A}
}
@article {1131,
	title = {Gold nanorod assisted near-infrared plasmonic photothermal therapy (PPTT) of squamous cell carcinoma in mice},
	journal = {Cancer Letters},
	volume = {269},
	number = {1},
	year = {2008},
	note = {Dickerson, Erin B. Dreaden, Erik C. Huang, Xiaohua El-Sayed, Ivan H. Chu, Hunghao Pushpanketh, Sujatha McDonald, John F. El-Sayed, Mostafa A.},
	month = {Sep},
	pages = {57-66},
	abstract = {Plasmonic photothermal therapy (PPTT) is a minimally-invasive oncological treatment strategy in which photon energy is selectively administered and converted into heat sufficient to induce cellular hyperthermia. The present work demonstrates the feasibility of in vivo PPTT treatment of deep-tissue malignancies using easily-prepared plasmonic gold nanorods and a small, portable, inexpensive near-infrared (NIR) laser. Dramatic size decreases in squamous cell carcinoma xenografts were observed for direct (P < 0.0001) and intravenous (P < 0.0008) administration of pegylated gold nanorods in nu/nu mice. Inhibition of average tumor growth for both delivery methods was observed over a 13-day period, with resorption of >57\% of the directly-injected tumors and 25\% of the intravenously-treated tumors. Published by Elsevier Ltd.},
	isbn = {0304-3835},
	doi = {10.1016/j.canlet.2008.04.026},
	author = {Dickerson, E. B. and Dreaden, Erik and Huang, Xiaohua and El Sayed, I.H. and Chu, H. H. and Pushpanketh, S. and McDonald, J. F. and El-Sayed, Mostafa A}
}
@article {1122,
	title = {A new catalytically active colloidal platinum nanocatalyst: The multiarmed nanostar single crystal},
	journal = {Journal of the American Chemical Society},
	volume = {130},
	number = {14},
	year = {2008},
	note = {Mahmoud, Mahmoud A. Tabor, Christopher E. El-Sayed, Mostafa A. Ding, Yong Wang, Zhong Lin},
	month = {Apr},
	pages = {4590-+},
	abstract = {Nanocatalysts that possess large amounts of atoms on sharp corners and edges and high indexed sites are known to be more catalytically active. We report here on a novel yet simple method to synthesize in large yields a very active platinum nanocatalyst; the multiarmed nanostar single crystal. We utilize a seed mediated method using tetrahedral nanoparticles that are also synthesized by a new and simple technique. High-resolution TEM shows that the nanostar has many arms, varying from a few to over 30, whereby even the largest ones :re found to have single-crystal structures. This strongly suggests that they are formed by a growth mechanism of the seed crystals and not by the aggregation of seed crystals, which should produce twinning planes. Due to the reduction reaction of ferricyanide by thiosulfate, the nanostars are found to have an activation energy, which is nearly 60\% of that of the tetrahedral seeds themselves, both having the same PVP capping agent. This is undoubtedly due to the multiarms with edges, corners, and the presence of high indexed facets in the nanostar catalyst.},
	isbn = {0002-7863},
	doi = {10.1021/ja710646t},
	author = {Mahmoud, M A and Tabor, C. E. and El-Sayed, Mostafa A and Ding, Y. and Wang, Z.L.}
}
@article {1125,
	title = {Noble Metal Nanoparticle Pairs: Effect of Medium for Enhanced Nanosensing},
	journal = {Nano Letters},
	volume = {8},
	number = {12},
	year = {2008},
	note = {Jain, Prashant K. El-Sayed, Mostafa A.},
	month = {Dec},
	pages = {4347-4352},
	abstract = {In this Letter, we show using both a quasi-static model and discrete dipole approximation simulations of nanoparticle pairs that the surface plasmon resonance shift resulting from the electromagnetic coupling between noble metal nanoparticles increases with an increase in the dielectric constant of the medium. As the particle pair partners approach each other, there is an increase in the rate at which the plasmon resonance shifts in response to a medium refractive index change. Thus, the surface plasmon resonance of a plasmonic nanoparticle pair exhibits higher sensitivity to the environment/medium refractive index as compared to an isolated nanoparticle. The medium sensitivity of the particle pair is shown to increase near exponentially with a decrease in the interparticle separation between the nanoparticles. We therefore propose that enhanced plasmon resonance nanosensing may be achieved by employing coupled particles instead of colloids or arrays of noninteracting particles.},
	isbn = {1530-6984},
	doi = {10.1021/nl8021835},
	author = {Jain, Prashant K and El-Sayed, Mostafa A}
}
@article {1124,
	title = {Noble Metals on the Nanoscale: Optical and Photothermal Properties and Some Applications in Imaging, Sensing, Biology, and Medicine},
	journal = {Accounts of Chemical Research},
	volume = {41},
	number = {12},
	year = {2008},
	note = {Jain, Prashant K. Huang, Xiaohua El-Sayed, Ivan H. El-Sayed, Mostafa A.},
	month = {Dec},
	pages = {1578-1586},
	abstract = {Noble metal nanostructures attract much interest because of their unique properties, including large optical field enhancements resulting in the strong scattering and absorption of light. The enhancement in the optical and photothermal properties of noble metal nanoparticles arises from resonant oscillation of their free electrons in the presence of light, also known as localized surface plasmon resonance (LSPR). The plasmon resonance can either radiate light (Mie scattering), a process that finds great utility in optical and imaging fields, or be rapidly converted to heat (absorption); the latter mechanism of dissipation has opened up applications in several new areas. The ability to integrate metal nanoparticles into biological Systems has had greatest impact in biology and biomedicine. In this Account we discuss the plasmonic properties of gold and silver nanostructures and present examples of how they are being utilized for biodiagnostics, biophysical studies, and medical therapy. For instance, taking advantage of the strong LSPR scattering of gold nanoparticles conjugated with specific targeting molecules allows the mollecule-specific imaging and diagnosis of diseases such as cancer. We emphasize in particular how the unique tunability of the plasmon resonance properties of metal nanopartides through variation of their size, shape, composition, and medium allows chemists to design nanostructures geared for specific bio-applications. We discuss some interesting nanostructure geometries, including nanorods, nanoshells, and nanopartide pairs, that exhibit dramatically enhanced and tunable plasmon resonances, making them highly suitable for bio-applications. Tuning the nanostructure shape (e.g., nanoprisms, nanorods, or nanoshells) is another means of enhancing the sensitivity of the LSPR to the nanopartide environment and, thereby, designing effective biosensing agents. Metal nanopartide pairs or assemblies display distance-dependent plasmon resonances as a result of field coupling. A universal scaling model, relating the plasmon resonance frequency to the interpartide distance in terms of the particle size, becomes potentially useful for measuring nanoscale distances (and their changes) in biological systems. The strong plasmon absorption and photothermal conversion of gold nanoparticles has been exploited in cancer therapy through the selective localized photothermal heating of cancer cells. For nanorods or nanoshells, the LSPR can be tuned to the near-infrared region, making it possible to perform in vivo imaging and therapy. The examples of the applicators of noble metal nanostructures provided herein can be readily generalized to other areas of biology and medicine because plasmonic nanomaterials exhibit great range, versatility, and systematic tunability of their optical attributes.},
	isbn = {0001-4842},
	doi = {10.1021/ar7002804},
	author = {Jain, Prashant K and Huang, Xiaohua and El Sayed, I.H. and El-Sayed, Mostafa A}
}
@article {1129,
	title = {Photothermally excited coherent lattice phonon oscillations in plasmonic nanoparticles},
	journal = {European Physical Journal-Special Topics},
	volume = {153},
	year = {2008},
	note = {Huang, W. El-Sayed, M. A.14th International Conference on Photoacoustic and Photothermal Phenomena/1st US-Egypt Workshop on Photoacoustic and Photothermal PhenomenaJan 07-11, 2007Cairo, EGYPT},
	month = {Jan},
	pages = {325-333},
	abstract = {The photothermal property of (Ag and Au) plasmonic nanoparticles has brought about many important discoveries and applications in nanoscience and nanotechnology. In this review, we briefly summarize a photothermal effect, the coherent phonon oscillation, of plasmonic nanoparticles irradiated with ultrafast laser pulses of low power density. The coherent phonon oscillation is created in the nanoparticle by the ultrafast impulsive photothermal heating. The effects of size, shape, thickness, and interparticle interaction on the period of coherent phonon oscillations are discussed. The detection of the coherent lattice oscillation of metallic nanoparticles provides a powerful tool to characterize the mechanical and structural properties of nanostructures.},
	isbn = {1951-6355},
	doi = {10.1140/epjst/e2008-00456-x},
	author = {Huang, Wenyu and El-Sayed, Mostafa A}
}
@article {811,
	title = {Plasmon Field Effects on the Nonradiative Relaxation of Hot Electrons in an Electronically Quantized System: CdTe-Au Core-Shell Nanowires},
	journal = {Nano Letters},
	volume = {8},
	year = {2008},
	note = {doi: 10.1021/nl801303g},
	month = {2008},
	pages = {2410 - 2418},
	publisher = {American Chemical Society},
	abstract = {The intense electromagnetic fields of plasmonic nanoparticles, resulting from the excitation of their localized surface plasmon oscillations, are known to enhance radiative processes. Their effect on the nonradiative electronic processes, however, is not as well-documented. Here, we report on the enhancement of the nonradiative electronic relaxation rates in CdTe nanowires upon the addition of a thin gold nanoshell, especially at excitation energies overlapping with those of the surface plasmon oscillations. Some possible mechanisms by which localized surface plasmon fields can enhance nonradiative relaxation processes of any quantized electronic excitations are proposed.The intense electromagnetic fields of plasmonic nanoparticles, resulting from the excitation of their localized surface plasmon oscillations, are known to enhance radiative processes. Their effect on the nonradiative electronic processes, however, is not as well-documented. Here, we report on the enhancement of the nonradiative electronic relaxation rates in CdTe nanowires upon the addition of a thin gold nanoshell, especially at excitation energies overlapping with those of the surface plasmon oscillations. Some possible mechanisms by which localized surface plasmon fields can enhance nonradiative relaxation processes of any quantized electronic excitations are proposed.},
	isbn = {1530-6984},
	doi = {10.1021/nl801303g},
	url = {http://dx.doi.org/10.1021/nl801303g},
	author = {Neretina, Svetlana and Qian, Wei and Dreaden, Erik and El-Sayed, Mostafa A and Hughes, Robert A and Preston, John S and Mascher, Peter}
}
@article {1127,
	title = {Plasmonic photothermal therapy (PPTT) using gold nanoparticles},
	journal = {Lasers in Medical Science},
	volume = {23},
	number = {3},
	year = {2008},
	note = {Huang, Xiaohua Jain, Prashant K. El-Sayed, Ivan H. El-Sayed, Mostafa A.},
	month = {Jul},
	pages = {217-228},
	abstract = {The use of lasers, over the past few decades, has emerged to be highly promising for cancer therapy modalities, most commonly the photothermal therapy method, which employs light absorbing dyes for achieving the photothermal damage of tumors, and the photodynamic therapy, which employs chemical photosensitizers that generate singlet oxygen that is capable of tumor destruction. However, recent advances in the field of nanoscience have seen the emergence of noble metal nanostructures with unique photophysical properties, well suited for applications in cancer phototherapy. Noble metal nanoparticles, on account of the phenomenon of surface plasmon resonance, possess strongly enhanced visible and near-infrared light absorption, several orders of magnitude more intense compared to conventional laser phototherapy agents. The use of plasmonic nanoparticles as highly enhanced photoabsorbing agents has thus introduced a much more selective and efficient cancer therapy strategy, viz. plasmonic photothermal therapy (PPTT). The synthetic tunability of the optothermal properties and the bio-targeting abilities of the plasmonic gold nanostructures make the PPTT method furthermore promising. In this review, we discuss the development of the PPTT method with special emphasis on the recent in vitro and in vivo success using gold nanospheres coupled with visible lasers and gold nanorods and silica-gold nanoshells coupled with near-infrared lasers.},
	keywords = {display},
	isbn = {0268-8921},
	doi = {10.1007/s10103-007-0470-x},
	author = {Huang, Xiaohua and Jain, Prashant K and El Sayed, I.H. and El-Sayed, Mostafa A.}
}
@article {1130,
	title = {Pulsed laser photothermal annealing and ablation of plasmonic nanoparticles},
	journal = {European Physical Journal-Special Topics},
	volume = {153},
	year = {2008},
	note = {Huang, W. El-Sayed, M. A.14th International Conference on Photoacoustic and Photothermal Phenomena/1st US-Egypt Workshop on Photoacoustic and Photothermal PhenomenaJan 07-11, 2007Cairo, EGYPT},
	month = {Jan},
	pages = {223-230},
	abstract = {In this review, we briefly summarize the photothermal properties of plasmonic nanoparticles. Several photothermal effects of plasmonic nanoparticles irradiated with ultrafast laser pulses of various powers are introduced. Plasmonic nanoparticles have been synthesized by pulsed laser ablation of bulk materials. Melting and ablation of nanoparticles have also been used to modify the shape and the size distribution of plasmonic nanoparticle samples. Under certain circumstances, another interesting observation using high power femtosecond laser irradiation of plasmonic nanoparticles is also included in this review, namely the flying, by propulsion of the plasmonic nanoparticles.},
	isbn = {1951-6355},
	doi = {10.1140/epjst/e2008-00432-6},
	author = {Huang, Wenyu and El-Sayed, Mostafa A}
}
@article {1121,
	title = {Some aspects of colloidal nanoparticle stability, catalytic activity, and recycling potential},
	journal = {Topics in Catalysis},
	volume = {47},
	number = {1-2},
	year = {2008},
	note = {Narayanan, Radha El-Sayed, Mostafa A.},
	month = {Mar},
	pages = {15-21},
	abstract = {In this review article, we examine many important aspects of the nanocatalysis field such as size and shape dependent nanocatalysis, the stability of nanoparticles during its catalytic function, and their recycling potential. We provide an overview of some of the work in the literature pertinent to these topics and also discuss some of our own work in these important areas. Some examples of how the catalytic activity is affected by the size of the nanoparticles are discussed as well as how the catalytic process affects the nanoparticle size after its catalytic function. The synthesis of platinum nanoparticles of different shapes is surveyed and the dependence of nanoparticle shape on the catalytic activity is discussed. In addition, changes in the nanoparticle shape and resulting changes in the catalytic activity are also discussed. The recycling potential of the metal nanocatalysts is also highlighted. In addition, a simple examination of the mechanism of nanocatalysis is discussed.},
	isbn = {1022-5528},
	doi = {10.1007/s11244-007-9029-0},
	author = {Narayanan, Radha and El-Sayed, Mostafa A}
}
@article {1126,
	title = {Surface plasmon coupling and its universal size scaling in metal nanostructures of complex geometry: Elongated particle pairs and nanosphere trimers},
	journal = {Journal of Physical Chemistry C},
	volume = {112},
	number = {13},
	year = {2008},
	note = {Jain, Prashant K. El-Sayed, Mostafa A.},
	month = {Apr},
	pages = {4954-4960},
	abstract = {Recently, we showed that the plasmon resonance coupling between two interacting metal nanoparticles decays with the interparticle separation (in units of particle size) with the same universal trend independent of particle size or shape, metal type, or medium. This universal scaling behavior has been shown to apply to lithographically fabricated nanoparticle pairs, the metal nanoshell, plasmonic dielectric sensors, and the plasmon ruler useful in determining intersite distances in biological systems. In this article, we use electrodynamic simulations to examine the general applicability of this universal scaling behavior to more complex nanostructure geometries, for example, head-to-tail dimers of elongated particles of different aspect ratios and curvatures and a trimer of nanospheres. We find that the plasmon coupling between two elongated nanoparticles interacting head-to-tail decays according to the same universal law if the interparticle separation is scaled by the particle long-axis dimension. The absolute plasmon coupling strength, however, depends on the particle shape (i.e., aspect ratio and curvature), without affecting the universal scaling behavior. We also show that universal scaling is valid in a system of three interacting nanospheres, a first step toward extending this model to chains/arrays/assemblies of metal nanoparticles.},
	isbn = {1932-7447},
	doi = {10.1021/jp7120356},
	author = {Jain, Prashant K and El-Sayed, Mostafa A}
}
@article {1132,
	title = {Time-resolved investigation of the acoustic vibration of a single gold nanoprism pair},
	journal = {Journal of Physical Chemistry C},
	volume = {112},
	number = {30},
	year = {2008},
	note = {Burgin, J. Langot, P. Del Fatti, N. Vallee, F. Huang, W. El-Sayed, M. A.},
	month = {Jul},
	pages = {11231-11235},
	abstract = {The acoustic vibration of single gold nanoprism pairs on a glass substrate has been investigated in the time-domain combining a spatial modulation spectroscopy microscope with a high-sensitivity femtosecond pump-probe setup. Three modes were observed and ascribed to two in-plane and one out-of-plane vibration of the nanoprisms forming the pair, in agreement with a theoretical analysis. The periods of the two former modes with similar nature show weak (about 10\%) and well correlated pair to pair fluctuations that can be unambiguously ascribed to variation of the prism geometry. In contrast, strong fluctuations, by almost a factor of 6, of the mode damping are evidenced with no correlation with their period. This indicates large variations of the prism-substrate coupling, providing a unique way for its local investigation.},
	isbn = {1932-7447},
	doi = {10.1021/jp802365s},
	author = {Burgin, J. and Langot, P. and Del Fatti, N. and Vallee, F. and Huang, Wenyu and El-Sayed, Mostafa A}
}
@article {1139,
	title = {Au nanoparticles target cancer},
	journal = {Nano Today},
	volume = {2},
	number = {1},
	year = {2007},
	note = {Jain, Prashant K. El-Sayed, Ivan H. El-Sayed, Mostafa A.},
	month = {Feb},
	pages = {18-29},
	abstract = {Nanoparticles with unique optical properties, facile surface chemistry, and appropriate size scale are generating much enthusiasm in molecular biology and medicine. Noble metal, especially Au, nanoparticles have immense potential for cancer diagnosis and therapy on account of their surface plasmon resonance (SPR) enhanced light scattering and absorption. Conjugation of Au nanoparticles to ligands specifically targeted to biomarkers on cancer cells allows molecular-specific imaging and detection of cancer. Additionally, Au nanoparticles efficiently convert the strongly absorbed light into localized heat, which can be exploited for the selective laser photothermal therapy of cancer. We discuss recent advances in the study and use of selectively targeted Au nanospheres in cancer photodiagnostics and photothermal therapy. By changing the shape or composition of Au nanoparticles, the SPR can be tuned to the near-infrared region, allowing in vivo imaging and photothermal therapy of cancer. The use of Au nanorods and silica-Au core-shell nanoparticles for in vivo cancer detection and therapy is discussed.},
	isbn = {1748-0132},
	doi = {10.1016/s1748-0132(07)70016-6},
	author = {Jain, Prashant K and El Sayed, I.H. and El-Sayed, Mostafa A}
}
@article {1141,
	title = {Cancer cells assemble and align gold nanorods conjugated to antibodies to produce highly enhanced, sharp, and polarized surface Raman spectra: A potential cancer diagnostic marker},
	journal = {Nano Letters},
	volume = {7},
	number = {6},
	year = {2007},
	note = {Huang, Xiaohua El-Sayed, Ivan H. Qian, Wei El-Sayed, Mostafa A.},
	month = {Jun},
	pages = {1591-1597},
	abstract = {Human oral cancer cells are found to assemble and align gold nanorods conjugated to anti-epidermal growth factor receptor (anti-EGFR) antibodies. Immnoconjugated gold nanorods and nanospheres were shown previously to exhibit strong Rayleigh (Mie) scattering useful for imaging. In the present letter, molecules near the nanorods on the cancer cells are found to give a Raman spectrum that is greatly enhanced (due to the high surface plasmon field of the nanorod assembly in which their extended surface plasmon fields overlap), sharp (due to a homogeneous environment), and polarized (due to anisotropic alignments). These observed properties can be used as diagnostic signatures for cancer cells.},
	isbn = {1530-6984},
	doi = {10.1021/nl070472c},
	author = {Huang, Xiaohua and El Sayed, I.H. and Qian, Wei and El-Sayed, Mostafa A}
}
@article {1136,
	title = {Change in titania structure from amorphousness to crystalline increasing photoinduced electron-transfer rate in dye-titania system},
	journal = {Journal of Physical Chemistry C},
	volume = {111},
	number = {26},
	year = {2007},
	note = {Nishikiori, Hiromasa Qian, Wei El-Sayed, Mostafa A. Tanaka, Nobuaki Fujii, Tsuneo},
	month = {Jul},
	pages = {9008-9011},
	abstract = {Thin titania gel films containing well-dispersed fluorescein dye were prepared by the sol-gel method and treated with steam to promote crystal growth of the titania particles. It is known that steam treatment converts the titania structure from amorphousness to crystalline. In the present study, such change is found to increase the rate of the photoinduced electron transfer from and to dispersed fluorescein dye molecules.},
	isbn = {1932-7447},
	doi = {10.1021/jp072625q},
	author = {Nishikiori, H. and Qian, Wei and El-Sayed, Mostafa A and Tanaka, N. and Fujii, T.}
}
@article {1134,
	title = {Dependence of the threshold energy of femtosecond laser ejection of gold nanoprisms from quartz substrates on the nanoparticle environment},
	journal = {Journal of Physical Chemistry C},
	volume = {111},
	number = {25},
	year = {2007},
	note = {Tabor, Christopher Qian, Wei El-Sayed, Mostafa A.},
	month = {Jun},
	pages = {8934-8941},
	abstract = {Recently, it was reported that gold nanoprisms in a monolayer array on a quartz substrate were ejected in air when irradiated with femtosecond laser pulses near their surface plasmon absorption maximum. It was deduced from the measured reduction in particle thickness upon irradiation that the ejection mechanism involved ablation of surface atoms from the gold particle, which generates an intense pressure at the particle-substrate interface. The present study reports on this phenomenon when the substrate-bound nanoparticle is immersed in a liquid environment. In this system, it is found that the nanoparticle ejection requires less than one tenth the energy required if the system was irradiated in air. The ejected nanoparticle is also found to increase in thickness instead of the decrease observed in air. These results suggest another photoinitiated ejection mechanism, different from surface ablation, when the particles are surrounded by a liquid environment. From this and other spectroscopic and microscopic results on the ejected nanoprisms, we suggest a mechanism that involves energy transfer from the photoexcited nanoprism to the solvent within cavities and defects at the particle-substrate interface. The hot-solvent molecules result in an intense pressure at the particle-substrate interface, resulting in particle ejection. Ejection is proposed to consist of two processes, namely nanoparticle-substrate dissociation and nanoparticle solvation and diffusion away from the substrate. These two processes have independently been studied as a function of solvent property.},
	isbn = {1932-7447},
	doi = {10.1021/jp070282q},
	author = {Tabor, C. E. and Qian, Wei and El-Sayed, Mostafa A}
}
@article {1143,
	title = {The effect of plasmon field on the coherent lattice phonon oscillation in electron-beam fabricated gold nanoparticle pairs},
	journal = {Nano Letters},
	volume = {7},
	number = {10},
	year = {2007},
	note = {Huang, Wenyu Qian, Wei Jain, Prashant K. El-Sayed, Mostafa A.},
	month = {Oct},
	pages = {3227-3234},
	abstract = {By using electron beam lithography, we fabricated pairs of gold nanoparticles with varying interparticle separation. Double-beam femtosecond transient absorption spectroscopy was used to determine the coherent lattice oscillation frequency as a function of the interparticle separation in the presence of the plasmon field excited by the monitoring probe light. We found that the fractional shift in the coherent lattice phonon oscillation frequency follows an exponential decay with respect to the interparticle gap scaled by the disc diameter with the same decay constant as that previously observed for the fractional shift in the surface plasmon electronic oscillation resonance frequency. This strongly suggests that it is the near-field coupling between the particles that shifts both the coherent electronic oscillation (plasmon) frequency and the coherent lattice oscillation (phonon) frequency. The similar trend in the effect of interparticle coupling on the plasmon frequency and the phonon frequency is essentially a reflection of the universal scaling behavior of the distance decay of the interparticle plasmonic near-field. It is shown that the observed decrease in the lattice oscillation frequency with decrease in the interparticle distance is the result of a reduction in the effective free electron density within each nanoparticle pair partner as a result of the polarizing perturbation of the plasmonic field of the other nanoparticle in the pair.},
	isbn = {1530-6984},
	doi = {10.1021/nl071813p},
	author = {Huang, Wenyu and Qian, Wei and Jain, Prashant K and El-Sayed, Mostafa A}
}
@article {1145,
	title = {Effect of plasmonic gold nanoparticles on benign and malignant cellular autofluorescence: A novel probe for fluorescence based detection of cancer},
	journal = {Technology in Cancer Research \& Treatment},
	volume = {6},
	number = {5},
	year = {2007},
	note = {El-Sayed, Ivan Huang, Xiaohua Macheret, Fima Humstoe, Joseph Oren Kramer, Randall El-Sayed, Mostafa},
	month = {Oct},
	pages = {403-412},
	abstract = {Due to the strong surface fields of noble metal nanoparticles, absorption and scattering of electromagnetic radiation is greatly enhanced. Noble metallic nanoparticles represent potential novel optical probes for simultaneous molecular imaging and photothermal cancer therapy using the enhanced scattering and absorption of light. Further, gold nanoparticles can affect molecular fluorescence via chemical, electronic, or photonic interactions. Live cells generate fluorescence due to intracellular and extracellular molecules. Differences in the biochemical composition between healthy and malignant cells can be exploited in vivo to help identify cancer spectroscopically. The interaction of gold nanoparticles with cellular autofluorescence has not yet been characterized. We hypothesized that gold nanoparticles delivered to live cells in vitro would alter cellular autofluorescence and may be useful as a novel class of contrast agent for fluorescence based detection of cancer. The fluorescence of two fluorophores that are responsible for tissue autofluorescence, NADH and collagen, and of two oral squamous carcinoma cell lines and one immortalized benign epithelial cell line were measured in vitro. Gold nanoparticles of different shapes, both spheres and rods, quenched the fluorescence of the soluble NADH and collagen. Reduction of NADH fluorescence was due to oxidation of NADH to NAD+ catalyzed by gold nanoparticles (results we previously published). Reduction of collagen fluorescence appears due to photonic absorption of light. Furthermore, a mean quenching of 12/8\% (p < 0.00050) of the tissue autofluorescence of cell suspensions was achieved in this model when nanospheres were incubated with the live cells. Gold nanospheres significantly decrease cellular autofluorescence of live cells under physiological conditions when excited at 280nm. This is the first report to our knowledge to suggest the potential of developing targeted gold nanoparticles optical probes as contrast agents for fluorescence based diagnoses of cancer.},
	isbn = {1533-0346},
	author = {El Sayed, I.H. and Huang, Xiaohua and Macheret, F. and Humstoe, J. O. and Kramer, R. and El-Sayed, Mostafa A}
}
@article {1144,
	title = {Effect of the lattice crystallinity on the electron-phonon relaxation rates in gold nanoparticles},
	journal = {Journal of Physical Chemistry C},
	volume = {111},
	number = {29},
	year = {2007},
	note = {Huang, Wenyu Qian, Wei El-Sayed, Mostafa A. Ding, Yong Wang, Zhong Lin},
	month = {Jul},
	pages = {10751-10757},
	abstract = {In order to study the importance of surface phonons on the electron-phonon relaxation in plasmonic nanoparticles, the effect of size, shape, and materials have recently been studied. Gold and silver nanoparticles have shown no dependence on size and shape while copper nanoparticles have shown some size dependence. This suggests that the bulk phonons, which are sensitive to the bulk-phase structure, are solely responsible for the relaxation of the hot electron in gold and silver plasmonic nanoparticles. The importance of bulk phonons should depend on the degree of crystallinity. In the present study, we have found that the electron-phonon relaxation rate decreases greatly when polycrystalline prismatic gold nanoparticles are annealed and transformed into nearly single-crystalline nanospheres. The results are explained by the presence of high-density grain boundaries with dense, high-frequency molecular type vibrations which are effective in removing the energy of the excited electrons in the polycrystalline prismatic nanoparticles.},
	isbn = {1932-7447},
	doi = {10.1021/jp0738917},
	author = {Huang, Wenyu and Qian, Wei and El-Sayed, Mostafa A and Ding, Y. and Wang, Z.L.}
}
@article {1140,
	title = {Gold nanoparticles: interesting optical properties and recent applications in cancer diagnostic and therapy},
	journal = {Nanomedicine},
	volume = {2},
	number = {5},
	year = {2007},
	note = {Huang, Xiaohua Jain, Prashant K. El-Sayed, Ivan H. El-Sayed, Mostafa A.},
	month = {Oct},
	pages = {681-693},
	abstract = {Recent years have seen tremendous progress in the design and study of nanomaterials geared towards biological and biomedical applications, most notable among these being the noble metal nanoparticles. In this review, we outline the surface-plasmon resonance-enhanced optical properties of colloidal gold nanoparticles directed towards recent biomedical applications with an emphasis on cancer diagnostics and therapeutics. Methods of molecular-specific diagnostics/detection of cancer, including strongly enhanced surface plasmon resonance light-scattering, surface-enhanced emission of gold nanorods and surf ace-enhanced Raman scattering, are described. We also discuss the plasmonic photothermal therapy of cancer achieved by using the strongly enhanced surface-plasmon resonance absorption of gold nanospheres and nanorods.},
	isbn = {1743-5889},
	doi = {10.2217/17435889.2.5.681},
	author = {Huang, Xiaohua and Jain, Prashant K and El Sayed, I.H. and El-Sayed, Mostafa A}
}
@article {1294,
	title = {Multicolorimetric plasmonic gold nanoparticles for 8 optical detection of oral squamous carcinoma},
	journal = {Oral Oncology},
	volume = {43},
	year = {2007},
	note = {El-Sayed, I. Huang, X. El-Sayed, M.1st World Congress of the International-Academy-of-Oral-OncologyMay 17-20, 2007Amsterdam, NETHERLANDSInt Acad Oral OncolS},
	month = {05/2007},
	pages = {121-121},
	issn = {1368-8375},
	author = {El Sayed, I.H. and Huang, X. and El-Sayed, Mostafa A}
}
@article {1135,
	title = {Peptide-conjugated gold nanorods for nuclear targeting},
	journal = {Bioconjugate Chemistry},
	volume = {18},
	number = {5},
	year = {2007},
	note = {Oyelere, Adegboyega K. Chen, Po C. Huang, Xiaohua El-Sayed, Ivan H. El-Sayed, Mostafa A.},
	month = {Sep-Oct},
	pages = {1490-1497},
	abstract = {Resonant electron oscillations on the surface of noble metal nanoparticles (Au, Ag, Cu) create the surface plasmon resonance (SPR) that greatly enhances the absorption and Rayleigh (Mie) scattering of light by these particles. By adjusting the size and shape of the particles from spheres to rods, the SPR absorption and scattering can be tuned from the visible to the near-infrared region (NIR) where biologic tissues are relatively transparent. Further, gold nanorods greatly enhance surface Raman scattering of adsorbed molecules. These unique properties make gold nanorods especially attractive as optical sensors for biological and medical applications. In the present work, gold nanorods are covalently conjugated with a nuclear localization signal peptide through a thioalkyl-triazole linker and incubated with an immortalized benign epithelial cell line and an oral cancer cell line. Dark field light SPR scattering images demonstrate that nanorods are located in both the cytoplasm and nucleus of both cell lines. Single cell micro-Raman spectra reveal enhanced Raman bands of the peptide as well as molecules in the cytoplasm and the nucleus. Further, the Raman spectra reveal a difference between benign and cancer cell lines. This work represents an important step toward both imaging and Raman-based intracellular biosensing with covalently linked ligand-nanorod probes.},
	isbn = {1043-1802},
	doi = {10.1021/bc070132i},
	author = {Oyelere, A. K. and Chen, P. C. and Huang, Xiaohua and El Sayed, I.H. and El-Sayed, Mostafa A}
}
@article {1142,
	title = {The potential use of the enhanced nonlinear properties of gold nanospheres in photothermal cancer therapy},
	journal = {Lasers in Surgery and Medicine},
	volume = {39},
	number = {9},
	year = {2007},
	note = {Huang, Xiaohua Qian, Wei El-Sayed, Ivan H. El-Sayed, Mostafa A.},
	month = {Oct},
	pages = {747-753},
	abstract = {Background and Objective: Laser photothermal therapy (PTT) is practiced at the moment using short laser pulses. The use of plasmonic nanoparticles as contrast agents can decrease the laser energy by using the optical property of the nanoparticles and improve the tumor selectivity by the molecular probes on the particle surface. In this study, we aim at selective and efficient PTT by exploiting the nonlinear optical properties of aggregated spherical gold nanoparticles conjugated to anti-epidermal growth factor receptor (anti-EGFR) antibodies using short NIR laser pulses. Study Design/Materials and Methods: Spherical gold nanoparticles are synthesized and conjugated to anti-EGFR antibodies to specifically target HSC oral cancer cells. The nanoparticles are characterized by micro-absorption spectra and dark field light scattering imaging. Photothermal destructions of control and nanoparticle treated cancer cells are carried out with a ferntosecond Ti:Sapphire laser at 800 nm with a pulse duration of 100 femtoseconds and repetition rate of 1 kHz. Results: The laser power threshold for the photothermal destruction of cells after the nanoparticle treatment is found to be 20 times lower than that required to destroy the cells in the normal PTT, that is, without nanoparticles. The number of destroyed cells is quadratically dependent on the laser power. The number of dead cells shows a nonlinear dependence on the concentration of gold nanoparticles that are specifically targeted to cancer cells. Conclusions: The energy threshold and selectivity of PTT can greatly benefit from the use of the plasmonic enhanced nonlinear optical processes of spherical gold nanoparticles conjugated to anti-EGFR antibodies. The quadratic dependence of the photothermal efficiency on the pulsed NIR laser power indicates a second harmonic generation or a two photon absorption process. The observed nonlinear dependence on the gold nanoparticle concentration suggests that aggregated nanospheres are responsible for the observed enhanced photothermal destruction of the cells.},
	isbn = {0196-8092},
	doi = {10.1002/lsm.20577},
	author = {Huang, Xiaohua and Qian, Wei and El Sayed, I.H. and El-Sayed, Mostafa A}
}
@article {814,
	title = {Reaction of Platinum Nanocatalyst with the Ferricyanide Reactant to Produce Prussian Blue Analogue Complexes},
	journal = {The Journal of Physical Chemistry C},
	volume = {111},
	year = {2007},
	note = {doi: 10.1021/jp709735n},
	month = {2007},
	pages = {17180 - 17183},
	publisher = {American Chemical Society},
	abstract = {The field of catalysis with colloidal nanoparticles is in its infancy. The question of whether the catalysis occurs on the surface of the nanoparticle (thus heterogeneous) or homogeneously in solution using a complex made by the nanoparticle is now being debated. Thus, the molecular mechanism of nanocatalysis has not yet been studied in detail. The first step in this effort is to study the molecular mechanism of the reaction of each reactant with the nanoparticle. This letter is an effort in this direction. A great deal of research has used platinum nanoparticles (PtNPs) to catalyze electron-transfer reactions such as that between thiosulfate and hexacyanoferrate III. We monitored this reaction in detail using optical, Raman, and IR spectroscopies. By increasing the reaction time, two sequential dominant species are formed. The first one is found to have spectral signatures of a Prussian blue analogue with a structure of K[PtIIFeIII(CN)6]. With increasing time, the intensity of the spectrum of this complex is found to decrease, whereas a spectrum similar to that of a complex having the structure of [PtIVFeII(CN)6] increased. A mechanism for the formation of these metal-mixed valency Prussian blue analogues is given.The field of catalysis with colloidal nanoparticles is in its infancy. The question of whether the catalysis occurs on the surface of the nanoparticle (thus heterogeneous) or homogeneously in solution using a complex made by the nanoparticle is now being debated. Thus, the molecular mechanism of nanocatalysis has not yet been studied in detail. The first step in this effort is to study the molecular mechanism of the reaction of each reactant with the nanoparticle. This letter is an effort in this direction. A great deal of research has used platinum nanoparticles (PtNPs) to catalyze electron-transfer reactions such as that between thiosulfate and hexacyanoferrate III. We monitored this reaction in detail using optical, Raman, and IR spectroscopies. By increasing the reaction time, two sequential dominant species are formed. The first one is found to have spectral signatures of a Prussian blue analogue with a structure of K[PtIIFeIII(CN)6]. With increasing time, the intensity of the spectrum of this complex is found to decrease, whereas a spectrum similar to that of a complex having the structure of [PtIVFeII(CN)6] increased. A mechanism for the formation of these metal-mixed valency Prussian blue analogues is given.},
	isbn = {1932-7447},
	doi = {10.1021/jp709735n},
	url = {http://dx.doi.org/10.1021/jp709735n},
	author = {Mahmoud, M A and El-Sayed, Mostafa A}
}
@article {815,
	title = {Review of some interesting surface plasmon resonance-enhanced properties of noble metal nanoparticles and their applications to biosystems},
	journal = {Plasmonics},
	volume = {2},
	year = {2007},
	pages = {107-118},
	publisher = {Springer},
	abstract = {Noble metal, especially gold (Au) and silver (Ag) nanoparticles exhibit unique and tunable optical properties on account of their surface plasmon resonance (SPR). In this review, we discuss the SPR-enhanced optical properties of noble metal nanoparticles, with an emphasis on the recent advances in the utility of these plasmonic properties in molecular-specific imaging and sensing, photo-diagnostics, and selective photothermal therapy. The strongly enhanced SPR scattering from Au nanoparticles makes them useful as bright optical tags for molecular-specific biological imaging and detection using simple dark-field optical microscopy. On the other hand, the SPR absorption of the nanoparticles has allowed their use in the selective laser photothermal therapy of cancer. We also discuss the sensitivity of the nanoparticle SPR frequency to the local medium dielectric constant, which has been successfully exploited for the optical sensing of chemical and biological analytes. Plasmon coupling between metal nanoparticle pairs is also discussed, which forms the basis for nanoparticle assembly-based biodiagnostics and the plasmon ruler for dynamic measurement of nanoscale distances in biological systems.},
	isbn = {1557-1955},
	doi = {10.1007/s11468-007-9031-1},
	url = {http://dx.doi.org/10.1007/s11468-007-9031-1},
	author = {Jain, Prashant K and Huang, Xiaohua and El Sayed, I.H. and El-Sayed, Mostafa A}
}
@article {813,
	title = {Surface Plasmon Resonance Sensitivity of Metal Nanostructures:  Physical Basis and Universal Scaling in Metal Nanoshells},
	journal = {The Journal of Physical Chemistry C},
	volume = {111},
	year = {2007},
	note = {doi: 10.1021/jp0773177},
	month = {2007},
	pages = {17451 - 17454},
	publisher = {American Chemical Society},
	abstract = {In this letter, we show using extended Mie theory simulations that the sensitivity of the surface plasmon resonance (SPR) of a dielectric core-metal nanoshell increases near-exponentially as the ratio of the shell thickness-to-core radius is decreased. The plasmon sensitivity thus shows the same universal scaling behavior established recently for plasmon coupling in metal nanoshells and that in metal nanoparticle pairs. From these observations, we propose that the sensitivity is determined by the ease of surface polarization of the electrons in the nanostructure by the light. This can be used as a generalized physical principle for designing plasmonic nanostructures for effective SPR chemical and biological sensing.In this letter, we show using extended Mie theory simulations that the sensitivity of the surface plasmon resonance (SPR) of a dielectric core-metal nanoshell increases near-exponentially as the ratio of the shell thickness-to-core radius is decreased. The plasmon sensitivity thus shows the same universal scaling behavior established recently for plasmon coupling in metal nanoshells and that in metal nanoparticle pairs. From these observations, we propose that the sensitivity is determined by the ease of surface polarization of the electrons in the nanostructure by the light. This can be used as a generalized physical principle for designing plasmonic nanostructures for effective SPR chemical and biological sensing.},
	isbn = {1932-7447},
	doi = {10.1021/jp0773177},
	url = {http://dx.doi.org/10.1021/jp0773177},
	author = {Jain, Prashant K and El-Sayed, Mostafa A}
}
@article {1137,
	title = {On the universal scaling behavior of the distance decay of plasmon coupling in metal nanoparticle pairs: A plasmon ruler equation},
	journal = {Nano Letters},
	volume = {7},
	number = {7},
	year = {2007},
	note = {Jain, Prashant K. Huang, Wenyu El-Sayed, Mostafa A.},
	month = {Jul},
	pages = {2080-2088},
	abstract = {Localized surface plasmon resonances (LSPR) in lithographically fabricated gold (Au) nanodisc pairs are investigated using microabsorption spectroscopy and electrodynamic simulations. In agreement with previous work, we find that the fractional plasmon wavelength shift for polarization along the interparticle axis decays nearly exponentially with the interparticle gap. In addition, we find that the decay length is roughly about 0.2 in units of the particle size for different nanoparticle size, shape, metal type, or medium dielectric constant. The near-exponential distance decay and the interesting "universal" scaling behavior of interparticle plasmon coupling can be qualitatively explained on the basis of a dipolar-coupling model as being due to the interplay of two factors: the direct dependence of the single-particle polarizability on the cubic power of the particle dimension and the decay of the plasmonic near-field as the cubic power of the inverse distance. Using this universal scaling behavior, we are able to derive a "plasmon ruler equation" that estimates the interparticle separation between Au nanospheres in a biological system from the observed fractional shift of the plasmon band. We find good agreement of the interparticle separations estimated using this equation with the experimental observations of Reinhard et al.},
	isbn = {1530-6984},
	doi = {10.1021/nl071008a},
	author = {Jain, Prashant K and Huang, Wenyu and El-Sayed, Mostafa A}
}
@article {1138,
	title = {Universal scaling of plasmon coupling in metal nanostructures: Extension from particle pairs to nanoshells},
	journal = {Nano Letters},
	volume = {7},
	number = {9},
	year = {2007},
	note = {Jain, Prashant K. El-Sayed, Mostafa A.},
	month = {Sep},
	pages = {2854-2858},
	abstract = {It has been recently shown that the strength of plasmon coupling between a pair of plasmonic metal nanoparticles falls as a function of the interparticle gap scaled by the particle size with a near-exponential decay trend that is universally independent of nanoparticle size, shape, metal type, or medium dielectric constant. In this letter, we extend this universal scaling behavior to the dielectric core-metal shell nanostructure. By using extended Mie theory simulations of silica core-metal nanoshells, we show that when the shift of the nanoshell plasmon resonance wavelength scaled by the solid nanosphere resonance wavelength is plotted against the shell thickness scaled by the core radius, nanoshells with different dimensions (radii) exhibit the same near-exponential decay. Thus, the nanoshell system becomes physically analogous to the particle-pair system, i.e., the nanoshell plasmon resonance results from the coupling of the inner shell surface (cavity) and the outer shell surface (sphere) plasmons over a separation distance essentially given by the metal shell thickness, which is consistent with the plasmon hybridization model of Prodan, Halas, and Nordlander. By using the universal scaling behavior in the nanoshell system, we propose a simple expression for predicting the dipolar plasmon resonance of a silica-gold nanoshell of given dimensions.},
	isbn = {1530-6984},
	doi = {10.1021/nl071496m},
	author = {Jain, Prashant K and El-Sayed, Mostafa A}
}
@article {1150,
	title = {Calculated absorption and scattering properties of gold nanoparticles of different size, shape, and composition: Applications in biological imaging and biomedicine},
	journal = {Journal of Physical Chemistry B},
	volume = {110},
	number = {14},
	year = {2006},
	note = {Jain, PK Lee, KS El-Sayed, IH El-Sayed, MA},
	month = {Apr},
	pages = {7238-7248},
	abstract = {The selection of nanoparticles for achieving efficient contrast for biological and cell imaging applications, as well as for photothermal therapeutic applications, is based on the optical properties of the nanoparticles. We use Mie theory and discrete dipole approximation method to calculate absorption and scattering efficiencies and optical resonance wavelengths for three commonly used classes of nanoparticles: gold nanospheres, silica-gold nanoshells, and gold nanorods. The calculated spectra clearly reflect the well-known dependence of nanoparticle optical properties viz. the resonance wavelength, the extinction cross-section, and the ratio of scattering to absorption, on the nanoparticle dimensions. A systematic quantitative study of the various trends is presented. By increasing the size of gold nanospheres from 20 to 80 nm, the magnitude of extinction as well as the relative contribution of scattering to the extinction rapidly increases. Gold nanospheres in the size range commonly employed (similar to 40 nm) show an absorption cross-section 5 orders higher than conventional absorbing dyes, while the magnitude of light scattering by 80-nm gold nanospheres is 5 orders higher than the light emission from strongly fluorescing dyes. The variation in the plasmon wavelength maximum of nanospheres, i.e., from similar to 520 to 550 nm, is however too limited to be useful for in vivo applications. Gold nanoshells are found to have optical cross-sections comparable to and even higher than the nanospheres. Additionally, their optical resonances lie favorably in the near-infrared region. The resonance wavelength can be rapidly increased by either increasing the total nanoshell size or increasing the ratio of the core-to-shell radius. The total extinction of nanoshells shows a linear dependence on their total size, however, it is independent of the core/shell radius ratio. The relative scattering contribution to the extinction can be rapidly increased by increasing the nanoshell size or decreasing the ratio of the core/shell radius. Gold nanorods show optical cross-sections comparable to nanospheres and nanoshells, however, at much smaller effective size. Their optical resonance can be linearly tuned across the near-infrared region by changing either the effective size or the aspect ratio of the nanorods. The total extinction as well as the relative scattering contribution increases rapidly with the effective size, however, they are independent of the aspect ratio. To compare the effectiveness of nanoparticles of different sizes for real biomedical applications, size-normalized optical cross-sections or per micron coefficients are calculated. Gold nanorods show per micron absorption and scattering coefficients that are an order of magnitude higher than those for nanoshells and nanospheres. While nanorods with a higher aspect ratio along, with a smaller effective radius are the best photoabsorbing nanoparticles, the highest scattering contrast for imaging applications is obtained from nanorods of high aspect ratio with a larger effective radius.},
	isbn = {1520-6106},
	doi = {10.1021/jp057170o},
	author = {Jain, Prashant K and Lee, K. S. and El Sayed, I.H. and El-Sayed, Mostafa A}
}
@article {1153,
	title = {Cancer cell imaging and photothermal therapy in the near-infrared region by using gold nanorods},
	journal = {Journal of the American Chemical Society},
	volume = {128},
	number = {6},
	year = {2006},
	note = {Huang, XH El-Sayed, IH Qian, W El-Sayed, MA},
	month = {Feb},
	pages = {2115-2120},
	abstract = {Due to strong electric fields at the surface, the absorption and scattering of electromagnetic radiation by noble metal nanoparticles are strongly enhanced. These unique properties provide the potential of designing novel optically active reagents for simultaneous molecular imaging and photothermal cancer therapy. It is desirable to use agents that are active in the near-infrared (NIR) region of the radiation spectrum to minimize the light extinction by intrinsic chromophores in native tissue. Gold nanorods with suitable aspect ratios (length divided by width) can absorb and scatter strongly in the NIR region (650-900 nm). In the present work, we provide an in vitro demonstration of gold nanorods as novel contrast agents for both molecular imaging and photothermal cancer therapy. Nanorods are synthesized and conjugated to anti-epidermal growth factor receptor (anti-EGFR) monoclonal antibodies and incubated in cell cultures with a nonmalignant epithelial cell line (HaCat) and two malignant oral epithelial cell lines (HOC 313 clone 8 and HSC 3). The anti-EGFR anti body-conjugated nanorods bind specifically to the surface of the malignant-type cells with a much higher affinity due to the overexpressed EGFR on the cytoplasmic membrane of the malignant cells. As a result of the strongly scattered red light from gold nanorods in dark field, observed using a laboratory microscope, the malignant cells are clearly visualized and diagnosed from the nonmalignant cells. It is found that, after exposure to continuous red laser at 800 nm, malignant cells require about half the laser energy to be photothermally destroyed than the nonmalignant cells. Thus, both efficient cancer cell diagnostics and selective photothermal therapy are realized at the same time.},
	keywords = {display},
	isbn = {0002-7863},
	doi = {10.1021/ja057254a},
	author = {Huang, Xiaohua and El Sayed, I.H. and Qian, Wei and El-Sayed, Mostafa A.}
}
@article {1156,
	title = {Determination of the aspect ratio statistical distribution of gold nanorods in solution from a theoretical fit of the observed inhomogeneously broadened longitudinal plasmon resonance absorption spectrum},
	journal = {Journal of Applied Physics},
	volume = {100},
	number = {4},
	year = {2006},
	note = {Eustis, Susie El-Sayed, Mostafa A.},
	month = {Aug},
	abstract = {The determination of the statistical distribution of aspect ratios of a nanorod solution is desirable for experimentally synthesized solutions. The traditional method of using transmission electron microscopy (TEM) images for size determination gives statistically incorrect values due to distortions introduced by TEM sample preparation and by difficulties in counting a sufficiently large number of rods. In the present work, we propose a method to obtain the aspect ratio distribution using the observed longitudinal surface plasmon resonance absorption spectrum of gold nanorods in solution. The observed inhomogeneously broadened spectrum is fitted with a collection of homogeneously broadened spectra of nanorods each with a specific aspect ratio and population contribution using Gans extension [Ann. Phys. 47, 270 (1915)] of Mie theory. The fit generates an aspect ratio distribution for the rods in solution from which the median value and the statistical distribution are determined. This method is statistically more accurate, more convenient, and less expensive than the traditional method of TEM analysis on a solid substrate. (c) 2006 American Institute of Physics.},
	isbn = {0021-8979},
	doi = {10.1063/1.2244520},
	author = {Eustis, Susie and El-Sayed, Mostafa A}
}
@article {1152,
	title = {Determination of the minimum temperature required for selective photothermal destruction of cancer cells with the use of immunotargeted gold nanoparticles},
	journal = {Photochemistry and Photobiology},
	volume = {82},
	number = {2},
	year = {2006},
	note = {Huang, XH Jain, PK El-Sayed, IH El-Sayed, MA},
	month = {Mar-Apr},
	pages = {412-417},
	abstract = {Laser photothermal therapy of cancer with the use of gold nanoparticles immunotargeted to molecular markers on the cell surface has been shown to be an effective modality to selectively kill cancer cells at much lower laser powers than those needed for healthy cells. To elucidate the minimum light dosimetry required to induce cell death, photothermal destruction of two cancerous cell lines and a noncancerous cell line treated with antiepidermal growth factor receptor (anti-EGFR) anti body-conjugated gold nanoparticles is studied, and a numerical heat transport model is used to estimate the local temperature rise within the cells as a result of the laser heating of the gold nanoparticles. It is found that cell samples with higher nanoparticle loading require a lower incident laser power to achieve a certain temperature rise. Numerically estimated temperatures of 70-80 degrees C achieved by heating the gold particles agree well with the measured threshold temperature for destruction of the cell lines by oven heating and those measured in an earlier nanoshell method. Specific binding of anti-EGFR antibody to cancerous cells overexpressing EGFR selectively increases the gold nanoparticle loading within cancerous cells, thus allowing the cancerous cells to be destroyed at lower laser power thresholds than needed for the noncancerous cells. In addition, photothermal therapy using gold nanoparticles requires lower laser power thresholds than therapies using conventional dyes due to the much higher absorption coefficient of the gold nanoparticles.},
	isbn = {0031-8655},
	doi = {10.1562/2005-12-14-ra-754},
	author = {Huang, Xiaohua and Jain, Prashant K and El Sayed, I.H. and El-Sayed, Mostafa A}
}
@article {1293,
	title = {Effect of crystallization on the proton pump function of bR},
	journal = {ISRAPS Bulletin},
	volume = {18},
	year = {2006},
	pages = {52-57},
	author = {Sanii, L. S. and El-Sayed, Mostafa A}
}
@article {1147,
	title = {Gold and silver nanoparticles in sensing and imaging: Sensitivity of plasmon response to size, shape, and metal composition},
	journal = {Journal of Physical Chemistry B},
	volume = {110},
	number = {39},
	year = {2006},
	note = {Lee, Kyeong-Seok El-Sayed, Mostafa A.},
	month = {Oct},
	pages = {19220-19225},
	abstract = {Plasmonic metal nanoparticles have great potential for chemical and biological sensor applications, due to their sensitive spectral response to the local environment of the nanoparticle surface and ease of monitoring the light signal due to their strong scattering or absorption. In this work, we investigated the dependence of the sensitivity of the surface plasmon resonance (frequency and bandwidth) response to changes in their surrounding environment and the relative contribution of optical scattering to the total extinction, on the size and shape of nanorods and the type of metal, that is, Au vs Ag. Theoretical consideration on the surface plasmon resonance condition revealed that the spectral sensitivity, defined as the relative shift in resonance wavelength with respect to the refractive index change of surrounding materials, has two controlling factors: first the bulk plasma wavelength, a property dependent on the metal type, and second on the aspect ratio of the nanorods which is a geometrical parameter. It is found that the sensitivity is linearly proportional to both these factors. To quantitatively examine the dependence of the spectral sensitivity on the nanorod metal composition and the aspect ratio, the discrete dipole approximation method was used for the calculation of optical spectra of Ag-Au alloy metal nanorods as a function of Ag concentration. It is observed that the sensitivity does not depend on the type of the metal but depends largely on the aspect ratio of nanorods. The direct dependence of the sensitivity on the aspect ratio becomes more prominent as the size of nanorods becomes larger. However, the use of larger nanoparticles may induce an excessive broadening of the resonance spectrum due to an increase in the contribution of multipolar excitations. This restricts the sensing resolution. The insensitivity of the plasmon response to the metal composition is attributable to the fact that the bulk plasma frequency of the metal, which determines the spectral dispersion of the real dielectric function of metals and the surface plasmon resonance condition, has a similar value for the noble metals. On the other hand, nanorods with higher Ag concentration show a great enhancement in magnitude and sharpness of the plasmon resonance band, which gives better sensing resolution despite similar plasmon response. Furthermore, Ag nanorods have an additional advantage as better scatterers compared with Au nanorods of the same size.},
	isbn = {1520-6106},
	doi = {10.1021/jp062536y},
	author = {Lee, K. S. and El-Sayed, Mostafa A}
}
@article {1154,
	title = {Gold nanoparticles propulsion from surface fueled by absorption of femtosecond laser pulse at their surface plasmon resonance},
	journal = {Journal of the American Chemical Society},
	volume = {128},
	number = {41},
	year = {2006},
	note = {Huang, Wenyu Qian, Wei El-Sayed, Mostafa A.},
	month = {Oct},
	pages = {13330-13331},
	isbn = {0002-7863},
	doi = {10.1021/ja064328p},
	author = {Huang, Wenyu and Qian, Wei and El-Sayed, Mostafa A}
}
@article {1157,
	title = {Molecular mechanism of the photochemical generation of gold nanoparticles in ethylene glycol: Support for the disproportionation mechanism},
	journal = {Journal of Physical Chemistry B},
	volume = {110},
	number = {29},
	year = {2006},
	note = {Eustis, Susie El-Sayed, Mostafa A.},
	month = {Jul},
	pages = {14014-14019},
	abstract = {It is found that replacement of the chloride ions in tetrachloroauric acid with bulky bromide ions inhibits the formation of gold nanoparticles in the photochemical reduction in ethylene glycol. However, the addition of silver ions to either the bromide or the chloride auric acid solution is found to enhance the rate of gold nano-particle formation. These results are found to be accounted for by the previously proposed mechanism (Eustis, S.; Hsu, H.-Y.; El-Sayed, M. A. J. Phys. Chem. B 2005, 109, 4811) which involves disproportionation of the chloroauric complexes to generate free gold atoms and chloride ions. The steric effects of the bulky bromide ions inhibit the formation of the Au-Au bond needed in the electron transfer process of the disproportionation reaction. The addition of Ag(+) ions results in the formation of insoluble silver halide, which shifts the disproportionation reaction toward the formation of gold atoms and thus the formation of gold nanoparticles.},
	isbn = {1520-6106},
	doi = {10.1021/jp062972k},
	author = {Eustis, Susie and El-Sayed, Mostafa A}
}
@article {1160,
	title = {Observation of optical gain in solutions of CdS quantum dots at room temperature in the blue region},
	journal = {Applied Physics Letters},
	volume = {88},
	number = {26},
	year = {2006},
	note = {Darugar, Q Qian, W El-Sayed, MA},
	month = {Jun},
	abstract = {The optical gain dynamics has been studied for two CdS quantum dot samples dispersed in toluene at room temperature. This was carried out by using femtosecond transient absorption technique with an excitation at 400 nm and gain measurement was studied at the fluorescence maxima (440 and 460 nm). The optical gain lifetime was found to be as long as 20 ps under pump fluence as low as 0.77 mJ/cm(2). The low threshold is the result of long lifetime of electrons and holes and narrow emission bandwidth. These results suggest that CdS quantum dots in solution are excellent gain media for optically pumped high power blue lasers.},
	isbn = {0003-6951},
	doi = {10.1063/1.2217138},
	author = {Darugar, Q. and Qian, Wei and El-Sayed, Mostafa A}
}
@article {1151,
	title = {Plasmon coupling in nanorod assemblies: Optical absorption, discrete dipole approximation simulation, and exciton-coupling model},
	journal = {Journal of Physical Chemistry B},
	volume = {110},
	number = {37},
	year = {2006},
	note = {Jain, Prashant K. Eustis, Susie El-Sayed, Mostafa A.},
	month = {Sep},
	pages = {18243-18253},
	abstract = {The shape anisotropy of nanorods gives rise to two distinct orientational modes by which nanorods can be assembled, i.e., end-to-end and side-by-side, analogous to the well-known H and J aggregation in organic chromophores. Optical absorption spectra of gold nanorods have earlier been observed to show a red-shift of the longitudinal plasmon band for the end-to-end linkage of nanorods, resulting from the plasmon coupling between neighboring nanoparticles, similar to the assembly of gold nanospheres. We observe, however, that side-by-side linkage of nanorods in solution shows a blue-shift of the longitudinal plasmon band and a red-shift of the transverse plasmon band. Optical spectra calculated using the discrete dipole approximation method were used to simulate plasmon coupling in assembled nanorod dimers. The longitudinal plasmon band is found to shift to lower energies for end-to-end assembly, but a shift to higher energies is found for the side-by-side orientation, in agreement with the optical absorption experiments. The strength of plasmon coupling was seen to increase with decreasing internanorod distance and an increase in the number of interacting nanorods. For both side-by-side and end-to-end assemblies, the strength of the longitudinal plasmon coupling increases with increasing nanorod aspect ratio as a result of the increasing dipole moment of the longitudinal plasmon. For both the side-by-side and end-to-end orientation, the simulation of a dimer of nanorods having dissimilar aspect ratios showed a longitudinal plasmon resonance with both a blue-shifted and a red-shifted component, as a result of symmetry breaking. A similar result is observed for a pair of similar aspect ratio nanorods assembled in a nonparallel orientation. The internanorod plasmon coupling scheme concluded from the experimental results and simulations is found to be qualitatively consistent with the molecular exciton coupling theory, which has been used to describe the optical spectra of H and J aggregates of organic molecules. The coupled nanorod plasmons are also suggested to be electromagnetic analogues of molecular orbitals. Investigation of the plasmon coupling in assembled nanorods is important for the characterization of optical excitations and plasmon propagation in these nanostructures. The surface plasmon resonance shift resulting from nanorod assembly also offers a promising alternative for analyte-sensing assays.},
	isbn = {1520-6106},
	doi = {10.1021/jp063879z},
	author = {Jain, Prashant K and Eustis, Susie and El-Sayed, Mostafa A}
}
@article {1158,
	title = {Selective laser photo-thermal therapy of epithelial carcinoma using anti-EGFR antibody conjugated gold nanoparticles},
	journal = {Cancer Letters},
	volume = {239},
	number = {1},
	year = {2006},
	note = {El-Sayed, Ivan H. Huang, Xiaohua El-Sayed, Mostafa A.},
	month = {Jul},
	pages = {129-135},
	abstract = {Efficient conversion of strongly absorbed light by plasmonic gold nanoparticles to heat energy and their easy bioconjugation suggest their use as selective photothermal agents in molecular cancer cell targeting. Two oral squamous carcinoma cell lines (HSC 313 and HOC 3 Clone 8) and one benign epithelial cell line (HaCaT) were incubated with anti-epithelial growth factor receptor (EGFR) antibody conjugated gold nanoparticles and then exposed to continuous visible argon ion laser at 514 nm. It is found that the malignant cells require less than half the laser energy to be killed than the benign cells after incubation with anti-EGFR antibody conjugated Au nanoparticles. No photothermal destruction is observed for all types of cells in the absence of nanoparticles at four times energy required to kill the malignant cells with anti-EGFR/Au conjugates bonded. An nanoparticles thus offer a novel class of selective photothermal agents using a CW laser at low powers. The potential of using this selective technique in molecularly targeted photothermal therapy in vivo is discussed (c) 2005 Elsevier Ireland Ltd. All rights reserved.},
	isbn = {0304-3835},
	doi = {10.1016/j.canlet.2005.07.035},
	author = {El Sayed, I.H. and Huang, Xiaohua and El-Sayed, Mostafa A}
}
@article {1159,
	title = {Size-dependent ultrafast electronic energy relaxation and enhanced fluorescence of copper nanoparticles},
	journal = {Journal of Physical Chemistry B},
	volume = {110},
	number = {1},
	year = {2006},
	note = {Darugar, Q Qian, W El-Sayed, MA Pileni, MP},
	month = {Jan},
	pages = {143-149},
	abstract = {The energy relaxation of the electrons in the conduction band of 12 and 30 nm diameter copper nanoparticles in colloidal solution was investigated using femtosecond time-resolved transient spectroscopy. Experimental results show that the hot electron energy relaxation is faster in 12 nm copper nanoparticles (0.37 ps) than that in 30 nm copper nanoparticles (0.51 ps), which is explained by the size-dependent electron-surface phonon coupling. Additional mechanisms involving trapping or energy transfer processes to the denser surface states (imperfection) in the smaller nanoparticles are needed to explain the relaxation rate in the 12 nm nanoparticles. The observed fluorescence quantum yield from these nanoparticles is found to be enhanced by roughly 5 orders of magnitude for the 30 nm nanoparticles and 4 orders of magnitude for the 12 nm nanoparticles (relative to bulk copper metal). The increase in the fluorescence quantum yield is attributed to the electromagnetic enhancement of the radiative recombination of the electrons in the s-p conduction band below the Fermi level with the holes in the d bands due to the strong surface plasmon oscillation in these nanoparticles.},
	isbn = {1520-6106},
	doi = {10.1021/jp0545445},
	author = {Darugar, Q. and Qian, Wei and El-Sayed, Mostafa A and Pileni, Marie-Paule}
}
@article {1148,
	title = {Ultrafast cooling of photoexcited electrons in gold nanoparticle-thiolated DNA conjugates involves the dissociation of the gold-thiol bond},
	journal = {Journal of the American Chemical Society},
	volume = {128},
	number = {7},
	year = {2006},
	note = {Jain, PK Qian, W El-Sayed, MA},
	month = {Feb},
	pages = {2426-2433},
	abstract = {Using UV-visible extinction spectroscopy and femtosecond pump-probe transient absorption spectroscopy, we have studied the effect of femtosecond laser heating on gold nanoparticles attached to DNA ligands via thiol groups. It is found that femtosecond pulse excitation of the DNA-modified nanoparticles at a wavelength of 400 nm leads to desorption of the thiolated DNA strands from the nanoparticle surface by the dissociation of the gold-sulfur bond. The laser-initiated gold-sulfur bond-breaking process is a new pathway for nonradiative relaxation of the optically excited electrons within the DNA-modified gold nanoparticles, as manifested by a faster decay rate of the excited electronic distribution at progressively higher laser pulse energies. The experimental results favor a bond dissociation mechanism involving the coupling between the photoexcited electrons of the nanoparticles and the gold-sulfur bond vibrations over one involving the conventional phonon-phonon thermal heating processes. The latter processes have been observed previously by our group to be effective in the selective photothermal destruction of cancer cells bound to anti-epidermal growth factor receptor-conjugated gold nanoparticles.},
	isbn = {0002-7863},
	doi = {10.1021/ja056769z},
	author = {Jain, Prashant K and Qian, Wei and El-Sayed, Mostafa A}
}
@article {1149,
	title = {Ultrafast electron relaxation dynamics in coupled metal nanoparticles in aggregates},
	journal = {Journal of Physical Chemistry B},
	volume = {110},
	number = {1},
	year = {2006},
	note = {Jain, PK Qian, W El-Sayed, MA},
	month = {Jan},
	pages = {136-142},
	abstract = {We report the effect of aggregation in gold nanoparticles on their ultrafast electron-phonon relaxation dynamics measured by femtosecond transient absorption pump-probe spectroscopy. UV-visible extinction and transient absorption of the solution-stable aggregates of gold nanoparticles show a broad absorption in the 550-700-nm region in addition to the isolated gold nanoparticle plasmon resonance. This broad red-shifted absorption can be attributed to contributions from gold nanoparticle aggregates with different sizes and/or different fractal structures. The electron-phonon relaxation, reflected as a fast decay component of the transient bleach, is found to depend on the probe wavelength, suggesting that each wavelength interrogates one particular subset of the aggregates. As the probe wavelength is changed from 520 to 635 nm across the broad aggregate absorption, the rate of electron-phonon relaxation increases. The observed trend in the hot electron lifetimes can be explained on the basis of an increased overlap of the electron oscillation frequency with the phonon spectrum and enhanced interfacial electron scattering, with increasing extent of aggregation. The experimental results strongly suggest the presence of intercolloid electronic coupling within the nanoparticle aggregates, besides the well-known dipolar plasmon coupling.},
	isbn = {1520-6106},
	doi = {10.1021/jp055562p},
	author = {Jain, Prashant K and Qian, Wei and El-Sayed, Mostafa A}
}
@article {1146,
	title = {Ultrafast electronic relaxation and charge-carrier localization in CdS/CdSe/CdS quantum-dot quantum-well heterostructures},
	journal = {Nano Letters},
	volume = {6},
	number = {9},
	year = {2006},
	note = {Schill, Alexander W. Gaddis, Christopher S. Qian, Wei El-Sayed, Mostafa A. Cai, Ye Milam, Valeria T. Sandhage, Kenneth},
	month = {Sep},
	pages = {1940-1949},
	abstract = {The relaxation and localization times of excited electrons in CdS/CdSe/CdS colloidal quantum wells were measured using subpicosecond spectroscopy. HRTEM analysis and steady-state PL demonstrate a narrow size distribution of 5-6 nm epitaxial crystallites. By monitoring the rise time of the stimulated emission as a function of pump intensity, the relaxation times of the electron from the CdS core into the CdSe well are determined and assigned. Two-component rise times in the stimulated emission are attributed to intraband relaxation of carriers generated directly within the CdSe well ( fast component) and charge transfer of core-localized carriers across the CdS/CdSe interface ( slow component). This is the first reported observation of simultaneous photon absorption in the core and well of a quantum-dot heterostructure. With increasing pump intensity, the charge-transfer channel between the CdS core CdSe well contributes less to the stimulated emission signal because of filling and saturation of the CdSe well state, making the interfacial charge-transfer component less efficient. The interfacial charge-transfer time of the excited electron was determined from the slow component of the stimulated emission build-up time and is found to have a value of 1.2 ps.},
	isbn = {1530-6984},
	doi = {10.1021/nl061054v},
	author = {Schill, A. W. and Gaddis, C. S. and Qian, Wei and El-Sayed, Mostafa A and Cai, Y. and Milam, V. T. and Sandhage, K.}
}
@article {1155,
	title = {Using silica films and powders modified with benzophenone to photoreduce silver nanoparticles},
	journal = {Journal of Photochemistry and Photobiology a-Chemistry},
	volume = {181},
	number = {2-3},
	year = {2006},
	note = {Eustis, Susie Krylova, Galina Smirnova, Natalie Eremenko, Anna Tabor, Christopher Huang, Wenyu El-Sayed, Mostafa A.},
	month = {Jul},
	pages = {385-393},
	abstract = {Porous silica (SiO2 films and powders), modified with benzophenone (BP), facilitates the formation of stable sliver nanoparticles by taking advantage of the solid supported photosensitizer. The silica serves as a carrier for the BP into an aqueous solution and its subsequent removal. Benzophenone, bound to a silica film, was able to reduce silver ions to generate nanoparticles in solution, while silica powder with bound BP generates silver nanoparticles that are attracted to the silica. Silver nanoparticles are also fabricated in porous silica films by incorporating silver ions into the films before casting and then irradiating the film in a solution containing BP. From pH studies, it is concluded that the ketyl-radicals and anion-radicals of BP and IPA both take part in the reduction of silver ions. These synthetic studies provide a new photochemical reduction method by immobilizing the reactant on a silica surface allowing generation of silver nanoparticles in solution attached to powders or inside a film for catalytic applications or increased conductivity of silica films. (c) 2006 Elsevier B.V. All rights reserved.},
	isbn = {1010-6030},
	doi = {10.1016/j.jphotochem.2005.12.024},
	author = {Eustis, Susie and Krylova, G. and Smirnova, N. and Eremenko, A. and Tabor, C. E. and Huang, Wenyu and El-Sayed, Mostafa A}
}
@article {835,
	title = {Aspect Ratio Dependence of the Enhanced Fluorescence Intensity of Gold Nanorods:  Experimental and Simulation Study},
	journal = {The Journal of Physical Chemistry B},
	volume = {109},
	year = {2005},
	note = {doi: 10.1021/jp052951a},
	month = {2005},
	pages = {16350 - 16356},
	publisher = {American Chemical Society},
	abstract = {Experimental observations and theoretical treatments are carried out for the band shape and relative intensity of the emission from gold nanorods of various aspect ratios in the range between 2.25 (1.5 theory) and 6.0 (9 theory). The calculation of the fluorescence spectra requires knowledge of the nanorod size distribution, the enhancement factors, and the shape of the unenhanced fluorescence spectrum. The size distribution is determined from the fit of the observed absorption spectrum for each value of aspect ratio studied to the theoretical model of Gans. The theory by Boyd and Shen is used for calculating the enhancement of the fluorescence spectrum of the previously observed weak emission of bulk gold, which originates from the interband transition. This is carried out for nanorods of different aspect ratios. To compare theory to the observed nanorod fluorescence spectra, which suffer from self-absorption, the calculated nanorod fluorescence spectra are corrected for this effect using the observed absorption spectra. The comparison between the observed and the calculated fluorescence band shapes is found to be good. The calculated changes in the relative intensities upon changing the aspect ratios are found to be much greater than that observed. This is due to the fact that for the observed emission of all the nanorods studied nonradiative processes dominate the relaxation mechanism of the excited state, a fact that was not included in the theoretical treatments.Experimental observations and theoretical treatments are carried out for the band shape and relative intensity of the emission from gold nanorods of various aspect ratios in the range between 2.25 (1.5 theory) and 6.0 (9 theory). The calculation of the fluorescence spectra requires knowledge of the nanorod size distribution, the enhancement factors, and the shape of the unenhanced fluorescence spectrum. The size distribution is determined from the fit of the observed absorption spectrum for each value of aspect ratio studied to the theoretical model of Gans. The theory by Boyd and Shen is used for calculating the enhancement of the fluorescence spectrum of the previously observed weak emission of bulk gold, which originates from the interband transition. This is carried out for nanorods of different aspect ratios. To compare theory to the observed nanorod fluorescence spectra, which suffer from self-absorption, the calculated nanorod fluorescence spectra are corrected for this effect using the observed absorption spectra. The comparison between the observed and the calculated fluorescence band shapes is found to be good. The calculated changes in the relative intensities upon changing the aspect ratios are found to be much greater than that observed. This is due to the fact that for the observed emission of all the nanorods studied nonradiative processes dominate the relaxation mechanism of the excited state, a fact that was not included in the theoretical treatments.},
	isbn = {1520-6106},
	doi = {10.1021/jp052951a},
	url = {http://dx.doi.org/10.1021/jp052951a},
	author = {Eustis, Susie and El-Sayed, Mostafa A}
}
@article {1164,
	title = {Carbon-supported spherical palladium nanoparticles as potential recyclable catalysts for the Suzuki reaction},
	journal = {Journal of Catalysis},
	volume = {234},
	number = {2},
	year = {2005},
	note = {Narayanan, R El-Sayed, MA},
	month = {Sep},
	pages = {348-355},
	abstract = {Carbon-supported PVP-Pd nanoparticles prepared by adsorption of colloidal PVP-Pd nanoparticles onto activated carbon are used as catalysts for the Suzuki reaction between phenylboronic acid and iodobenzene to form biphenyl. These carbon-supported nanoparticles result in a lower biphenyl yield during the first cycle than the colloidal Pd nanoparticles that we studied previously. The carbon-supported Pd nanoparticles retain 69\% of its activity upon recycling (second cycle), which is almost double the recycling potential observed in colloidal Pd nanoparticles (37\% retention of activity). In addition, the carbon-supported Pd nanoparticles retain 73 +/- 3\% of their catalytic activity during the second through fifth cycles of the Suzuki reaction, while the catalytic activity of the colloidal Pd nanoparticles greatly decreases during that time frame. The carbon support that the palladium nanoparticles are adsorbed onto helps to preserve its catalytic activity for longer time periods. The effect of catalysis and recycling on the nanoparticle size is also investigated. The average size of the carbon-supported palladium nanoparticles is 1.9 +/- 0.1 nm initially, 2.6 +/- 0.1 nm after the first cycle, and 3.1 +/- 0.1 nm after the second cycle. The continued growth of the supported nanoparticles suggests that the carbon support protects the palladium nanoparticles during the harsh Suzuki reaction and prevents aggregation and precipitation unlike the colloidal palladium nanoparticles. In addition, a narrow size distribution during the growth process (Ostwald ripening) is observed for the carbon-supported nanoparticles. This could be due to the adsorption method for preparing carbon-supported Pd nanoparticles because excess unaggregated palladium atoms will not be adsorbed onto the carbon support. (c) 2005 Elsevier Inc. All rights reserved.},
	isbn = {0021-9517},
	doi = {10.1016/j.jcat.2005.06.024},
	author = {Narayanan, Radha and El-Sayed, Mostafa A}
}
@article {1165,
	title = {Catalysis with transition metal nanoparticles in colloidal solution: Nanoparticle shape dependence and stability},
	journal = {Journal of Physical Chemistry B},
	volume = {109},
	number = {26},
	year = {2005},
	note = {Narayanan, R El-Sayed, MA},
	month = {Jul},
	pages = {12663-12676},
	abstract = {While the nanocatalysis field has undergone an explosive growth during the past decade, there have been very few studies in the area of shape-dependent catalysis and the effect of the catalytic process on the shape and size of transition metal nanoparticles as well as their recycling potential. Metal nanoparticles of different shapes have different crystallographic facets and have different fraction of surface atoms on their corners and edges, which makes it interesting to study the effect of metal nanoparticle shape on the catalytic activity of various organic and inorganic reactions. Transition metal nanoparticles are attractive to use as catalysts due to their high surface-to-volume ratio compared to bulk catalytic materials, but their surface atoms could be so active that changes in the size and shape of the nanoparticles could occur during the course of their catalytic function, which could also affect their recycling potential. In this Feature Article, we review our work on the effect of the shape of the colloidal nanocatalyst on the catalytic activity as well as the effect of the catalytic process on the shape and size of the colloidal transition metal nanocatalysts and their recycling potential. These studies provide important clues on the mechanism of the reactions we studied and also can be very useful in the process of designing better catalysts in the future.},
	isbn = {1520-6106},
	doi = {10.1021/jp051066p},
	author = {Narayanan, Radha and El-Sayed, Mostafa A}
}
@article {836,
	title = {Chemistry and properties of nanocrystals of different shapes},
	journal = {Chemical Reviews},
	volume = {105},
	year = {2005},
	pages = {1025-1102},
	publisher = {ACS Publications},
	isbn = {0009-2665},
	doi = {10.1021/cr030063a},
	url = {http://dx.doi.org/10.1021/cr030063a},
	author = {Burda, Clemens and Chen, X. and Narayanan, Radha and El-Sayed, Mostafa A}
}
@article {1172,
	title = {Chemistry curricula in the future},
	journal = {Chemical \& Engineering News},
	volume = {83},
	number = {20},
	year = {2005},
	note = {El-Sayed, MA},
	month = {May},
	pages = {6-6},
	isbn = {0009-2347},
	author = {El-Sayed, Mostafa A}
}
@article {1168,
	title = {Dependence of the enhanced optical scattering efficiency relative to that of absorption for gold metal nanorods on aspect ratio, size, end-cap shape, and medium refractive index},
	journal = {Journal of Physical Chemistry B},
	volume = {109},
	number = {43},
	year = {2005},
	note = {Lee, KS El-Sayed, MA},
	month = {Nov},
	pages = {20331-20338},
	abstract = {The Current intense interest in the properties of plasmonic nanostructures for their applications in chemical and biochemical sensors, medical diagnostics and therapeutics, and biological imaging is fundamentally based on their enhanced optical absorption and scattering properties. In this study, the optical extinction, absorption, and scattering efficiencies were calculated as a function of shape definition, aspect ratio, surrounding medium, and material selection. The discrete dipole approximation method was used, which is known to be a very useful and versatile cornputational too] for particles with any arbitrary shape. Relative contribution of scattering to the total extinction for the longitudinal mode was found to be significantly dependent on the aspect ratio of the nanorod in a somewhat complex manner, different from a typical linear relationship for the resonance wavelength. A slight elongation of An nanosphere gives rise to a drastic increase in the relative scattering efficiency, which eventually reaches a maximum and begins to decrease with further increase in the aspect ratio. This is ascribed to the increasing absorptive contribution from the larger imaginary dielectric function of the metal particle in the longer wavelength region where the red-shifted excitation of the longitudinal resonance mode Occurs. For transverse mode exhibiting the blue-shift in the resonance peak, on the contrary, the absorption efficiency is relatively enhanced compared to the scattering efficiency with increasing aspect ratio. This is thought to result from the dominant effect of the interband transition present in this wavelength re-ion. Besides the dependence of plasmonic characteristics on the aspect ratio of nanorod, the DDA results for a small change of the end-cap shape and the index of the surrounding medium lead us to conclude that there exist two competing key factors: a weighting factor assigned to the shape parameter and the dielectric function of the metal particle, which control the relative enhancement in the scattering and absorption as well as the linearity of resonance wavelength with regard to the aspect ratio.},
	isbn = {1520-6106},
	doi = {10.1021/jp054385p},
	author = {Lee, K. S. and El-Sayed, Mostafa A}
}
@article {1167,
	title = {Effect of colloidal nanocatalysis on the metallic nanoparticle shape: The Suzuki reaction},
	journal = {Langmuir},
	volume = {21},
	number = {5},
	year = {2005},
	note = {Narayanan, R El-Sayed, MA},
	month = {Mar},
	pages = {2027-2033},
	abstract = {Dominantly tetrahedral shaped poly(vinylpyrrolidone) -platinum (PVP-Pt) nanoparticles are shown to catalyze the Suzuki reaction between phenylboronic acid and iodobenzene but are not as active as the spherical palladium nanoparticles studied previously. The dominantly tetrahedral PVP-Pt nanoparticles (55 +/- 4\% regular tetrahedral, 22 +/- 2\% distorted tetrahedral, and 23 +/- 2\% spherical nanoparticles) are synthesized by using the hydrogen reduction method. The transmission electron microscopy (TEM) results show that a transformation of shape from tetrahedral to spherical Pt nanoparticles takes place 3 h into the first cycle of the reaction. After the first cycle, the spherical nanoparticles have a similar size distribution to that of the tetrahedral nanoparticles before the reaction and the observed shape distribution is 18 +/- 6\% regular tetrahedral, 28 +/- 5\% distorted tetrahedral, and 54 +/- 5\% spherical nanoparticles. After the second cycle of the Suzuki reaction, the shape distribution is 13 +/- 5\% regular tetrahedral, 24 +/- 5\% distorted tetrahedral, and 63 +/- 7\% spherical nanoparticles. After the second cycle, the transformed spherical nanoparticles continue to grow, and this could be due to the strong capping action of the higher molecular weight PVP (M-w = 360 000), which makes the nanoparticles more resistant to aggregation and precipitation, unlike the Pd nanoparticles capped with the lower molecular weight PVP (M-w = 40 000) used previously. The transformation in shape also occurs when the nanoparticles are refluxed in the presence of the solvent, sodium acetate, and iodobenzene and results in spherical nanoparticles with a similar size distribution to that of the tetrahedral nanoparticles before any perturbations. However, in the presence of phenylboronic acid, the regular tetrahedral nanoparticles remain dominant (51 6\%) and maintain their size. These results support our previous studies in which we proposed that phenylboronic acid binds to the nanoparticle surface and thus acts as a capping agent for the particle and reacts with the iodobenzene. Recycling the nanoparticles results in a drastic reduction of the catalytic activity, and this must be due to the transformation of shape from the dominantly tetrahedral to the larger dominantly spherical nanoparticles. This also supports results in the literature that show that spherical platinum nanoparticles do not catalyze this reaction.},
	isbn = {0743-7463},
	doi = {10.1021/la047600m},
	author = {Narayanan, Radha and El-Sayed, Mostafa A}
}
@article {1161,
	title = {Femtosecond excitation dynamics in gold nanospheres and nanorods},
	journal = {Physical Review B},
	volume = {72},
	number = {23},
	year = {2005},
	note = {Varnavski, OP Goodson, T Mohamed, MB El-Sayed, MA},
	month = {Dec},
	abstract = {Femtosecond visible photoluminescence is detected from gold nanoparticles using time-resolved fluorescence upconversion spectroscopy. We directly compared this fast luminescence from gold nanospheres (subset of 25 nm) with that obtained from nanorods (subset of 15x40 nm, subset of 15x27 nm) under vis (3.02 eV) and UV(4.65 eV) excitation. A fast (similar to 50 fs) decay was obtained for the nanoparticles and the emission was depolarized. Degenerate femtosecond pump-probe experiments in the low excitation intensity regime demonstrated much slower electron thermalization and/or equilibration dynamics on the time scale of a few hundred femtoseconds. These features strongly indicate a d-hole-conduction electron recombination process as the origin of this photoluminescence. A direct comparison of the fast emission spectra from nanorods and nanospheres is used to discuss the emission enhancement mechanism. These results suggest that the classical local field enhancement theory describes quantitatively well many of the emission features of nanorods with respect to those for nanospheres without invoking more complex models.},
	isbn = {1098-0121},
	doi = {10.1103/PhysRevB.72.235405},
	author = {Varnavski, O. P. and Goodson, T. and Mohamed, MB and El-Sayed, Mostafa A}
}
@article {1166,
	title = {FTIR study of the mode of binding of the reactants on the Pd nanoparticle surface during the catalysis of the Suzuki reaction},
	journal = {Journal of Physical Chemistry B},
	volume = {109},
	number = {10},
	year = {2005},
	note = {Narayanan, R El-Sayed, MA},
	month = {Mar},
	pages = {4357-4360},
	abstract = {In the Suzuki reaction between phenylboronic acid and iodobenzene catalyzed by palladium nanoparticles, our previous studies suggested that the phenylboronic acid adsorbs on the nanoparticle surface and then interacts with the iodobenzene that is present in solution. In the present study, FTIR is used to examine the change in the vibrational frequencies of phenylboronic acid in films with and without the addition of palladium nanoparticles. The large change in the B-O stretching frequency of phenylboronic acid from 1348 to 1376 cm(-1) in the presence of sodium acetate and palladium nanoparticles strongly suggests that the mode of binding of phenylboronic acid to the Pd nanoparticle surface involves a B-O-Pd type of bonding. Shifts in the B-C stretching mode and the out-of-plane phenyl C-C ring deformation bands associated with phenylboronic acid provide additional confirmations of the binding process. It is also shown that the phenylboronic acid needs to be in the deprotonated form in the presence of sodium acetate (phenylboronate anion) to bind to the palladium nanoparticle surface. No changes in the characteristic bands of iodobenzene were observed in films made in the presence of the palladium nanoparticles. The FTIR studies provide proof of the mode of binding that occurs in the nanoparticle Surface for the first time and also confirms the mechanism of the Suzuki reaction that we proposed previously.},
	isbn = {1520-6106},
	doi = {10.1021/jp044659t},
	author = {Narayanan, Radha and El-Sayed, Mostafa A}
}
@article {1171,
	title = {Gold nanoparticle formation from photochemical reduction of Au3+ by continuous excitation in colloidal solutions. A proposed molecular mechanism},
	journal = {Journal of Physical Chemistry B},
	volume = {109},
	number = {11},
	year = {2005},
	note = {Eustis, S Hsu, HY El-Sayed, MA},
	month = {Mar},
	pages = {4811-4815},
	abstract = {A photochemical reduction of Au3+ with continuous 250-400 nm excitation is studied in ethylene Zalycol, and poly (vinylpyrrolidone) (PVP) is used as a capping material. After the absorption of Au3+ disappears, excitation is stopped. The surface plasmon absorption of gold as well as the thermal reappearance of the Au3+ absorption are found to increase as a function of time. The rates of these changes are studied as a function of the mole fraction of ethylene glycol in water. Experimental results show that a small amount of ethylene glycol increases the formation of gold nanoparticles and decreases the reformation of the Au3+ absorption after irradiation. Increasing the glycol concentration first increases the rate of formation of gold nanoparticles to a maximum at a mole fraction 0.40. As the glycol concentration is further increased, the rate of formation of the gold nanoparticles and the rate of re-formation of Au3+ decrease. A mechanism is proposed that involves the reduction of the excited Au3+ to Au2+ by ethylene glycol. This is followed by the disproportionation of Au2+ to Au3+ and Au1+. Both the reduction of Au1+ by ethylene glycol and its disproportionation lead to the formation of Au-0, which upon nucleation and growth form An nanoparticles.},
	isbn = {1520-6106},
	doi = {10.1021/jp0441588},
	author = {Eustis, Susie and Hsu, H. Y. and El-Sayed, Mostafa A}
}
@article {1169,
	title = {Gold nanoparticles: Catalyst for the oxidation of NADH to NAD(+)},
	journal = {Journal of Photochemistry and Photobiology B-Biology},
	volume = {81},
	number = {2},
	year = {2005},
	note = {Huang, XH El-Sayed, IH Yi, XB El-Sayed, MA},
	month = {Nov},
	pages = {76-83},
	abstract = {Nicotinamide adenine dinucleotide is an important coenzyme involved in the production of ATP, the fuel of energy, in every cell. It alternates between the oxidized form NAD(+) and the reduced form dihydronicotinamide adenine dinucleotide (NADH) and serves as a hydrogen and electron carrier in the cellular respiratory processes. In the present work, the catalytic effect of gold nanoparticles on the oxidization of NADH to NAD(+) was investigated. The addition of gold nanoparticles was found to quench the NADH fluorescence intensities but had no effect on the fluorescence lifetime. This suggested that the fluorescence quenching was not due to coupling with the excited state, but due to changing the ground state of NADH. The intensity of the 340 nm absorption band of NADH was found to decrease while that of the 260 nm band of NAD+ was found to increase as the concentration of gold nanoparticles increased. This conversion reaction was further supported by nuclear magnetic resonance and mass spectroscopy. The effect of the addition of NADH was found to slightly red shift and increase the intensity of the surface plasmon absorption band of gold nanoparticles at 520 nm. This gives a strong support that the conversion of NADH to NAD(+) is occurring on the surface of the gold nanoparticles, i.e. NADH is surface catalyzed by the gold nanoparticles. The catalytic property of this important reaction might have important future applications in biological and medical fields. (c) 2005 Elsevier B.V. All rights reserved.},
	isbn = {1011-1344},
	doi = {10.1016/j.jphotobiol.2005.05.010},
	author = {Huang, Xiaohua and El Sayed, I.H. and Yi, X. B. and El-Sayed, Mostafa A}
}
@article {837,
	title = {Growth and fragmentation of silver nanoparticles in their synthesis with a fs laser and CW light by photo-sensitization with benzophenone},
	journal = {Photochemical \& Photobiological Sciences},
	volume = {4},
	year = {2005},
	pages = {154-159},
	publisher = {Royal Society of Chemistry},
	abstract = {The photo-sensitization synthetic technique of making silver nanoparticles using benzophenone is studied using both a laser and a mercury lamp as light sources. The power and irradiation time dependence of the synthesized nanoparticle absorption spectra and their size distribution [as determined by transmission electron microscopy (TEM)] are studied in each method and compared. In the laser synthesis, as either the laser power or the irradiation time increases, the intensity of the surface plasmon resonance absorption at 400 nm is found to increase linearly first, followed by a reduction of the red edge of the plasmon resonance absorption band. The TEM results showed that in the laser synthesis low powers and short irradiation times produce nanoparticles around 20 nm in diameter. Increasing the power or irradiation time produces a second population of nanoparticles with average size of 5 nm in diameter. These small particles are believed to be formed from the surface ablation of the large particles. The surface plasmon absorption band is found to be narrower when the nanoparticles are produced with laser irradiation. Throughout the exposure time with the CW lamp, the plasmon resonance absorption band of the particles formed first grows in intensity, then blue shifts and narrows, and finally red shifts while decreasing in intensity. The TEM results for lamp samples showed particle formation and growth, followed by small nanoparticle formation. The above results are discussed in terms of a mechanism in which, the excited benzophenone forms the ketal radical, which reduces Ag+ in solution and on the Ag nanoparticle surface. As the time of irradiation or the light energy increases the benzophenone is consumed, which is found to be the limiting reagent. This stops the formation of the normal large nanoparticles while their photo-ablation continues to make the small particles.},
	doi = {10.1039/B411488D},
	author = {Eustis, Susie and Krylova, G. and Eremenko, A. and Smirnova, N. and Schill, A. W. and El-Sayed, Mostafa A}
}
@article {821,
	title = {The Optically Detected Coherent Lattice Oscillations in Silver and Gold Monolayer Periodic Nanoprism Arrays:  The Effect of Interparticle Coupling},
	journal = {The Journal of Physical Chemistry B},
	volume = {109},
	year = {2005},
	note = {doi: 10.1021/jp0526647},
	month = {2005},
	pages = {18881 - 18888},
	publisher = {American Chemical Society},
	abstract = {Using femtosecond transient spectroscopy, we studied the optically detected laser-induced coherent phonon oscillation of monolayers of periodic arrays of prismatic-shaped silver and gold nanoparticles, assembled by using the technique of nanosphere lithography. In this method, the same size of polystyrene sphere and the same vacuum conditions are used. Under these circumstances, the gold nanoprisms formed are found to have sharper tips than the corresponding silver nanoprisms. For both gold and silver nanoparticles, the surface plasmon absorption maximum is found to depend linearly on size. The coherent lattice oscillation periods are also found to depend linearly on size. However, although the observed dependence for the silver nanoparticle is found to follow the calculated dependence of a single particle on size (based on a one-dimensional standing wave model), the gold nanoparticle deviates from this model, and the deviation is found to increase with the size of the nanoparticles. This deviation can be explained by considering interparticle coupling. A simple interparticle lattice oscillating dipolar coupling model of the dimer is found to qualitatively account for both the sign and the size dependence of the deviation. The absence of this deviation in the silver nanoparticle arrays is blamed on the weak interparticle coupling due to their rounded tips and the possibility of oxidation of their surfaces.Using femtosecond transient spectroscopy, we studied the optically detected laser-induced coherent phonon oscillation of monolayers of periodic arrays of prismatic-shaped silver and gold nanoparticles, assembled by using the technique of nanosphere lithography. In this method, the same size of polystyrene sphere and the same vacuum conditions are used. Under these circumstances, the gold nanoprisms formed are found to have sharper tips than the corresponding silver nanoprisms. For both gold and silver nanoparticles, the surface plasmon absorption maximum is found to depend linearly on size. The coherent lattice oscillation periods are also found to depend linearly on size. However, although the observed dependence for the silver nanoparticle is found to follow the calculated dependence of a single particle on size (based on a one-dimensional standing wave model), the gold nanoparticle deviates from this model, and the deviation is found to increase with the size of the nanoparticles. This deviation can be explained by considering interparticle coupling. A simple interparticle lattice oscillating dipolar coupling model of the dimer is found to qualitatively account for both the sign and the size dependence of the deviation. The absence of this deviation in the silver nanoparticle arrays is blamed on the weak interparticle coupling due to their rounded tips and the possibility of oxidation of their surfaces.},
	isbn = {1520-6106},
	doi = {10.1021/jp0526647},
	url = {http://dx.doi.org/10.1021/jp0526647},
	author = {Huang, Wenyu and Qian, Wei and El-Sayed, Mostafa A}
}
@proceedings {817,
	title = {Optically detected coherent picosecond lattice oscillations in two dimensional arrays of gold nanocrystals of different sizes and shapes induced by femtosecond laser pulses},
	volume = {5927},
	year = {2005},
	pages = {592701},
	abstract = {The nanosphere lithography (NSL) technique is used to make periodic gold array of prismatic nanoparticles. We use the femtosecond time resolved double beam transient optical detection to determine the coherent lattice oscillation in gold nanoparticles. Coherent lattice oscillation is compared on gold nanoparticles of different sizes and shapes. The effect of changing shape on the oscillation period was studied. Different environmental effects on the coherent lattice oscillation are eliminated by measuring the oscillation of the prismatic shape before and after we anneal it to spherical shape of the same number of atoms. A large change in the oscillation period is observed which agrees with the calculated period using different equations for the corresponding shapes.},
	doi = {10.1117/12.620501},
	url = {http://dx.doi.org/10.1117/12.620501},
	author = {Huang, Wenyu and Qian, Wei and El-Sayed, Mostafa A}
}
@article {1163,
	title = {Partial dehydration of the retinal binding pocket and proof for photochemical deprotonation of the retinal Schiff base in bicelle bacteriorhodopsin crystals},
	journal = {Photochemistry and Photobiology},
	volume = {81},
	number = {6},
	year = {2005},
	note = {Sanii, LS El-Sayed, MA},
	month = {Nov-Dec},
	pages = {1356-1360},
	abstract = {In bicelle bacteriorhodopsin (bcbR) crystals, the protein has a different structure from both native bacteriorhodopsin (bR) and in-cubo bR (cbR) crystals. Recently, we studied the ability of bcbR crystals to undergo the photocycle upon laser excitation, characterized by the appearance of the M intermediate by single crystal resonance Raman spectroscopy. Calculation of the M lifetime by flash photolysis experiments demonstrated that in our bchR crystals, the M rise time is much faster than in the native or cbR crystals, with a decay time that is much slower than these other two forms. Although it is now known that the bcbR crystals are capable of photochemical deprotonation, it is not known whether photochemical deprotonation is the only way to create the deprotonated Schiff base in the bcbR crystals. We measured both the visible and Raman spectra of crystals dried under ambient lighting and dried in the dark in order to determine whether the retinal Schiff base is able to thermally deprotonate in the dark. In addition, changes in the visible spectrum of single bcbR crystals under varying degrees of hydration and light exposure were examined to better understand the retinal binding environment.},
	isbn = {0031-8655},
	doi = {10.1562/2005-03-09-ra-458},
	author = {Sanii, L. S. and El-Sayed, Mostafa A}
}
@article {1170,
	title = {Photothermal reshaping of prismatic Au nanoparticles in periodic monolayer arrays by femtosecond laser pulses},
	journal = {Journal of Applied Physics},
	volume = {98},
	number = {11},
	year = {2005},
	note = {Huang, WY Qian, W El-Sayed, MA},
	month = {Dec},
	abstract = {Prismatic gold nanoparticles in the periodic monolayer arrays prepared with nanosphere lithography technique can be reshaped with femtosecond laser pulses at different powers and wavelengths. As the power density of 400 nm femtosecond laser increases, the prismatic particle tips begin to round and the overall particle shape changes from a prism to a sphere with a tripodal intermediate. The formation of the tip-rounded nanoprisms is probably due to the dewetting properties of gold on quartz surface and the low melting temperature at the tips. The formation of the tripodal nanoparticles is attributed to the inhomogeneous heating and lattice rearrangement of the as-deposited nanoparticles to a metastable state, which is more stable than the prismatic shape but less stable than the spherical shape. With 800 nm femtosecond laser irradiation, only tip-rounded nanoprisms are observed and no spherical nanoparticles are formed at the laser powers used. This is most likely due to the blueshift of the plasmon absorption band for the transformed particles, so that they cannot absorb the required energy to overcome the barrier to make the spherical shape. With 700 nm femtosecond laser irradiation, the tip-rounded and the tripodal nanoparticles are formed and few spherical particles are observed at the higher laser power density. From the results of this work, it is shown that by changing the wavelength and power density of the femtosecond laser, one can control the final shape of the particles formed from the original prismatic nanoparticles.},
	isbn = {0021-8979},
	doi = {10.1063/1.2132515},
	author = {Huang, Wenyu and Qian, Wei and El-Sayed, Mostafa A}
}
@article {1162,
	title = {The protonation-deprotonation kinetics of the protonated Schiff base in bicelle bacteriorhodopsin crystals},
	journal = {Biophysical Journal},
	volume = {89},
	number = {1},
	year = {2005},
	note = {Sanii, LS Schill, AW Moran, CE El-Sayed, MA},
	month = {Jul},
	pages = {444-451},
	abstract = {In the recently published x-ray crystal structure of the "bicelle" bacteriorhodopsin (bbR) crystal, the protein has quite a different structure from the native and the in cubo bacteriorhodopsin (cbR) crystal. Instead of packing in parallel trimers as do the native membrane and the cbR crystals, in the bbR crystal the protein packs as antiparallel monomers. To date, no functional studies have been performed, to our knowledge, to investigate if the photocycle is observed in this novel protein packing structure. In this study, both Raman and time-resolved transient absorption spectroscopy are used to both confirm the presence of the photocycle and investigate the deprotonation-reprotonation kinetics of the Schiff base proton in the bbR crystal. The observed rates of deprotonation and reprotonation processes of its Schiff base have been compared to those observed for native bR under the same conditions. Unlike the previously observed similarity of the rates of these processes for cbR crystals and those for native bacteriorhodopsin (bR), in bbR crystals the rate of deprotonation has increased by 300\%, and the rate of reprotonation has decreased by nearly 700\%. These results are discussed in light of the changes observed when native bR is delipidated or monomerized by detergents. Both the change of the hydrophobicity of the environment around the protonated Schiff base and Asp(85) and Asp(96) (which could change the pK(a) values of proton donor-acceptor pairs) and the water structure in the bbR crystal are offered as possible explanations for the different observations.},
	isbn = {0006-3495},
	doi = {10.1529/biophysj.105.059675},
	author = {Sanii, L. S. and Schill, A. W. and Moran, C. E. and El-Sayed, Mostafa A}
}
@article {820,
	title = {Raman Studies on the Interaction of the Reactants with the Platinum Nanoparticle Surface during the Nanocatalyzed Electron Transfer Reaction},
	journal = {The Journal of Physical Chemistry B},
	volume = {109},
	year = {2005},
	note = {doi: 10.1021/jp053526k},
	month = {2005},
	pages = {18460 - 18464},
	publisher = {American Chemical Society},
	abstract = {Raman studies are conducted to understand the specific interactions between the individual reactants and the platinum nanoparticle surface during the nanocatalyzed electron transfer reaction between hexacyanoferrate (III) ions and thiosulfate ions. When Pt nanoparticles are added to the thiosulfate ion solution, a shift in the symmetric SS stretching mode is observed compared to the frequency observed for the free thiosulfate ions in solution, suggesting that binding to the Pt nanoparticle surface occurs via the S- ion. It is also observed that there are no shifts in the symmetric and asymmetric OSO bending or SO stretching frequencies. This suggests that the thiosulfate ions do not bind to the nanoparticle surface via the O- ion. When platinum nanoparticles are added to the hexacyanoferrate(III) ion solution, evidence is found for both adsorbed hexacyanoferrate(III) ions and a platinum cyanide complex. For adsorbed hexacyanoferrate(III) ions, the CN stretching frequency is observed at 2101 cm-1 and the Fe?C stretching frequency is found at 368 cm-1. The observed CN stretching frequencies located at 2147 and 2167 cm-1 provide strong evidence that there is a Pt(CN)42- platinum cyanide complex formed. In addition, the Pt?C?N band is also observed at 2054 cm-1. These observed bands provide spectroscopic evidence that the hexacyanoferrate(III) ions dissolve by forming a complex with the surface platinum atoms of the nanoparticles. Raman spectra of the product mixtures are obtained after the completion of the reaction when carried out with higher reactant concentrations to observe the Raman spectra, but with a similar 10:1 ratio of thiosulfate to hexacyanoferrate(III) ions as used previously, with and without PVP?Pt nanoparticles at a correspondingly higher concentration. It is observed that there are no shifts in the characteristic Raman bands associated with hexacyanoferrate(II) ions and no evidence for the formation of adsorbed hexacyanoferrate(II) species or platinum cyanide complexes in the presence of the platinum nanoparticles. In addition, there is evidence for the shifted symmetric SS stretching mode, suggesting that some of the unreacted thiosulfate (present in large excess) is bound to the Pt nanoparticle surface. Thus, under the actual reaction conditions, the hexacyanoferrate(III) ions preferentially react with adsorbed thiosulfate ions to form the reaction products, and this supports the surface catalytic mechanism we proposed previously.Raman studies are conducted to understand the specific interactions between the individual reactants and the platinum nanoparticle surface during the nanocatalyzed electron transfer reaction between hexacyanoferrate (III) ions and thiosulfate ions. When Pt nanoparticles are added to the thiosulfate ion solution, a shift in the symmetric SS stretching mode is observed compared to the frequency observed for the free thiosulfate ions in solution, suggesting that binding to the Pt nanoparticle surface occurs via the S- ion. It is also observed that there are no shifts in the symmetric and asymmetric OSO bending or SO stretching frequencies. This suggests that the thiosulfate ions do not bind to the nanoparticle surface via the O- ion. When platinum nanoparticles are added to the hexacyanoferrate(III) ion solution, evidence is found for both adsorbed hexacyanoferrate(III) ions and a platinum cyanide complex. For adsorbed hexacyanoferrate(III) ions, the CN stretching frequency is observed at 2101 cm-1 and the Fe?C stretching frequency is found at 368 cm-1. The observed CN stretching frequencies located at 2147 and 2167 cm-1 provide strong evidence that there is a Pt(CN)42- platinum cyanide complex formed. In addition, the Pt?C?N band is also observed at 2054 cm-1. These observed bands provide spectroscopic evidence that the hexacyanoferrate(III) ions dissolve by forming a complex with the surface platinum atoms of the nanoparticles. Raman spectra of the product mixtures are obtained after the completion of the reaction when carried out with higher reactant concentrations to observe the Raman spectra, but with a similar 10:1 ratio of thiosulfate to hexacyanoferrate(III) ions as used previously, with and without PVP?Pt nanoparticles at a correspondingly higher concentration. It is observed that there are no shifts in the characteristic Raman bands associated with hexacyanoferrate(II) ions and no evidence for the formation of adsorbed hexacyanoferrate(II) species or platinum cyanide complexes in the presence of the platinum nanoparticles. In addition, there is evidence for the shifted symmetric SS stretching mode, suggesting that some of the unreacted thiosulfate (present in large excess) is bound to the Pt nanoparticle surface. Thus, under the actual reaction conditions, the hexacyanoferrate(III) ions preferentially react with adsorbed thiosulfate ions to form the reaction products, and this supports the surface catalytic mechanism we proposed previously.},
	isbn = {1520-6106},
	doi = {10.1021/jp053526k},
	url = {http://dx.doi.org/10.1021/jp053526k},
	author = {Narayanan, Radha and El-Sayed, Mostafa A}
}
@article {823,
	title = {Simulation of the Optical Absorption Spectra of Gold Nanorods as a Function of Their Aspect Ratio and the Effect of the Medium Dielectric Constant},
	journal = {The Journal of Physical Chemistry B},
	volume = {109},
	year = {2005},
	note = {doi: 10.1021/jp058091f},
	month = {2005},
	pages = {10531 - 10532},
	publisher = {American Chemical Society},
	isbn = {1520-6106},
	doi = {10.1021/jp058091f},
	url = {http://dx.doi.org/10.1021/jp058091f},
	author = {Link, Stephan and El-Sayed, Mostafa A}
}
@article {1173,
	title = {Surface plasmon resonance scattering and absorption of anti-EGFR antibody conjugated gold nanoparticles in cancer diagnostics: Applications in oral cancer},
	journal = {Nano Letters},
	volume = {5},
	number = {5},
	year = {2005},
	note = {El-Sayed, IH Huang, XH El-Sayed, MA},
	month = {May},
	pages = {829-834},
	abstract = {Gold nanoparticles with unique optical properties may be useful as biosensors in living whole cells. Using a simple and inexpensive technique, we recorded surface plasmon resonance (SPR) scattering images and SPR absorption spectra from both colloidal gold nanoparticles and from gold nanoparticles conjugated to monoclonal anti-epidermal growth factor receptor (anti-EGFR) antibodies after incubation in cell cultures with a nonmalignant epithelial cell line (HaCaT) and two malignant oral epithelial cell lines (HOC 313 clone 8 and HSC 3). Colloidal gold nanoparticles are found in dispersed and aggregated forms within the cell cytoplasm and provide anatomic labeling information, but their uptake is nonspecific for malignant cells. The anti-EGFR antibody conjugated nanoparticles specifically and homogeneously bind to the surface of the cancer type cells with 600\% greater affinity than to the noncancerous cells. This specific and homogeneous binding is found to give a relatively sharper SPR absorption band with a red shifted maximum compared to that observed when added to the noncancerous cells. These results suggest that SPR scattering imaging or SPR absorption spectroscopy generated from antibody conjugated gold nanoparticles can be useful in molecular biosensor techniques for the diagnosis and investigation of oral epithelial living cancer cells in vivo and in vitro.},
	keywords = {display},
	isbn = {1530-6984},
	doi = {10.1021/nl050074e},
	author = {El Sayed, I.H. and Huang, Xiaohua and El-Sayed, Mostafa A.}
}
@article {818,
	title = {Why gold nanoparticles are more precious than pretty gold: Noble metal surface plasmon resonance and its enhancement of the radiative and nonradiative properties of nanocrystals of different shapes},
	journal = {Chem. Soc. Rev.},
	volume = {35},
	year = {2005},
	pages = {209-217},
	publisher = {The Royal Society of Chemistry},
	abstract = {This tutorial review presents an introduction to the field of noble metal nanoparticles and their current applications. The origin of the surface plasmon resonance and synthesis procedures are described. A number of applications are presented that take advantage of the electromagnetic field enhancement of the radiative properties of noble metal nanoparticles resulting from the surface plasmon oscillations.},
	keywords = {display},
	doi = {10.1039/B514191E},
	author = {Eustis, Susie and El-Sayed, Mostafa A.}
}
@article {1181,
	title = {The assignment of the different infrared continuum absorbance changes observed in the 3000-1800-cm(-1) region during the bacteriorhodopsin photocycle},
	journal = {Biophysical Journal},
	volume = {87},
	number = {4},
	year = {2004},
	note = {Garczarek, F Wang, JP El-Sayed, MA Gerwert, K},
	month = {Oct},
	pages = {2676-2682},
	abstract = {The bleach continuum in the 1900-1800-cm(-1) region was reported during the photocycle of bacteriorhodopsin (bR) and was assigned to the dissociation of a polarizable proton chain during the proton release step. More recently, a broad band pass filter was used and additional infrared continua have been reported: a bleach at <2700 cm(-1), a bleach in the 2500-2150-cm(-1) region, and an absorptive behavior in the 2100-1800-cm(-1) region. To fully understand the importance of the hydrogen-bonded chains in the mechanism of the proton transport in bR, a detailed study is carried out here. Comparisons are made between the time-resolved Fourier transform infrared spectroscopy experiments on wild-type bR and its E204Q mutant (which has no early proton release), and between the changes in the continua observed in thermally or photothermally heated water (using visible light-absorbing dye) and those observed during the photocycle. The results strongly suggest that, except for the weak bleach in the 1900-1800-cm(-1) region and >2500 cm(-1), there are other infrared continua observed during the bR photocycle, which are inseparable from the changes in the absorption of the solvent water molecules that are photothermally excited via the nonradiative relaxation of the photoexcited retinal chromophore. A possible structure of the hydrogen-bonded system, giving rise to the observed bleach in the 1900-1800-cm(-1) region and the role of the polarizable proton in the proton transport is discussed.},
	isbn = {0006-3495},
	doi = {10.1529/biophysj.104.046433},
	author = {Garczarek, F. and Wang, Jianping and El-Sayed, Mostafa A and Gerwert, K.}
}
@article {1176,
	title = {Changing catalytic activity during colloidal platinum nanocatalysis due to shape changes: Electron-transfer reaction},
	journal = {Journal of the American Chemical Society},
	volume = {126},
	number = {23},
	year = {2004},
	note = {Narayanan, R El-Sayed, MA},
	month = {Jun},
	pages = {7194-7195},
	isbn = {0002-7863},
	doi = {10.1021/ja0486061},
	author = {Narayanan, Radha and El-Sayed, Mostafa A}
}
@article {1179,
	title = {Coherent vibrational oscillation in gold prismatic monolayer periodic nanoparticle arrays},
	journal = {Nano Letters},
	volume = {4},
	number = {9},
	year = {2004},
	note = {Huang, WY Qian, W El-Sayed, MA},
	month = {Sep},
	pages = {1741-1747},
	abstract = {We studied the ultrafast laser-induced coherent phonon oscillation in prismatic shaped gold nanoparticles assembled in monolayer periodic arrays by using the nanosphere lithographic technique. The amplitude and phase of the oscillation observed by ultrafast pump-probe transient spectroscopy is monitored as the wavelength of the dipolar surface plasmon absorption decreases. At a certain wavelength, the oscillation could not be observed. As the monitoring wavelength decreases further, the sign of the amplitude changes. From the wavelength at which the oscillation is not detected, the dependence of the absorption maxima on the size of the nanoparticles, the changes in the nanoparticle size are estimated during its oscillation. This large change in the size of the prismatic nanoparticle compared to the small change reported previously for the nanosphere oscillations is discussed.},
	isbn = {1530-6984},
	doi = {10.1021/nl048875p},
	author = {Huang, Wenyu and Qian, Wei and El-Sayed, Mostafa A}
}
@article {819,
	title = {Effect of Colloidal Catalysis on the Nanoparticle Size Distribution:  Dendrimer-Pd vs PVP-Pd Nanoparticles Catalyzing the Suzuki Coupling Reaction},
	journal = {The Journal of Physical Chemistry B},
	volume = {108},
	year = {2004},
	note = {doi: 10.1021/jp037169u},
	month = {2004},
	pages = {8572 - 8580},
	publisher = {American Chemical Society},
	abstract = {A comparison of the stability and catalytic activity of PAMAM?OH generation 4 dendrimer?Pd nanoparticles (1.3 {\textpm} 0.1 nm) with the previously studied PVP?Pd nanoparticles (2.1 {\textpm} 0.1 nm) in the Suzuki coupling reaction between phenylboronic acid and iodobenzene is conducted. After the first cycle, the average size of the PVP?Pd nanoparticles increases by 38\% and the dendrimer?Pd nanoparticles increases by 54\%. After the second cycle, the PVP?Pd nanoparticles decrease in size by 24\% whereas the dendrimer?Pd nanoparticles continue to increase in size by 35\%. The strong encapsulating action of the PAMAM?OH generation 4 dendrimer?Pd nanoparticles could make the rate of conversion to the full nanoparticle size slow, resulting in a large excess Pd metal atom concentration in solution, resulting in the continuous growth of the nanoparticles during the catalytic reaction. The effect of the individual reactants on the stability of the dendrimer?Pd nanoparticles has also been investigated and found to be similar to that observed for the PVP?Pd nanoparticles previously. It was found that the nanoparticle size growth occurs while refluxing in the presence of only the solvent, sodium acetate, or iodobenzene. However, the presence of phenylboronic acid is found to inhibit the particle growth, suggesting that it acts as a capping agent. Thus, the reaction mechanism must involve the adsorption of phenylboronic acid to the nanoparticle surface, which subsequently reacts with the iodobenzene in solution. This is similar to the mechanism found previously on PVP?Pd nanoparticles, suggesting that the mechanism is insensitive to the capping material used. The ratio of the yield of biphenyl formed in the second cycle to that in the first cycle is higher for the dendrimer?Pd nanoparticles catalyzed reaction than for the PVP?Pd nanoparticles. This could be due to the greater stability of the dendrimer?Pd nanoparticles and the increase in its size during the reaction. The larger PVP?Pd nanoparticles studied previously is believed to aggregate and precipitate out of solution during the second cycle. The presence of excess dendrimer is found to severely diminish the catalytic activity of the dendrimer?Pd nanoparticles and also diminishes the change in the Pd nanoparticle size during the catalysis.A comparison of the stability and catalytic activity of PAMAM?OH generation 4 dendrimer?Pd nanoparticles (1.3 {\textpm} 0.1 nm) with the previously studied PVP?Pd nanoparticles (2.1 {\textpm} 0.1 nm) in the Suzuki coupling reaction between phenylboronic acid and iodobenzene is conducted. After the first cycle, the average size of the PVP?Pd nanoparticles increases by 38\% and the dendrimer?Pd nanoparticles increases by 54\%. After the second cycle, the PVP?Pd nanoparticles decrease in size by 24\% whereas the dendrimer?Pd nanoparticles continue to increase in size by 35\%. The strong encapsulating action of the PAMAM?OH generation 4 dendrimer?Pd nanoparticles could make the rate of conversion to the full nanoparticle size slow, resulting in a large excess Pd metal atom concentration in solution, resulting in the continuous growth of the nanoparticles during the catalytic reaction. The effect of the individual reactants on the stability of the dendrimer?Pd nanoparticles has also been investigated and found to be similar to that observed for the PVP?Pd nanoparticles previously. It was found that the nanoparticle size growth occurs while refluxing in the presence of only the solvent, sodium acetate, or iodobenzene. However, the presence of phenylboronic acid is found to inhibit the particle growth, suggesting that it acts as a capping agent. Thus, the reaction mechanism must involve the adsorption of phenylboronic acid to the nanoparticle surface, which subsequently reacts with the iodobenzene in solution. This is similar to the mechanism found previously on PVP?Pd nanoparticles, suggesting that the mechanism is insensitive to the capping material used. The ratio of the yield of biphenyl formed in the second cycle to that in the first cycle is higher for the dendrimer?Pd nanoparticles catalyzed reaction than for the PVP?Pd nanoparticles. This could be due to the greater stability of the dendrimer?Pd nanoparticles and the increase in its size during the reaction. The larger PVP?Pd nanoparticles studied previously is believed to aggregate and precipitate out of solution during the second cycle. The presence of excess dendrimer is found to severely diminish the catalytic activity of the dendrimer?Pd nanoparticles and also diminishes the change in the Pd nanoparticle size during the catalysis.},
	isbn = {1520-6106},
	doi = {10.1021/jp037169u},
	url = {http://dx.doi.org/10.1021/jp037169u},
	author = {Narayanan, Radha and El-Sayed, Mostafa A}
}
@article {1177,
	title = {Effect of nanocatalysis in colloidal solution on the tetrahedral and cubic nanoparticle SHAPE: Electron-transfer reaction catalyzed by platinum nanoparticles},
	journal = {Journal of Physical Chemistry B},
	volume = {108},
	number = {18},
	year = {2004},
	note = {Narayanan, R El-Sayed, MA},
	month = {May},
	pages = {5726-5733},
	abstract = {The stability of tetrahedral and cubic platinum nanoparticles during the catalysis of the electron-transfer reaction between hexacyanoferrate (III) and thiosulfate ions in colloidal solution at room temperature was studied by using TEM and HRTEM. Before the reaction, the dominantly tetrahedral nanoparticles have a shape distribution of 55 +/- 4\% regular tetrahedral, 22 +/- 2\% distorted tetrahedral, and 23 +/- 2\% spherical nanoparticles, and the dominantly cubic nanoparticles have an initial shape distribution of 56 4\% regular cubes, 13 +/- 1\% distorted cubes, and 31 +/- 3\% truncated octahedral nanoparticles. The amount of tetrahedral nanoparticles decreases by 60 +/- 5\% after the first cycle and by 62 +/- 4\% after the second cycle of the reaction. In the case of cubic nanoparticles, the amount of cubic nanoparticles decreases by 39 +/- 5\% after the first cycle and by 66 +/- 5\% after the second cycle compared to before the reaction. After the first and second cycles of the reaction, there are a greater percentage of distorted tetrahedral and distorted cubic nanoparticles present. The rate of the dissolution of the surface Pt atoms is faster for the tetrahedral nanoparticles than for the cubic nanoparticles. This suggests that tetrahedral nanoparticles, with their sharp corners and edges, are more sensitive and more liable to shape changes during nanocatalysis. The presence of just hexacyanoferrate ions in the solution with the nanoparticles is found to increase the amount of distorted tetrahedral and distorted cubes present much more than during the reaction. The presence of only the thiosulfate ions does not seem to affect the size or shape distribution which might result from the capping ability of this anion and thus protects the nanoparticles.},
	isbn = {1520-6106},
	doi = {10.1021/jp0493780},
	author = {Narayanan, Radha and El-Sayed, Mostafa A}
}
@article {1180,
	title = {Eu3+ binding to europium-regenerated bacteriorhodopsin upon delipidation and monomerization},
	journal = {Febs Letters},
	volume = {562},
	number = {1-3},
	year = {2004},
	note = {Heyes, CD Reynolds, KB El-Sayed, MA},
	month = {Mar},
	pages = {207-210},
	abstract = {We have studied the effect of monomerization of the purple membrane lattice, as well as removal of 75\% of the lipids, on the binding properties of Eu3+ ions. We found that delipidation and monomerization do not cause the cations to lose their binding ability to the protein. This suggests that the three most strongly bound Eu3+ cations do not bind to the lipids, but directly bind to the protein. Furthermore, we found that delipidation actually causes a slight increase in the binding affinity. This is likely a result of reduced aggregation of europium-regenerated bacteriorhodopsin (bR) upon lipid removal causing more exposure of the binding sites to the Eu3+ cations. These results, taken with those from our previous publication [Heyes and El-Sayed, Biophys. J. 85 (2003) 426-434], might suggest that the cations remain bound upon delipidation of bR, but have no effect on the function. This is discussed with respect to the role of cations in the function of native bR. (C) 2004 Published by Elsevier B.V. on behalf of the Federation of European Biochemical Societies.},
	isbn = {0014-5793},
	doi = {10.1016/s0014-5793(04)00182-6},
	author = {Heyes, C D and Reynolds, K. B. and El-Sayed, Mostafa A}
}
@article {1183,
	title = {Model system for growing and quantifying Streptococcus pneumoniae biofilms in situ and in real time},
	journal = {Applied and Environmental Microbiology},
	volume = {70},
	number = {8},
	year = {2004},
	note = {Donlan, RM Piede, JA Heyes, CD Sanii, L Murga, R Edmonds, P El-Sayed, I El-Sayed, MA},
	month = {Aug},
	pages = {4980-4988},
	abstract = {Streptococcus pneumoniae forms biofilms, but little is known about its extracellular polymeric substances (EPS) or the kinetics of biofilm formation. A system was developed to enable the simultaneous measurement of cells and the EPS of biofilm-associated S. pneumoniae in situ over time. A biofilm reactor containing germanium coupons was interfaced to an attenuated total reflectance (ATR) germanium cell of a Fourier transform infrared (FTIR) laser spectrometer. Biofilm-associated cells were recovered from the coupons and quantified by total and viable cell count methods. ATR-FTIR spectroscopy of biofilms formed on the germanium internal reflection element (IRE) of the ATR cell provided a continuous spectrum of biofilm protein and polysaccharide (a measure of the EPS). Staining of the biofilms on the IRE surface with specific fluorescent probes provided confirmatory evidence for the biofilm structure and the presence of biofilm polysaccharides. Biofilm protein and polysaccharides were detected within hours after inoculation and continued to increase for the next 141 h. The polysaccharide band increased at a substantially higher rate than did the protein band, demonstrating increasing coverage of the IRE surface with biofilm polysaccharides. The biofilm total cell counts on germanium coupons stabilized after 21 h, at approximately 10(5) cells per cm(2), while viable counts decreased as the biofilm aged. This system is unique in its ability to detect and quantify biofilm-associated cells and EPS of S. pneumoniae over time by using multiple, corroborative techniques. This approach could prove useful for the study of biofilm processes of this or other microorganisms of clinical or industrial relevance.},
	isbn = {0099-2240},
	doi = {10.1128/aem.70.8.4980-4988.2004},
	author = {Donlan, R. M. and Piede, J. A. and Heyes, C D and Sanii, L. S. and Murga, R. and Edmonds, P. and El Sayed, I.H. and El-Sayed, Mostafa A}
}
@article {840,
	title = {Picosecond Self-Induced Thermal Lensing from Colloidal Silver Nanodisks},
	journal = {The Journal of Physical Chemistry B},
	volume = {108},
	year = {2004},
	note = {doi: 10.1021/jp049943z},
	month = {2004},
	pages = {5230 - 5234},
	publisher = {American Chemical Society},
	abstract = {The optical and nonradiative relaxation dynamics of 5 nm thick silver nanodisks with a 25 nm diameter have been investigated in an organic solvent by continuous wave (cw) and femtosecond pump?probe time-resolved spectroscopies. Several surface plasmon absorption bands are observed due to the disk shape of these particles. In the time-resolved experiments, the time dependence of the bleach resulting from femtosecond pulsed excitation is studied. On the 1?3 ps time scale, a decay resulting from electron?phonon relaxation is observed. On a longer time scale (>20 ps), a rise rather than a further decay of the bleach intensity is observed. This is shown to result from the formation of a thermal lens due to the induced thermal gradients produced from heating the organic solvent by the phonon?phonon relaxation processes of the photoexcited nanodisks.The optical and nonradiative relaxation dynamics of 5 nm thick silver nanodisks with a 25 nm diameter have been investigated in an organic solvent by continuous wave (cw) and femtosecond pump?probe time-resolved spectroscopies. Several surface plasmon absorption bands are observed due to the disk shape of these particles. In the time-resolved experiments, the time dependence of the bleach resulting from femtosecond pulsed excitation is studied. On the 1?3 ps time scale, a decay resulting from electron?phonon relaxation is observed. On a longer time scale (>20 ps), a rise rather than a further decay of the bleach intensity is observed. This is shown to result from the formation of a thermal lens due to the induced thermal gradients produced from heating the organic solvent by the phonon?phonon relaxation processes of the photoexcited nanodisks.},
	isbn = {1520-6106},
	doi = {10.1021/jp049943z},
	url = {http://dx.doi.org/10.1021/jp049943z},
	author = {Maillard, Mathieu and Pileni, Marie-Paule and Link, Stephan and El-Sayed, Mostafa A}
}
@article {1178,
	title = {Picosecond self-induced thermal lensing from colloidal silver nanodisks},
	journal = {Journal of Physical Chemistry B},
	volume = {108},
	number = {17},
	year = {2004},
	note = {Maillard, M Pileni, MP Link, S El-Sayed, MA},
	month = {Apr},
	pages = {5230-5234},
	abstract = {The optical and nonradiative relaxation dynamics of 5 unit thick silver nanodisks with a 25 nm diameter have been investigated in an organic solvent by continuous wave (cw) and femtosecond pump-probe time-resolved spectroscopies. Several surface plasmon absorption bands are observed due to the disk shape of these particles. In the time-resolved experiments, the time dependence of the bleach resulting from femtosecond pulsed excitation is studied. On the 1-3 ps time scale, a decay resulting from electron-phonon relaxation is observed. On a longer time scale (>20 ps), a rise father than a further decay of the bleach intensity is observed. This is shown to result from the formation of a thermal lens due to the induced thermal gradients produced from heating the organic solvent by the phonon-phonon relaxation processes of the photoexcited nanodisks.},
	isbn = {1520-6106},
	doi = {10.1021/jp049943z},
	author = {Maillard, Mathieu and Pileni, Marie-Paule and Link, Stephan and El-Sayed, Mostafa A}
}
@article {838,
	title = {Propylene hydrogenation over cubic Pt nanoparticles deposited on alumina},
	journal = {BULLETIN-KOREAN CHEMICAL SOCIETY},
	volume = {25},
	year = {2004},
	pages = {843-846},
	publisher = {Korean Chemical Society},
	abstract = {Pt nanoparticles loaded on alumina through an impregnation at room temperature was prepared using K2PtCl4 and acrylic acid as capping material. Transmission electron microscopy showed that the deposited Pt particles indicate ca. 80\% cubic shapes with a narrow distribution of 8-10 nm in size. Propylene hydrogenation over the catalyst has been carried out to evaluate their catalytic performance by the values of activation energy. It is determined from the initial rate, reaction order, and rate constant and is found to be 9.7 {\textpm} 0.5 kcal/mol. This value has been discussed by comparing to those of encapsulated- and truncated octahedral Pt nanoparticles deposited on alumina, respectively, to study influence of the particle size and shape, and capping material used
on the activation energy.},
	isbn = {0253-2964},
	url = {http://www.journal.kcsnet.or.kr/main/j_search/j_abstract_view.htm?code=B040616\&qpage=j_search\&spage=b_bkcs\&dpage=ar},
	author = {Yoo, J. W. and Lee, S.M. and Kim, H.T. and El-Sayed, Mostafa A}
}
@article {839,
	title = {Shape control of platinum nanoparticles by using different capping organic materials},
	journal = {BULLETIN-KOREAN CHEMICAL SOCIETY},
	volume = {25},
	year = {2004},
	pages = {395},
	abstract = {No Abstract},
	keywords = {Cube, Nanoparticle, Platinum, Transmission electron microscopy, Truncated octahedra},
	url = {http://newjournal.kcsnet.or.kr/main/j_search/j_abstract_view.htm?code=B040315\&qpage=j_search\&spage=b_bkcs\&dpage=ar},
	author = {Yoo, J. W. and Lee, S.M. and Kim, H.T. and El-Sayed, Mostafa A}
}
@article {1175,
	title = {Shape-dependent catalytic activity of platinum nanoparticles in colloidal solution},
	journal = {Nano Letters},
	volume = {4},
	number = {7},
	year = {2004},
	note = {Narayanan, R El-Sayed, MA},
	month = {Jul},
	pages = {1343-1348},
	abstract = {The activation energies and the average rate constants are determined in the 298 K-318 K temperature range for the early stages of the nanocatalytic reaction between hexacyanoferrate (111) and thiosulfate ions using 4.8 +/- 0.1 nm tetrahedral, 7.1 +/- 0.2 nm cubic, and 4.9 +/- 0.1 nm "near spherical" nanocrystals. These kinetic parameters are found to correlate with the calculated fraction of surface atoms located on the corners and edges in each size and shape.},
	isbn = {1530-6984},
	doi = {10.1021/nl0495256},
	author = {Narayanan, Radha and El-Sayed, Mostafa A}
}
@article {1182,
	title = {Small is different: Shape-, size-, and composition-dependent properties of some colloidal semiconductor nanocrystals},
	journal = {Accounts of Chemical Research},
	volume = {37},
	number = {5},
	year = {2004},
	note = {El-Sayed, MA},
	month = {May},
	pages = {326-333},
	abstract = {As the size of material becomes equal to or falls below the nanometer length scale that characterizes the motion of its electrons and thus its properties, the latter become sensitive not only to the size but also to the shape and composition of the particles. In this Account, we describe the changes of some interesting properties in different colloidal semiconductor nanoparticles, such as the electronic relaxation rates as spherical nanoparticles change to nanorods, and the changes in the structure or size of very small nanoparticles upon adsorbing strongly bound molecules. We have also determined and explained the difference in the interfacial crossing rates of electrons and holes in a composite nanostructure.},
	isbn = {0001-4842},
	doi = {10.1021/ar020204f},
	author = {El-Sayed, Mostafa A}
}
@article {1174,
	title = {Wavelength-dependent hot electron relaxation in PVP capped CdS/HgS/CdS quantum dot quantum well nanocrystals},
	journal = {Journal of Physical Chemistry B},
	volume = {108},
	number = {36},
	year = {2004},
	note = {Schill, AW El-Sayed, MA},
	month = {Sep},
	pages = {13619-13625},
	abstract = {Subpicosecond pump-probe transient absorption spectroscopy has been used to examine the probe wavelength-dependent kinetics of PVP capped CdS/HgS/CdS quantum dot quantum well nanoparticles. Using 398- and 520-nm excitations, the relaxation of the excited hot electrons above the band gap state is characterized by both rapid electronic nonradiative relaxation and slower thermal relaxation processes. The wavelength dependence of both the fast rise and fast decay of the transient bleach is discussed in terms of electronic relaxation processes involving mixed CdS/HgS states at short probe wavelengths or pure HgS states at long probe wavelengths. The slow decay of the transient bleach is discussed in terms of a thermal relaxation process leading to the dissipation of heat from the hot nanoparticle lattice to the surrounding medium.},
	isbn = {1520-6106},
	doi = {10.1021/jp047832u},
	author = {Schill, A. W. and El-Sayed, Mostafa A}
}
@article {1186,
	title = {Effect of catalysis on the stability of metallic nanoparticles: Suzuki reaction catalyzed by PVP-palladium nanoparticles},
	journal = {Journal of the American Chemical Society},
	volume = {125},
	number = {27},
	year = {2003},
	note = {Narayanan, R El-Sayed, MA},
	month = {Jul},
	pages = {8340-8347},
	abstract = {The small size of nanoparticles makes them attractive in catalysis due to their large surface-to-volume ratio. However, being small raises questions about their stability in the harsh chemical environment in which these nanoparticles find themselves during their catalytic function. In the present work, we studied the Suzuki reaction between phenylboronic acid and iodobenzene catalyzed by PVP-Pd nanoparticles to investigate the effect of catalysis, recycling, and the different individual chemicals on the stability and catalytic activity of the nanoparticles during this harsh reaction. The stability of the nanoparticles to the different perturbations is assessed using TEM, and the changes in the catalytic activity are assessed using HPLC analysis of the product yield. It was found that the process of refluxing the nanoparticles for 12 h during the Suzuki catalytic reaction increases the average size and the width of the distribution of the nanoparticles. This was attributed to Ostwald ripening in which the small nanoparticles dissolve to form larger nanoparticles. The kinetics of the change in the nanoparticle size during the 12 h period show that the nanoparticles increase in size during the beginning of the reaction and level off toward the end of the first cycle. When the nanoparticles are recycled for the second cycle, the average size decreases. This could be due to the larger nanoparticles aggregating and precipitating out of solution. This process could also explain the observed loss of the catalytic efficiency of the nanoparticles during the second cycle. It is also found that the addition of biphenyl to the reaction mixture results in it poisoning the active sites and giving rise to a low product yield. The addition of excess PVP stabilizer to the reaction mixture seems to lead to the stability of the nanoparticle surface and size, perhaps due to the inhibition of the Ostwald ripening process. This also decreases the catalytic efficiency of the nanoparticles due to capping of the nanoparticle surface. The addition of phenylboronic acid is found to lead to the stability of the size distribution as it binds to the particle surface through the O- of the OH group and acts as a stabilizer. Iodobenzene is found to have no effect and thus probably does not bind strongly to the surface during the catalytic process. These two results might have an implication on the catalytic mechanism of this reaction.},
	isbn = {0002-7863},
	doi = {10.1021/ja035044x},
	author = {Narayanan, Radha and El-Sayed, Mostafa A}
}
@article {1185,
	title = {Effect of catalytic activity on the metallic nanoparticle size distribution: Electron-transfer reaction between Fe(CN)(6) and thiosulfate ions catalyzed by PVP-platinum nanoparticles},
	journal = {Journal of Physical Chemistry B},
	volume = {107},
	number = {45},
	year = {2003},
	note = {Narayanan, R El-Sayed, MA},
	month = {Nov},
	pages = {12416-12424},
	abstract = {The electron-transfer reaction between hexacyanoferrate(III) ions and thiosulfate ions is known to be catalyzed by platinum nanoparticles. In the present study, the stability and catalytic activity of the PVP-Pt nanoparticle during its catalytic function for this electron-transfer reaction is studied. The stability of the nanoparticles after various perturbations was assessed using TEM, and the kinetics of the reaction was followed using absorption spectroscopy. The studies were conducted on four different concentrations of PVP-Pt nanoparticles. It was found that the average size and width of the PVP-Pt nanoparticles decrease slightly after the first and second cycles of the electron-transfer reaction. The size and size distribution width do not change in the presence of only the thiosulfate reactant, whereas the presence of only the hexacyanoferrate reactant results in a reduction of the nanoparticle size. The reduction in the nanoparticle size in the presence of hexacyanoferrate(HI) ions is proposed to result from the dissolution of surface Pt atoms through complexation with the strong cyanide ligand. Thiosulfate ions bind to the nanoparticle surface and act as a capping material, resulting in the stability of the nanoparticles. Judging from these observations, it is possible that the mechanism of this catalytic reaction involves the thiosulfate ions binding to the free sites on the surface of the nanoparticles, followed by reaction with hexacyanoferrate ions approaching the nanoparticle surface from the solution. Conducting the reaction with the nanoparticles preexposed to thiosulfate results in very little change in the centers and widths of the size distributions of the nanoparticles, thus suggesting that thiosulfate ions bind to the nanoparticle surface and inhibit desorption of Pt atoms by hexacyanoferrate(III) ions. The kinetics of the electron-transfer reaction during the first and second cycles is similar. The activation energy of the nanoparticle catalytic reaction is found to decrease linearly with increasing nanoparticle concentration during both the first and second cycles. If increasing the nanoparticle concentration leads to more aggregation, then these results suggest that the aggregated Pt has greater catalytic activity than the individual nanoparticles.},
	isbn = {1520-6106},
	doi = {10.1021/jp035647v},
	author = {Narayanan, Radha and El-Sayed, Mostafa A}
}
@article {846,
	title = {FTIR study of the adsorption of the capping material to different platinum nanoparticle shapes},
	journal = {The Journal of Physical Chemistry A},
	volume = {107},
	year = {2003},
	pages = {8371-8375},
	publisher = {ACS Publications},
	abstract = {FTIR spectroscopy has been used to study the binding geometry of polyacrylate capping material on cubic and tetrahedral platinum nanoparticles. It is proposed that the capping material forms an ester-like linkage to the Pt surface on the tetrahedral shapes through the hydroxyl oxygen atom of the carboxylic acid moiety of the polyacrylate (linear adsorption configuration). On the cubic particle the adsorption is through both of the carboxylic oxygen atoms (bridge adsorption configuration). These shaped nanoparticles are synthesized by changing the starting ratio of the capping material to that of the Pt salt. The results are discussed in terms of the effect of changing the concentration of the polyacrylate capping material on the mode of bonding to the surface. This might be a factor in determining the final shape formed.},
	isbn = {1089-5639},
	doi = {10.1021/jp0300694},
	url = {http://dx.doi.org/10.1021/jp0300694},
	author = {Petroski, J. M. and El-Sayed, Mostafa A}
}
@article {1187,
	title = {Medium effect on the electron cooling dynamics in gold nanorods and truncated tetrahedra},
	journal = {Advanced Materials},
	volume = {15},
	number = {5},
	year = {2003},
	note = {Link, S Hathcock, DJ Nikoobakht, B El-Sayed, MA},
	month = {Mar},
	pages = {393-+},
	abstract = {A study on the electron relaxation dynamics and thermal cooling of colloidal gold nanoparticles (see Figure) in air and water finds that the local energy exchange with the surrounding medium occurs on the picosecond time scale, comparable with the electron-phonon relaxation, while a slow heat dissipation by water ensures that the particles remain heated for hundreds of picoseconds.},
	isbn = {0935-9648},
	doi = {10.1002/adma.200390088},
	author = {Link, Stephan and Hathcock, D. J. and Nikoobakht, Babak and El-Sayed, Mostafa A}
}
@article {848,
	title = {Optical Properties and Ultrafast Dynamics of Metalic Naocrystals},
	journal = {Annual Review of Physical Chemistry },
	volume = {54},
	year = {2003},
	note = {doi: 10.1146/annurev.physchem.54.011002.103759},
	month = {2003},
	pages = {331 - 366},
	publisher = {Annual Reviews},
	abstract = {? Abstract? Noble metal particles have long fascinated scientists because of their intense color, which led to their application in stained glass windows as early as the Middle Ages. The recent resurrection of colloidal and cluster chemistry has brought about the strive for new materials that allow a bottoms-up approach of building improved and new devices with nanoparticles or artificial atoms. In this review, we discuss some of the properties of individual and some assembled metallic nanoparticles with a focus on their interaction with cw and pulsed laser light of different energies. The potential application of the plasmon resonance as sensors is discussed.? Abstract? Noble metal particles have long fascinated scientists because of their intense color, which led to their application in stained glass windows as early as the Middle Ages. The recent resurrection of colloidal and cluster chemistry has brought about the strive for new materials that allow a bottoms-up approach of building improved and new devices with nanoparticles or artificial atoms. In this review, we discuss some of the properties of individual and some assembled metallic nanoparticles with a focus on their interaction with cw and pulsed laser light of different energies. The potential application of the plasmon resonance as sensors is discussed.},
	isbn = {0066-426X},
	url = {http://dx.doi.org/10.1146/annurev.physchem.54.011002.103759},
	author = {Link, Stephan and El-Sayed, Mostafa A}
}
@article {847,
	title = {Preparation and Growth Mechanism of Gold Nanorods (NRs) Using Seed-Mediated Growth Method},
	journal = {Chemistry of Materials},
	volume = {15},
	year = {2003},
	note = {doi: 10.1021/cm020732l},
	month = {2003},
	pages = {1957 - 1962},
	publisher = {American Chemical Society},
	isbn = {0897-4756},
	url = {http://dx.doi.org/10.1021/cm020732l},
	author = {Nikoobakht, Babak and El-Sayed, Mostafa A}
}
@article {1184,
	title = {Propene hydrogenation over truncated octahedral Pt nanoparticles supported on alumina},
	journal = {Journal of Catalysis},
	volume = {214},
	number = {1},
	year = {2003},
	note = {Yoo, JW Hathcock, DJ El-Sayed, MA},
	month = {Feb},
	pages = {1-7},
	abstract = {Colloidal Pt nanoparticles synthesized by a 1 : 5 concentration ratio of K2PtCl4 to polyacrylate were loaded on nanoporous alumina using the impregnation method at room temperature. The deposited Pt particles, present on the external surfaces of the support, were characterized by transmission electron microscopy, which indicated predominantly truncated octahedral (TO) shapes with a mean diameter of 10 nm. Their catalytic performance in the hydrogenation of propene at 30-80 degreesC was studied as a test reaction. The initial rate, reaction order, rate constant, activation energy, and turnover frequency were determined. The activation energy was found to be 8.4 +/- 0.2 kcal/mol, which is slightly lower than results reported for other platinum systems (10-14 kcal/mol). The TO platinum nanoparticles have atom-high surface steps, ledges, and kinks, and these atomic-scale fine structures are expected to decrease the activation energy. The reactivity of the surface atoms in this nanoparticle is so high that above 50 degreesC side reactions leading to complete surface poisoning take place within a few minutes. The effect of the polymer concentration of the polyacrylate-capped TO Pt/Al2O3 on the hydrogenation catalytic activity was also investigated. (C) 2003 Elsevier Science (USA). All rights reserved.},
	isbn = {0021-9517},
	doi = {10.1016/s0021-9517(02)00136-7},
	author = {Yoo, J. W. and Hathcock, D. J. and El-Sayed, Mostafa A}
}
@article {841,
	title = {Proton transfer reactions in native and deionized bacteriorhodopsin upon delipidation and monomerization},
	journal = {Biophysical journal},
	volume = {85},
	year = {2003},
	pages = {426-434},
	publisher = {Elsevier},
	abstract = {We have investigated the role of the native lipids on bacteriorhodopsin (bR) proton transfer and their connection with the cation-binding role. We observe that both the efficiency of M formation and the kinetics of M rise and decay depend on the lipids and lattice but, as the lipids are removed, the cation binding is a much less important factor for the proton pumping function. Upon 75\% delipidation using 3-[(cholamidopropyl)dimethylammonio]-propanesulfonate (CHAPS), the M formation and decay kinetics are much slower than the native, and the efficiency of M formation is \~{}30\%{\textendash}40\% that of the native. Upon monomerization of bR by Trition X-100, the efficiency of M recovers close to that of the native (depending on pH), M formation is \~{}10 times faster, and M decay kinetics are comparable to native at pH 7. The same results on the M intermediate are observed if deionized blue bR (deI bbR) is treated with these detergents (with or without pH buffers present), even though deionized blue bR containing all the lipids has no photocycle. This suggests that the cation(s) has a role in native bR that is different than in delipidated or monomerized bR, even so far as to suggest that the cation(s) becomes unimportant to the function as the lipids are removed.},
	isbn = {0006-3495},
	doi = {10.1016/S0006-3495(03)74487-7},
	url = {http://dx.doi.org/10.1016/S0006-3495(03)74487-7},
	author = {Heyes, C D and El-Sayed, Mostafa A}
}
@article {845,
	title = {Relative enhancement of ultrafast emission in gold nanorods},
	journal = {The Journal of Physical Chemistry B},
	volume = {107},
	year = {2003},
	pages = {3101-3104},
	publisher = {ACS Publications},
	abstract = {Time-resolved fluorescence spectroscopy has been employed to probe the ultrafast emission observed in gold nanospheres and nanorods. The decay of the emission was found to be <=50 fs. The ultrafast emission from nanorods has been directly compared to that for nanospheres and the dispersion of the relative local field enhancement factor was obtained and compared with calculations. Measurements with both visible and ultraviolet excitations have been analyzed. These results give the first observation and analysis of the mechanism for the local field-enhanced ultrafast emission in gold nanorods and nanospheres.},
	isbn = {1520-6106},
	doi = {10.1021/jp0341265},
	url = {http://dx.doi.org/10.1021/jp0341265},
	author = {Varnavski, O. P. and Mohamed, MB and El-Sayed, Mostafa A and Goodson III, T.}
}
@article {844,
	title = {Surface-Enhanced Raman Scattering Studies on Aggregated Gold Nanorods},
	journal = {The Journal of Physical Chemistry AThe Journal of Physical Chemistry A},
	volume = {107},
	year = {2003},
	note = {doi: 10.1021/jp026770+},
	month = {2003},
	pages = {3372 - 3378},
	publisher = {American Chemical Society},
	abstract = {Surface-enhanced Raman scattering (SERS) of adsorbed molecules on gold nanorods (NRs) with dimensions of 10 nm ? 27 nm was studied on silica surface with low to high surface coverage of NRs. The study was carried out to investigate both the dependence of the SERS intensity on the number of NRs and the NRs spacing on the silica surface. SERS of adsorbed molecules such as 2-aminothiophenol (2-ATP) and the capping molecules (hexadecyltrimethylammonium bromide) was studied on these surfaces using a near-IR laser excitation source (1064 nm). To produce silica surfaces covered with NRs, two approaches were used. In the first approach, monodispersed NRs gradually deposited from solution to silica surface and their number was increased by increasing the deposition time. In the second one, the NRs were first aggregated in solution and then deposited on the surface. Although using the first approach it was possible to prepare surfaces with high NR surface coverage, SERS intensity was found to be stronger for adsorbed molecules on surfaces covered with aggregated NRs. The observed increase in the SERS intensity in the case of aggregation was attributed to the enhancement of the electric field between the particles in the aggregates. It is shown that aggregated NRs in comparison with aggregated nanospheres (NSs) have stronger SERS enhancement under similar experimental conditions. In this comparison, some of the enhanced vibrational bands of 2-ATP on aggregated NRs are weakly enhanced or absent on aggregated NSs. Monitoring the SERS intensity of adsorbed 2-ATP versus its exposure time to the aggregated NRs shows that the SERS intensity of the adsorbed molecules reaches saturation, whereas the peak intensities of the capping molecules remain unchanged. The intensity saturation was discussed in terms of factors such as the saturation of the SERS active sites for 2-ATP on the gold surface and the partial damping of the plasmon band due to the stronger interaction of the adsorbate molecules with the metal surface.Surface-enhanced Raman scattering (SERS) of adsorbed molecules on gold nanorods (NRs) with dimensions of 10 nm ? 27 nm was studied on silica surface with low to high surface coverage of NRs. The study was carried out to investigate both the dependence of the SERS intensity on the number of NRs and the NRs spacing on the silica surface. SERS of adsorbed molecules such as 2-aminothiophenol (2-ATP) and the capping molecules (hexadecyltrimethylammonium bromide) was studied on these surfaces using a near-IR laser excitation source (1064 nm). To produce silica surfaces covered with NRs, two approaches were used. In the first approach, monodispersed NRs gradually deposited from solution to silica surface and their number was increased by increasing the deposition time. In the second one, the NRs were first aggregated in solution and then deposited on the surface. Although using the first approach it was possible to prepare surfaces with high NR surface coverage, SERS intensity was found to be stronger for adsorbed molecules on surfaces covered with aggregated NRs. The observed increase in the SERS intensity in the case of aggregation was attributed to the enhancement of the electric field between the particles in the aggregates. It is shown that aggregated NRs in comparison with aggregated nanospheres (NSs) have stronger SERS enhancement under similar experimental conditions. In this comparison, some of the enhanced vibrational bands of 2-ATP on aggregated NRs are weakly enhanced or absent on aggregated NSs. Monitoring the SERS intensity of adsorbed 2-ATP versus its exposure time to the aggregated NRs shows that the SERS intensity of the adsorbed molecules reaches saturation, whereas the peak intensities of the capping molecules remain unchanged. The intensity saturation was discussed in terms of factors such as the saturation of the SERS active sites for 2-ATP on the gold surface and the partial damping of the plasmon band due to the stronger interaction of the adsorbate molecules with the metal surface.},
	isbn = {1089-5639},
	doi = {10.1021/jp026770+},
	url = {http://dx.doi.org/10.1021/jp026770+},
	author = {Nikoobakht, Babak and El-Sayed, Mostafa A}
}
@article {1188,
	title = {Thermal properties of bacteriorhodopsin},
	journal = {Journal of Physical Chemistry B},
	volume = {107},
	number = {44},
	year = {2003},
	note = {Heyes, CD El-Sayed, MA},
	month = {Nov},
	pages = {12045-12053},
	abstract = {In this Feature Article we review the effects of various parameters on the structure and thermal stability of one of the most widely studied membrane proteins, bacteriorhodopsin. This protein has recently been crystallized and its high-resolution structure elucidated to 1.55 Angstrom. This information has proved invaluable in understanding its proton-pumping mechanism. However, the question of why bacteriorhodopsin is so stable over a wide range of conditions, and which factors contribute to this stability, is still largely unanswered. Spectroscopic and calorimetric experiments provide information on the thermodynamics, kinetics and structural changes upon unfolding and refolding the protein under various environmental perturbations. FT-IR spectroscopy has been particularly useful in determining the changes in secondary structure upon heating through its thermal transitions after changing pH and cations, removing and adding lipids and detergents, retinal reduction and removal, and site-directed mutagenesis. These experiments are reviewed, and the information that they have afforded have been brought together to try to understand how nature has controlled the conditions of bR to make it one of the most stable proteins known.},
	isbn = {1520-6106},
	doi = {10.1021/jp035327b},
	author = {Heyes, C D and El-Sayed, Mostafa A}
}
@article {1189,
	title = {Why is the thermalization of excited electrons in semiconductor nanoparticles so rapid? Studies on CdSe nanoparticles},
	journal = {Chemical Physics Letters},
	volume = {373},
	number = {3-4},
	year = {2003},
	note = {Darugar, Q Landes, C Link, S Schill, A El-Sayed, MA},
	month = {May},
	pages = {284-291},
	abstract = {Quantum confinement of electronic motion in semiconductor nanoparticles leads to quantization of its band continua of the bulk. The relaxation between the resulting quantized levels by electron phonon coupling was expected, but not found, to be slow due to the small phonon frequencies (phonon bottleneck). Studying the electronic relaxation from the band gap and a higher excited state in CdSe dots and rods under different perturbations suggest the importance of coupling the excited electron to the surface. The surface species act as an efficient heat bath or as electron trapping sites in the linear or nonlinear (Auger) relaxation processes. (C) 2003 Elsevier Science B.V. All rights reserved.},
	isbn = {0009-2614},
	doi = {10.1016/s0009-2614(03)00213-6},
	author = {Darugar, Q. and Landes, Christy F. and Link, Stephan and Schill, A. W. and El-Sayed, Mostafa A}
}
@article {1190,
	title = {Characterization of pt nanoparticles encapsulated in Al2O3 and their catalytic efficiency in propene hydrogenation},
	journal = {Journal of Physical Chemistry A},
	volume = {106},
	number = {10},
	year = {2002},
	note = {Yoo, JW Hathcock, D El-Sayed, MA},
	month = {Mar},
	pages = {2049-2054},
	abstract = {Pt nanoparticles supported in nanoporous Al2O3 catalyst are prepared by reduction of K2PtCl4 solution using 112 in the presence of Al2O3 and poly(acrylic acid) as capping; material. After thorough washing with water to remove Pt nanoparticles located on the external surface of the Al2O3 and drying at 70 degreesC for 12 h, they were used in propene hydrogenation to evaluate catalytic activity as measured by the value of the activation energy in the temperature range between 30 and 90 degreesC. The Pt nanoparticles are characterized by using transmission electron microscopy (TEM). The particles in Pt/Al2O3 are found to be encapsulated and uniformly dispersed inside the Al2O3; however, the size and shapes are not clearly seen. After extraction of the Pt nanoparticles from the Al2O3 channels by using an ethanol-diluted HF solution, various shapes such as truncated octahedral, cubic, tetrahedral, and spherical with a size around 5 nm are observed. The encapsulated particles have various shapes but are smaller in size than those prepared in K2PtCl4 solution with polyacrylate in the absence of Al2O3. Using FT-IR studies, the capping material initially used in Pt/Al2O3 is not found in the Al2O3 channels. This might be due to the fact that the polymer (average MW 2100) is too large to be accommodated within the Al2O3 pores. The nanopores of Al2O3 have several roles in the synthesis of these nanoparticles. It allows for uniform dispersion and encapsulation of Pt nanoparticles. It controls the Pt sizes with narrow distribution that is determined by the pore dimension (5.8 nm). It protects against metal particle aggregation and produces various shapes even in the absence of the capping material. Using these Pt nanoparticles, the catalysis of hydrogenation of propene gas was studied. The initial rates, reaction order, rate constants, and activation energy for the hydrogenation are determined by use of mass spectrometric techniques. The activation energy is found to be 5.7 kcal/mol, which is about one-half that previously reported for catalysis by Pt metal deposited in SiO2 and TiO2 synthesized by using H2PtCl6 and Pt(allyl)(2) by impregnation method.},
	isbn = {1089-5639},
	doi = {10.1021/jp0121318},
	author = {Yoo, J. W. and Hathcock, D. J. and El-Sayed, Mostafa A}
}
@article {1191,
	title = {Comparison of the dynamics of the primary events of bacteriorhodopsin in its trimeric and monomeric states},
	journal = {Biophysical Journal},
	volume = {83},
	number = {3},
	year = {2002},
	note = {Wang, JP Link, S Heyes, CD El-Sayed, MA},
	month = {Sep},
	pages = {1557-1566},
	abstract = {In this paper, femtosecond pump-probe spectroscopy in the visible region of the spectrum has been used to examine the ultrafast dynamics of the retinal excited state in both the native trimeric state and the monomeric state of bacteriorhodopsin (bR). It is found that the excited state lifetime (probed at 490 nm) increases only slightly upon the monomerization of bR. No significant kinetic difference is observed in the recovery process of the bR ground state probed at 570 nm nor in the fluorescent state observed at 850 nm. However, an increase in the relative amplitude of the slow component of bR excited state decay is observed in the monomer, which is due to the increase in the concentration of the 13-cis retinal isomer in the ground state of the light-adapted bR monomer. Our data indicate that when the protein packing around the retinal is changed upon bR monomerization, there is only a subtle change in the retinal potential surface, which is dependent on the charge distribution and the dipoles within the retinal-binding cavity. In addition, our results show that 40\% of the excited state bR molecules return to the ground state on three different time scales: one-half-picosecond component during the relaxation of the excited state and the formation of the J intermediate, a 3-ps component as the J changes to the K intermediate where retinal photoisomerization occurs, and a subnanosecond component during the photocycle.},
	isbn = {0006-3495},
	author = {Wang, Jianping and Link, Stephan and Heyes, C D and El-Sayed, Mostafa A}
}
@article {853,
	title = {The correlation between emission in freshly prepared porous silicon and the carrier density in silicon water},
	journal = {Asian Journal of Spectroscopy},
	volume = {6},
	year = {2002},
	author = {Zou, Bingsuo and Wang, Jianping and El-Sayed, Mostafa A}
}
@article {849,
	title = {Determination of the localization times of electrons and holes in the HgS well in a CdS/HgS/CdS quantum dot{\textendash}quantum well nanoparticle},
	journal = {Physical Review BPhys. Rev. B},
	volume = {66},
	year = {2002},
	month = {2002/11/11/},
	pages = {205312 - },
	publisher = {American Physical Society},
	abstract = {The femtosecond time-resolved electron-hole dynamics of the CdS/HgS/CdS quantum dot{\textendash}quantum well system (QDQW) was investigated as a function of excitation energy. In the transient absorption spectra four bleach bands and a stimulated emission signal in the visible spectral range between 450 and 780 nm were resolved. By using an IR probe pulse at 4.7 μm a transient induced absorption due to intraband transitions was found. The decay and rise times of these signals were measured when the CdS core or the HgS well of the nanoparticles was excited by the pump pulse. After excitation within the HgS well the transient signals rise within the resolution of our pump pulse, while after core excitation slower rise times were measured. From the 1.5 ps rise time of the stimulated emission originating from the HgS well and the intraband hole IR absorption (150 fs) after excitation into the CdS core, the electron localization time (transfer time from the core to the well) is found to be 1.5 ps while that of the hole is \~{}150 fs. This large difference in the observed dynamics of the electron and hole in crossing the CdS/HgS interface is discussed.},
	doi = {10.1103/PhysRevB.66.205312 },
	url = {http://link.aps.org/doi/10.1103/PhysRevB.66.205312},
	author = {Braun, Markus and Link, Stephan and Burda, Clemens and El-Sayed, Mostafa A}
}
@article {1202,
	title = {The effect of surface adsorption on the hyper-Rayleigh scattering of large and small CdSe nanoparticles},
	journal = {Chemical Physics Letters},
	volume = {363},
	number = {5-6},
	year = {2002},
	note = {Landes, C Braun, M El-Sayed, MA},
	month = {Sep},
	pages = {465-470},
	abstract = {Hyper-Rayleigh scattering is used to compare the effect of the addition of n-butylamine to large (3.2 nm) and small (1.6 nm) Use nanoparticles (NPs). It is found that although the adsorption of n-butylamine on large NPs enhances their nonlinear optical response, it has the opposite effect when adsorbed on the small nanoparticles for which the amine adsorption was found previously to induce structural changes. This observation is consistent with an increase in the symmetry of the nanocrystal structure such as would be observed in a phase change from a 4-coordinate wurtzite crystal structure to that of a 6-coordinate zinc-blend form. (C) 2002 Published by Elsevier Science B.V.},
	isbn = {0009-2614},
	doi = {10.1016/s0009-2614(02)01169-7},
	author = {Landes, Christy F. and Braun, Markus and El-Sayed, Mostafa A}
}
@article {851,
	title = {Fourier transform infrared study of the effect of different cations on bacteriorhodopsin protein thermal stability},
	journal = {Biophysical journal},
	volume = {82},
	year = {2002},
	pages = {1598-1606},
	publisher = {Elsevier},
	abstract = {The effect of divalent ion binding to deionized bacteriorhodopsin (dI-bR) on the thermal transitions of the protein secondary structure have been studied by using temperature-dependent Fourier transform infrared (FT-IR) spectroscopy. The native metal ions in bR, Ca2+, and Mg2+, which we studied previously, are compared with Mn2+, Hg2+, and a large, synthesized divalent organic cation, ((Et)3N)2Bu2+. It was found that in all cases of ion regeneration, there is a pre-melting, reversible conformational transition in which the amide frequency shifts from 1665 to 1652cm-1. This always occurs at \~{}80{\textdegree}C, independent of which cation is used for the regeneration. The irreversible thermal transition (melting), monitored by the appearance of the band at 1623cm-1, is found to occur at a lower temperature than that for the native bR but higher than that for acid blue bR in all cases. However, the temperature for this transition is dependent on the identity of the cation. Furthermore, it is shown that the mechanism of melting of the organic cation regenerated bR is different than for the metal cations, suggesting a difference in the type of binding to the protein (either to different sites or different binding to the same site). These results are used to propose specific direct binding mechanisms of the ions to the protein of deionized bR.},
	isbn = {0006-3495},
	doi = {10.1016/S0006-3495(02)75511-2},
	url = {http://dx.doi.org/10.1016/S0006-3495(02)75511-2},
	author = {Heyes, C D and Wang, Jianping and Sanii, L. S. and El-Sayed, Mostafa A}
}
@article {1196,
	title = {Hot electron relaxation dynamics of gold nanoparticles embedded in MgSO4 powder compared to solution: The effect of the surrounding medium},
	journal = {Journal of Physical Chemistry B},
	volume = {106},
	number = {5},
	year = {2002},
	note = {Link, S Furube, A Mohamed, MB Asahi, T Masuhara, H El-Sayed, MA},
	month = {Feb},
	pages = {945-955},
	abstract = {To test the influence of the surrounding medium on the relaxation dynamics of the plasmon band bleach recovery of gold nanoparticles after excitation with femtosecond laser pulses, we embedded 14.5 and 12.1 nm colloidal gold nanoparticles (synthesized electrochemically) in MgSO4 powder and investigated these samples by femtosecond diffuse reflectance spectroscopy. By measuring the relaxation dynamics over a wide range of excitation energies, we found that the fast decay component is slower by about a factor of 2 for the particles in the MgSO4 powder compared to those in solution while no significant change in the slow decay component is observed. In agreement with this observation, we found that adding solvent to the particles embedded in the powder caused a decrease in the relaxation time from about 10 ps to 5 ps for the fast decay component. This leads to the conclusion that the electron-phonon relaxation in these gold nanoparticles depends on the chemical nature and/or physical phase (solid vs solution) of the surrounding medium. A discussion of this in terms of the type of phonon involved, and the nature of the electron-phonon and phonon-phonon relaxation processes is discussed. To our knowledge, this also presents the first time that a transient bleach could be observed by diffuse reflectance spectroscopy.},
	isbn = {1520-6106},
	doi = {10.1021/jp013311k},
	author = {Link, Stephan and Furube, A. and Mohamed, MB and Asahi, T. and Masuhara, H. and El-Sayed, Mostafa A}
}
@article {852,
	title = {The pump power dependence of the femtosecond relaxation of CdSe nanoparticles observed in the spectral range from visible to infrared},
	journal = {The Journal of chemical physics},
	volume = {116},
	year = {2002},
	pages = {3828},
	abstract = {The pump power dependence of the relaxation dynamics of CdSe nanoparticles (NPs) was studied with femtosecond pump probe spectroscopy at observation wavelengths of the first exciton transition at 560 nm, the near infrared (NIR) absorption at 2 μm, and the transient mid-infrared (IR) absorption at 4.5 μm. Excitation with less than one photon per particle leads to bleaching of the excitonic transitions, and the bleach intensity is initially linear to the pump power. At higher pump power the bleach intensity levels off, when complete saturation of the excitonic transition is reached. At the same time, increasing pump power causes an acceleration of the bleach decay, which is due to additional Auger processes when multiple excitons are formed in the NPs. In addition, the pump power effect was investigated for the NIR and IR regions, at 2 and 4.5 μm wavelength, respectively. Whereas the IR transients are very similar to the ones observed for the bleach, the NIR transients behave completely different. No pump power dependence was found for the transients at 2 μm when pumped in a power range from 0.5 to 5 μJ per pulse. The results show that the fs transients in the visible (bleach) and IR (absorption) regions are due to electron relaxation in the conduction band and the NIR transients are due to the relaxation of the hole. Furthermore, it suggests that in the investigated CdSe NPs, Auger processes act much more efficiently on the electrons than for the holes. },
	doi = {10.1063/1.1446851},
	url = {http://link.aip.org/link/doi/10.1063/1.1446851},
	author = {Burda, Clemens and Link, Stephan and Mohamed, MB and El-Sayed, Mostafa A}
}
@article {1195,
	title = {The quenching of CdSe quantum dots photoluminescence by gold nanoparticles in solution},
	journal = {Photochemistry and Photobiology},
	volume = {75},
	number = {6},
	year = {2002},
	note = {Nikoobakht, B Burda, C Braun, M Hun, M El-Sayed, MA},
	month = {Jun},
	pages = {591-597},
	abstract = {The photoluminescence (PL) of CdSe quantum dots (QD) in aqueous media has been studied in the presence of gold nanoparticles (NP) with different shapes. The steady state PL intensity of CdSe QD (1.5-2 nm in size) is quenched in the presence of gold NP. Picosecond bleach recovery and nanosecond time-resolved luminescence measurements show a faster bleach recovery and decrease in the lifetime of the emitting states of CdSe QD in the presence of quenchers. Surfactant-capped gold nanorods (NR) with aspect ratio of 3 and surfactant-capped and citrate-capped nanospheres (NS) of 12 nm diameter were used as quenchers in order to study the effect of shape and surface charge on the quenching rates. The Stern-Volmer kinetics model is used to examine the observed quenching behavior as a function of the quencher concentration. It was found that the quenching rate of NR is more than 1000 times stronger than that of NS with the same capping material. We also found that the quenching rate decreases as the length of the NR decreases, although the overlap between the CdSe emission and the NR absorption increases. This suggests that the quenching is a result of electron transfer rather than long-range (Forster-type) energy transfer processes. The quenching was attributed to the transfer of electron with energies below the Fermi level of gold to the trap holes of CdSe QD. The observed large difference between NR and NS quenching efficiencies was attributed to the presence of the {110} facets only in the NR, which have higher surface energy.},
	isbn = {0031-8655},
	doi = {10.1562/0031-8655(2002)075<0591:tqocqd>2.0.co;2},
	author = {Nikoobakht, Babak and Burda, Clemens and Braun, Markus and Hun, M. and El-Sayed, Mostafa A}
}
@article {1192,
	title = {Refolding of thermally denatured bacteriorhodopsin in purple membrane},
	journal = {Journal of Physical Chemistry B},
	volume = {106},
	number = {3},
	year = {2002},
	note = {Wang, JP Heyes, CD El-Sayed, MA},
	month = {Jan},
	pages = {723-729},
	abstract = {The change in protein conformational structure and retinal chromophore binding state have been examined by using in situ UV-vis, FTIR, and CD spectroscopies during the thermal denaturation and refolding processes in bacteriorhodopsin (bR) of purple membrane (PM), in its native trimeric and in Triton X-100 solubilized monomeric form. For the trimeric bR, it is found that heating bR through its premelting transition (T > 78 degreesC, T-m{\textquoteright}) does not cause any permanent damage in the protein secondary structure, and a reversible refolding occurs when it cools back to room temperature. For the monomeric bR, it is found that it is less thermally stable than the trimer. There is a significant change in its protein secondary structure and a complete dissociation of retinal occurs irreversibly at a temperature as low as 66 degreesC. In addition, it is found that heating the trimeric bR through its main molten state (T > 96 degreesC, T-m) changes the protein secondary structure so that bR does not refold fully into its original secondary structure. Upon cooling back to room temperature, about 90\% of the bound retinal in native bR recovers after being heated through its premelting transition, whereas only about 12\% of bound retinal recovers if bR is heated above its main melting temperature. It is also found that refolded bR molecules with their retinal chromophore rebound have a photocycle and are capable of pumping protons. Our results also suggest that from its molten state, protein secondary structure refolding precedes retinal rebinding to the Schiff base.},
	isbn = {1520-6106},
	doi = {10.1021/jp013131a},
	author = {Wang, Jianping and Heyes, C D and El-Sayed, Mostafa A}
}
@article {1203,
	title = {The role of the native lipids and lattice structure in bacteriorhodopsin protein conformation and stability as studied by temperature-dependent Fourier transform-infrared spectroscopy},
	journal = {Journal of Biological Chemistry},
	volume = {277},
	number = {33},
	year = {2002},
	note = {Heyes, CD El-Sayed, MA},
	month = {Aug},
	pages = {29437-29443},
	abstract = {We report the effect of partial delipidation and monomerization on the protein conformational changes of bacteriorhodopsin (bR) as a function of temperature. Removal of up to 75\% of the lipids is known to have the lattice structure of the purple membrane, albeit as a smaller unit cell, whereas treatment by Triton monomerizes bR into micelles. The effects of these modifications on the protein secondary structure is analyzed by monitoring the protein amide I and amide II bands in the Fourier transform-infrared (FT-IR) spectra. It is found that removal of the first 75\% of the lipids has only a slight effect on the secondary structure at physiological temperature, whereas monomerizing bR into micelles alters the secondary structure considerably. Upon heating, the bR monomer is found to have a very low thermal stability compared with the native bR with its melting point reduced from 97 to 65 degreesC, and the premelting transition in which the protein changes conformation in native bR at 80 degreesC could not be observed. Also, the N-H to N-D exchange of the amide II band is effectively complete at room temperature, suggesting that there are no hydrophobic regions that are protected from the aqueous medium, possibly explaining the low thermal stability of the monomer. On the other hand, 75\% delipidated bR has its melting temperature close to that of the native bR and does have a pre-melting transition, although the pre-melting transition occurs at significantly higher temperature than that of the native bR (91 degreesC compared with 80 degreesC) and is still reversible. Furthermore, we have also observed that the reversibility of this pre-melting transition of both native and partially delipidated bR is time-dependent and becomes irreversible upon holding at 91 degreesC between 10 and 30 min. These results are discussed in terms of the lipid and lattice contribution to the protein thermal stability of native bR.},
	isbn = {0021-9258},
	doi = {10.1074/jbc.M203435200},
	author = {Heyes, C D and El-Sayed, Mostafa A}
}
@article {1198,
	title = {Room temperature optical gain in CdSe nanorod solutions},
	journal = {Journal of Applied Physics},
	volume = {92},
	number = {11},
	year = {2002},
	note = {Link, S El-Sayed, MA},
	month = {Dec},
	pages = {6799-6803},
	abstract = {We have performed femtosecond transient absorption measurements on CdSe nanorods in hexane solution as a function of pump wavelength and pump intensity. We found that although it is not possible to achieve optical gain when pumping at energies (400 nm) high above the band-gap energy, this problem can be circumvented by pumping the CdSe nanorods directly at the lowest 1S transition. We attribute the difference to alternative relaxation pathways and possibly trapping, resulting in a competing induced absorption below the band-gap energy when excitation is carried out at high energies. Our results suggest that it is possible to achieve stimulated emission from CdSe nanoparticles in solution at ambient temperature if the excitation wavelength is chosen properly. (C) 2002 American Institute of Physics.},
	isbn = {0021-8979},
	doi = {10.1063/1.1512689},
	author = {Link, Stephan and El-Sayed, Mostafa A}
}
@article {1200,
	title = {Size effects of PVP-Pd nanoparticles on the catalytic Suzuki reactions in aqueous solution},
	journal = {Langmuir},
	volume = {18},
	number = {12},
	year = {2002},
	note = {Li, Y Boone, E El-Sayed, MA},
	month = {Jun},
	pages = {4921-4925},
	abstract = {A series of poly(N-vinyl-2-pyrrolidone) (PVP)-stabilized Pd nanoparticles with varying particle size are prepared by using the stepwise growth reaction. The effect of Pd particle size on the Suzuki reaction between phenylboronic acid and iodobenzene is investigated by the use of four Pd catalysts with mean particle sizes of 3.0, 3.9, 5.2, and 6.6 nm, respectively. The catalytic activity of the Pd nanoparticles expressed in terms of the initial turnover frequency (moles of the biphenyl product per mole of total surface Pd atoms per min) is found to be in the order of Pd (3.9 nm) > Pd (3.0 nm) approximate to Pd (5.2 nm) > Pd (6.6 nm), indicating that surface Pd atoms do not all have the same reactivity in this reaction. The general trend of increased catalytic activity with the decrease in the particle size suggests that the low-coordination number vertex and edge atoms on the particle surface are active sites for the Suzuki reaction. The lower catalytic activity for the smallest Pd nanoparticles might be due to stronger adsorption of the reaction intermediates on the particle surface, in which the strongly adsorbed species act as a poison to the reaction thereby decreasing the rate of the reaction.},
	isbn = {0743-7463},
	doi = {10.1021/la011469q},
	author = {Li, Y. and Boone, E. and El-Sayed, Mostafa A}
}
@article {1194,
	title = {Surface-enhanced Raman scattering of molecules adsorbed on gold nanorods: off-surface plasmon resonance condition},
	journal = {Chemical Physics Letters},
	volume = {366},
	number = {1-2},
	year = {2002},
	note = {Nikoobakht, B Wang, JP El-Sayed, MA},
	month = {Nov},
	pages = {17-23},
	abstract = {The Raman spectra of several molecules adsorbed on gold nanospheres (NSs) (12 nm in diameter) and nanorods (NRs) (25 nm x 10 nm) are studied using an off-plasmon resonance excitation condition. The studies are carried out in colloidal solution and on solid substrates. Enhancement factors on the order of 10(4)-10(5) are observed for the adsorbed molecules on the NRs, however, no such enhancement was observed on NSs under similar condition. These factors are two orders of magnitude larger than the calculated value using the Wang and Kerker electromagnetic model. This suggests a contribution from the chemical mechanism in the observed enhancement. (C) 2002 Published by Elsevier Science B.V.},
	isbn = {0009-2614},
	doi = {10.1016/s0009-2614(02)01492-6},
	author = {Nikoobakht, Babak and Wang, Jianping and El-Sayed, Mostafa A}
}
@article {1201,
	title = {Thermodynamic and kinetic characterization of the interaction between N-butylamine and similar to 1 nm CdSe nanoparticles},
	journal = {Journal of Physical Chemistry A},
	volume = {106},
	number = {33},
	year = {2002},
	note = {Landes, C El-Sayed, MA},
	month = {Aug},
	pages = {7621-7627},
	abstract = {When butylamine (0.1-0.25 M) is added to a colloidal solution of CdSe nanoparticles (NPs) that are 1-2 nm in diameter, the band gap absorption changes from a broad, relatively weak band centered at 445 nm to a narrow, relatively strong absorption centered at 414 nm. The effect of concentration on the observed spectrum shows an isobestic point, suggesting an equilibrium between two species. Thermodynamic and kinetic studies of this process were carried out. The transition was found to be exothermic, with a size-dependent heat of reaction,that suggests that there is a direct proportionality between the NP size and the exothermicity of the interaction. The decay kinetics of the original peak were studied and compared to the rise kinetics of the 414 nm peak. The decay of the original NPs was biexponential, with a lifetime that depends on the NP size, concentration of reactants,. and the temperature. The rise in the 414 nm peak was found to be multiexponential, reflecting 2 transformations from the ensemble having different NP sizes. A mechanism is proposed for this interaction that depends on the binding of butylamine to the NP surface, followed by a release in energy. The nature of the new species absorbing at 414 nm is discussed.},
	isbn = {1089-5639},
	doi = {10.1021/jp0201130},
	author = {Landes, Christy F. and El-Sayed, Mostafa A}
}
@article {1193,
	title = {Time-resolved long-lived infrared emission from bacteriorhodopsin during its photocycle},
	journal = {Biophysical Journal},
	volume = {83},
	number = {3},
	year = {2002},
	note = {Wang, JP El-Sayed, MA},
	month = {Sep},
	pages = {1589-1594},
	abstract = {The infrared emission observed below 2000 cm(-1) upon exciting retinal in bacteriorhodopsin (bR) is found to have a rise time in the submicrosecond time regime and to relax with two exponential components on the submillisecond to millisecond time scale. These time scales, together with the assignment of this emission to hot vibrations from the all-trans retinal (in bR) and the 13-cis retinal (in the K intermediate), support the recent assignment of the J-intermediate as an electronically excited species (Atkinson et al., J. Phys. Chem. A. 104:4130-4139, 2000) rather than a vibrationally hot K intermediate. A discussion of these time scales of the observed infrared emission is given in terms of the competition between radiative and nonradiative relaxation processes of the vibrational states involved.},
	isbn = {0006-3495},
	author = {Wang, Jianping and El-Sayed, Mostafa A}
}
@article {854,
	title = {Transfer times of electrons and holes across the interface in CdS/HgS/CdS quantum dot quantum well nanoparticles},
	journal = {Chemical physics letters},
	volume = {361},
	year = {2002},
	pages = {446-452},
	publisher = {Elsevier},
	abstract = {The electron and hole trapping times in the HgS well of a 6 nm CdS/HgS/CdS quantum dot quantum well nanoparticle were determined from the rise time of the ultrafast transient absorption in the visible and IR regions as well as the trap fluorescence when the CdS core is excited. From the 1.5 ps observed rise time of the well fluorescence (which is determined by the trapping time of the slowest carrier) and the intraband hole IR absorption (150 fs), the electron localization time is found to be 1.5 ps while that of the hole is \~{}150 fs. This large difference in the observed dynamics of the electron and hole in crossing the CdS/HgS interface is discussed.},
	isbn = {0009-2614},
	doi = {10.1016/S0009-2614(02)01001-1 },
	url = {http://dx.doi.org/10.1016/S0009-2614(02)01001-1 },
	author = {Braun, Markus and Link, Stephan and Burda, Clemens and El-Sayed, Mostafa A}
}
@article {1197,
	title = {Transition from nanoparticle to molecular behavior: a femtosecond transient absorption study of a size-selected 28 atom gold cluster},
	journal = {Chemical Physics Letters},
	volume = {356},
	number = {3-4},
	year = {2002},
	note = {Link, S El-Sayed, MA Schaaff, TG Whetten, RL},
	month = {Apr},
	pages = {240-246},
	abstract = {The ultrafast electron dynamics of chemically prepared gold nanoclusters with a 28 atom gold core surrounded by 16 glutathione molecules were investigated. After excitation with femtosecond laser pulses these clusters show an induced transient absorption in the visible from 2.58 to 1.65 eV (480-750 nm) with a maximum around 2.07 eV (600 nm). The excited state relaxation shows a biexponential decay with a subpicosecond and a longer nanosecond decay time independent of the laser pump power. These results are different from those observed previously for larger gold nanoparticles, which suggests that the Au-28-glutathione system shows molecular properties. (C) 2002 Elsevier Science B.V. All rights reserved.},
	isbn = {0009-2614},
	doi = {10.1016/s0009-2614(02)00306-8},
	author = {Link, Stephan and El-Sayed, Mostafa A and Schaaff, T. G. and Whetten, R. L.}
}
@article {1199,
	title = {Visible to infrared luminescence from a 28-atom gold cluster},
	journal = {Journal of Physical Chemistry B},
	volume = {106},
	number = {13},
	year = {2002},
	note = {Link, S Beeby, A FitzGerald, S El-Sayed, MA Schaaff, TG Whetten, RL},
	month = {Apr},
	pages = {3410-3415},
	abstract = {The luminescence properties of chemically prepared gold nanoclusters, each composed of a 28-atom core and a glutathione (GSH) adsorbate layer consisting of 16 molecules, were investigated. These clusters show a distinct absorption onset at 1.3 eV corresponding to the opening of an electronic gap within the conduction band (HOMO-LUMO gap). Here we report on the radiative properties of these molecular-like Bald clusters. By using a combination of different detectors with sensitivities in the visible to the infrared (2.0-0.8 eV), a broad luminescence extending over this entire spectral range was observed. Our results further suggest that the luminescence can be separated into two bands with maxima around 1.5 and 1.15 eV indicating that radiative recombination between the ground state and two distinctively different excited states takes place. The: origin of the observed luminescence bands is discussed using a solid state as well as a molecular model for the electronic structure and relaxation of the clusters. The total quantum yield of the luminescence: as measured at ambient temperature was approximated to be about (3.5 +/- 1.0) x 10(-3).},
	isbn = {1520-6106},
	doi = {10.1021/jp014259v},
	author = {Link, Stephan and Beeby, A. and FitzGerald, S. and El-Sayed, Mostafa A and Schaaff, T. G. and Whetten, R. L.}
}
@article {1204,
	title = {Direct observation of charge-transfer dynamics in a conjugated conducting polymer poly (3-octylthiophene)-fullerene composite by time-resolved infrared spectroscopy},
	journal = {Physical Review B},
	volume = {64},
	number = {23},
	year = {2001},
	note = {Wang, JP Li, Y Hong, XY El-Sayed, MA},
	month = {Dec},
	abstract = {Transient infrared-active vibrational (IRAV) modes observed in the pi -conjugated conducting polymers upon photoexcitation are usually used to characterize the dynamics of the photoinduced charge separation and recombination processes. In this paper, the dynamic behavior of photogenerated charge carrier in the poly(3-octylthiophene) (P3OT) conducting polymer doped with fullerene (C(60)) has been studied by using step-scan time-resolved Fourier-transform infrared spectroscopy at room temperature in the 2500-900-cm(-1) (0.31-0.11-eV) frequency region. Upon photoexcitation with a 10-ns laser pulses, it is observed that IRAV modes appear in the similar vibrational frequency regions for pure P3OT and C(60)-doped P3OT; however, the observed IRAV modes is enhanced by 800\% in intensity in the presence of small amount of C(60) (e.g., 10\%). Our results also show that the charge separation occurs instantaneously within the laser pulse width (10 ns), whereas the charge recombination processes occur in the microseconds to a few milliseconds time domain. In addition, the observed enhancement in the IRAV modes upon C(60) doping indicates an enhanced photogeneration efficiency of the charge separation.},
	isbn = {1098-0121},
	doi = {10.1103/PhysRevB.64.235413},
	author = {Wang, Jianping and Li, Y. and Hong, X. Y. and El-Sayed, Mostafa A}
}
@article {1206,
	title = {The effect of metal cation binding on the protein, lipid and retinal isomeric ratio in regenerated bacteriorhodopsin of purple membrane},
	journal = {Photochemistry and Photobiology},
	volume = {73},
	number = {5},
	year = {2001},
	note = {Wang, JP El-Sayed, MA},
	month = {May},
	pages = {564-571},
	abstract = {The effect of metal cation binding on bacteriorhodopsin (bR) in purple membrane has been examined using in situ attenuated total reflection-Fourier transform infrared difference spectroscopy in aqueous media. It is known that adding metal cations to deionized bR regenerates the purple state from its blue state and recovers the proton pump function, During this process, infrared spectral changes in the frequency region of 1800-1000 cm(-1) are monitored. The results reveal that metal cation binding affects the protein conformation, the retinal isomeric composition as well as lipid head groups. It is also observed that metal cation binding induces conformational changes in the alpha (1)-helix region of bR, converting the portion of its alpha (1)-helical domain into beta -turn or disordered coil, In addition, the influence of Ho3+ binding on the protein and lipid is observed to be larger than that of Ca2+, These results suggest that some of the metal cation binding sites are on the membrane lipid domain, while others could be on the intrahelical domain or interhelical loops where the Asp and Glu are located (binding with their COO- groups). Our results also suggest that the removal of the C-terminal of bR increase the accessibility of the binding site of metal cations, which affects protein conformational structure. All these observations are discussed in terms of the two proposals given in the literature regarding the metal cation binding sites.},
	isbn = {0031-8655},
	doi = {10.1562/0031-8655(2001)073<0564:teomcb>2.0.co;2},
	author = {Wang, Jianping and El-Sayed, Mostafa A}
}
@article {1214,
	title = {The effect of stabilizers on the catalytic activity and stability of Pd colloidal nanoparticles in the Suzuki reactions in aqueous solution},
	journal = {Journal of Physical Chemistry B},
	volume = {105},
	number = {37},
	year = {2001},
	note = {Li, Y El-Sayed, MA},
	month = {Sep},
	pages = {8938-8943},
	abstract = {Transition metal nanoparticles used in catalysis in solution are stabilized by capping the surfaces that are supposed to be used for catalysis. Determining, how these two properties, that is, the catalytic activity and stability of nanoparticles, change as different capping materials are used is the aim of this work. Pd nanoparticles prepared by the reduction of metal salts in the presence of three different stabilizers-hydroxyl-terminated poly(amido-amine) (PAMAM) dendrimers (Gn-OH, where Gn represents the nth generation), block copolymer polystyrene-b-poly(sodium acrylate) and poly (N-vinyl-2-pyrrolidone) (PVP)-are used as catalysts in the Suzuki reactions in an aqueous medium to investigate the effects of these stabilizers on the metallic nanoparticle catalytic activity and stability. The stability of the Pd nanoparticles is measured by the tendency of the nanoparticles to give Pd black powder after the catalytic reaction. The Suzuki reaction is a good "acid test" for examining the stability of these nanoparticles, as it takes place when refluxed at about 100 degreesC for 24 h. The stability is found to depend on the type of the stabilizer, the reactant, and the base used in the reaction system. Pd nanoparticles stabilized by block copolymer, G3 dendrimer, and PVP are found to be efficient catalysts for the Suzuki reactions between phenylboronic acid (or 2-thiopheneboronic acid) and iodobenzene. G4 dendrimer is found to be an effective stabilizer; however, strong encapsulation of Pd particles in the dendrimer results in a loss of catalytic activity. The Suzuki reactions between arylboronic acids and bromoarenes catalyzed by Pd nanoparticles result in byproducts due to the homo-coupling of bromoarenes. A summary of the catalytic activity and stability of the Pd nanoparticles in these different systems is tabulated. As one would expect. these two properties are anticorrelated that is the most stable is the least catalytic active.},
	isbn = {1089-5647},
	doi = {10.1021/jp010904m},
	author = {Li, Y. and El-Sayed, Mostafa A}
}
@article {1217,
	title = {Effect of temperature, pH, and metal ion binding on the secondary structure of bacteriorhodopsin: FT-IR study of the melting and premelting transition temperatures},
	journal = {Biochemistry},
	volume = {40},
	number = {39},
	year = {2001},
	note = {Heyes, CD El-Sayed, MA},
	month = {Oct},
	pages = {11819-11827},
	abstract = {We have measured the temperature dependence of the FT-IR spectra of bacteriorhodopsin (bR) as a function of the pH and of the divalent cation regeneration with Ca2+ and Mg2+. It has been found that although the irreversible melting transition shows a strong dependence on the pH of the native bR, the premelting reversible transition at 78-80 degreesC shows very little variation over the pH range studied. It is further shown that the acid blue bR shows a red-shifted amide I spectrum at physiological temperature, which shows a more typical alpha -helical frequency component at 1652 cm(-1) and could be the reason for the observed reduction of its melting temperature and lack of an observed premelting transition. Furthermore, the thermal transitions for Ca2+- and Mg2+-regenerated bR (Ca-bR and Mg-bR, respectively) each show a premelting transition at the same 78-80 degreesC temperature as the native purple membrane, but the irreversible melting transition has a slight dependence on the cation identity. The pH dependence of the Ca2+-regenerated bR is studied, and neither transition varies over the pH range studied. These results are discussed in terms of the cation contribution to the secondary structural stability in bR.},
	isbn = {0006-2960},
	doi = {10.1021/bi002594o},
	author = {Heyes, C D and El-Sayed, Mostafa A}
}
@article {1209,
	title = {Evidence for bilayer assembly of cationic surfactants on the surface of gold nanorods},
	journal = {Langmuir},
	volume = {17},
	number = {20},
	year = {2001},
	note = {Nikoobakht, B El-Sayed, MA},
	month = {Oct},
	pages = {6368-6374},
	abstract = {The surface structure of gold nanorods (NRs) capped with cationic surfactants in water was studied by FTIR, thermogravimetric analysis (TGA), and transmission electron microscopy (TEM). For gold nanorods, the FTIR results show the formation of new bands, which indicate binding of the surfactant headgroup to the surface of the NR. These bands are stable at temperatures as high as 350 degreesC. For a surfactant mixture (used as capping material), TGA shows a weak weight loss peak at 235 degreesC and a strong peak at 298 degreesC assigned to the surfactant molecules in monomer and aggregated forms, respectively. For gold nanorods, three weight loss peaks at about 230, 273, and 344 degreesC are observed. For gold nanospheres (NSs), TGA shows a strong mass loss at 225 degreesC and two weak mass loss peaks at 255 and 288 degreesC. The released material after combustion in the TGA process was analyzed by FTIR spectroscopy and found to be CO2. Our results suggest the following for both NRs and NSs: (1) There are two different binding modes for the surfactant molecules capping these nanoparticles. (2) Surfactant molecules form a bilayer structure around the gold nanoparticles in which the inner layer is bound to the gold surface via the surfactant headgroups. (3) With increase of the temperature, the outer layer desorbs at lower temperature and consequently the inner layer leaves the surface at higher temperature. (4) The higher desorption temperature of the bilayer in the NRs compared to NSs is explained in terms of the difference in packing of the surfactant molecules and their adsorption energy to the different facets present in these nanoparticles. (5) TEM results suggest that the shape transformation of NRs to NSs occurs as the inner layer is released from the surface. (6) The CH2 rocking mode at 720 cm(-1) suggests that the methylene chains have free rotation and surfactants are packed in a hexagonal structure.},
	isbn = {0743-7463},
	doi = {10.1021/la010530o},
	author = {Nikoobakht, Babak and El-Sayed, Mostafa A}
}
@article {1212,
	title = {Formation of quantum-dot quantum-well heteronanostructures with large lattice mismatch: ZnS/CdS/ZnS},
	journal = {Journal of Chemical Physics},
	volume = {114},
	number = {4},
	year = {2001},
	note = {Little, RB El-Sayed, MA Bryant, GW Burke, S},
	month = {Jan},
	pages = {1813-1822},
	abstract = {Two-dimensional heterostructures have been exploited extensively in the synthesis of optoelectronic devices. Structures with small lattice mismatch can be synthesized readily. Large lattice mismatch in II-VI film heterostructures makes synthesis of devices with these materials more difficult. However, these large mismatch heterostructures usually have useful optical properties. One such heterostructure is the ZnS/CdS system with a large exciton binding energy and a large band gap useful for blue-green emitting devices. In this work, small II-VI nanoparticles are studied. We show that II-VI heterostructures can be made in quantum dots, despite the large bulk lattice mismatch. Two well-known techniques are combined to synthesize first very small ZnS and CdS seed nanoparticles and then do nanoepitaxy on them to produce ZnS/CdS core/shell quantum-dot quantum-well heteronanostructures. These structures are characterized by UV visible absorbance. Measured spectra are compared with electronic level structures calculated for the fabricated heteronanostructures with a tight-binding model. The consistency of the observed spectra with the predicted transitions indicates that the desired core/shell and core/shell/clad structures were grown. The metastability of the ZnS/CdS/ZnS heteronanostructures is attributed to low-temperature construction and small crystal size (<3 nm). The small particle size should produce large surface forces and ZnS core contraction. Also, the small particle size should accommodate strain, as a result of the ZnS/CdS interfacial curvature, which is not possible for planar systems. Furthermore, this new structure is kinetically stabilized against alloying by the large size difference between the Cd2+ ion and Zn2+ ions. We suggest that all of these factors contribute to the formation of quantum-dot quantum-well ZnS/CdS/ZnS heteronanostructures. (C) 2001 American Institute of Physics.},
	isbn = {0021-9606},
	doi = {10.1063/1.1333758},
	author = {Little, Reginald and El-Sayed, Mostafa A and Bryant, G. W. and Burke, S.}
}
@article {1210,
	title = {Hot electron and phonon dynamics of gold nanoparticles embedded in a gel matrix},
	journal = {Chemical Physics Letters},
	volume = {343},
	number = {1-2},
	year = {2001},
	note = {Mohamed, MB Ahmadi, TS Link, S Braun, M El-Sayed, MA},
	month = {Jul},
	pages = {55-63},
	abstract = {Using pump-probe technique, the dynamics of the hot carriers in metallic nanodots induced by femtosecond laser pulses are investigated in gold nanoparticles embedded in hydrogel and in organic gel and compared to that in aqueous solution. We found that changing the surrounding matrix from aqueous solution to hydrogel and then to organic gel leads to a large increase in the relaxation time of both the electron-phonon (e-ph) and the phonon-phonon (ph-ph) coupling. Furthermore, the ph-ph relaxation time becomes sensitive to the type of the organic solvent trapped in the gel network. This indicates that the relaxation dynamics depend on the thermal conductivity, chemical structure and the molecular dynamics of the surrounding medium. (C) 2001 Elsevier Science BN. All rights reserved.},
	isbn = {0009-2614},
	doi = {10.1016/s0009-2614(01)00653-4},
	author = {Mohamed, MB and Ahmadi, Temer S. and Link, Stephan and Braun, Markus and El-Sayed, Mostafa A}
}
@article {855,
	title = {On the Nanoparticle to Molecular Size Transition:  Fluorescence Quenching Studies},
	journal = {The Journal of Physical Chemistry B},
	volume = {105},
	year = {2001},
	note = {doi: 10.1021/jp0118726},
	month = {2001},
	pages = {10554 - 10558},
	publisher = {American Chemical Society},
	abstract = {Semiconductor nanoparticles, NPs, exhibit fluorescence properties that are closely related to the nature of their surface. CdSe NPs that range in size from 2 to 15 nm in diameter fluoresce with both near-band-edge emission and deep-trap emission, depending on the quality of the surface. When butylamine is added to colloidal solutions of NPs in this size range, the amine is thought to bind to the NP surface and eliminate radiant recombination pathways that lead to luminescence. Since the amine binds to the NP surface, the decrease in fluorescence intensity does not follow standard molecular models of collisional fluorescence quenching. NPs that are smaller than ?2 nm are composed entirely of a discontinuous arrangement of atoms that are all in constant chemical contact with capping material, solvent, and contaminants. When butylamine is added to solutions of these smaller NPs, the fluorescence quenching follows more standard collisional quenching models. Thus, by monitoring the interaction between NPs and a hole acceptor such as butylamine, one can observe the transition from NP, with atoms both in the core and on the surface, to molecular cluster, with no core atoms to dominate the electron density, but with only surface atoms that can participate in molecular processes such as electron transfer.Semiconductor nanoparticles, NPs, exhibit fluorescence properties that are closely related to the nature of their surface. CdSe NPs that range in size from 2 to 15 nm in diameter fluoresce with both near-band-edge emission and deep-trap emission, depending on the quality of the surface. When butylamine is added to colloidal solutions of NPs in this size range, the amine is thought to bind to the NP surface and eliminate radiant recombination pathways that lead to luminescence. Since the amine binds to the NP surface, the decrease in fluorescence intensity does not follow standard molecular models of collisional fluorescence quenching. NPs that are smaller than ?2 nm are composed entirely of a discontinuous arrangement of atoms that are all in constant chemical contact with capping material, solvent, and contaminants. When butylamine is added to solutions of these smaller NPs, the fluorescence quenching follows more standard collisional quenching models. Thus, by monitoring the interaction between NPs and a hole acceptor such as butylamine, one can observe the transition from NP, with atoms both in the core and on the surface, to molecular cluster, with no core atoms to dominate the electron density, but with only surface atoms that can participate in molecular processes such as electron transfer.},
	isbn = {1520-6106},
	url = {http://dx.doi.org/10.1021/jp0118726},
	author = {Landes, Christy F. and Braun, Markus and El-Sayed, Mostafa A}
}
@article {1216,
	title = {Observation of large changes in the band gap absorption energy of small CdSe nanoparticles induced by the adsorption of a strong hole acceptor},
	journal = {Nano Letters},
	volume = {1},
	number = {11},
	year = {2001},
	note = {Landes, C Braun, M Burda, C El-Sayed, MA},
	month = {Nov},
	pages = {667-670},
	abstract = {When butylamine In relatively high concentrations (0.1-0.25 M) is added to a colloidal solution of CdSe nanoparticles (NPs) that are approximately 1.6 nm in diameter, the band gap absorption changes from a broad, relatively weak absorption centered at 445 nm to a narrow, relatively strong absorption centered at 414 nm. The effect of concentration on the observed spectrum shows an isobestic point, suggesting an equilibrium between two species. The possible mechanisms for such a transformation are discussed.},
	isbn = {1530-6984},
	doi = {10.1021/nl015619t},
	author = {Landes, Christy F. and Braun, Markus and Burda, Clemens and El-Sayed, Mostafa A}
}
@article {1215,
	title = {Photoluminescence of CdSe nanoparticles in the presence of a hole acceptor: n-butylamine},
	journal = {Journal of Physical Chemistry B},
	volume = {105},
	number = {15},
	year = {2001},
	note = {Landes, C Burda, C Braun, M El-Sayed, MA},
	month = {Apr},
	pages = {2981-2986},
	abstract = {Addition of butylamine to a solution of colloidal CdSe nanoparticles (NPs) caused a decrease in fluorescence intensity, with no effect on the picosecond bleach recovery of the exciton formation or on the luminescence dynamics. The relative fluorescence quantum yield was found to decrease with increasing butylamine concentration and to level off at high concentrations, but the fluorescence lifetimes were not influenced. The nonlinear concentration dependence of the fluorescence quantum yield did not follow the Stern-Volmer equation. This is in agreement with the observation that the CdSe luminescence lifetime was not affected by the addition of butylamine. A mechanism is proposed in which the emission observed in CdSe is assumed to result from the combination of surface-trapped electrons and holes. n-Butylamine occupies hole sites, thus blocking the recombination process, which results in decreasing the density of luminescent centers. These results will be discussed in terms of the nature of the binding sites of the amine on the nanoparticle surface.},
	isbn = {1089-5647},
	doi = {10.1021/jp0041050},
	author = {Landes, Christy F. and Burda, Clemens and Braun, Markus and El-Sayed, Mostafa A}
}
@article {1211,
	title = {The relaxation dynamics of the excited electronic states of retinal in bacteriorhodopsin by two-pump-probe femtosecond studies},
	journal = {Proceedings of the National Academy of Sciences of the United States of America},
	volume = {98},
	number = {15},
	year = {2001},
	note = {Logunov, SL Volkov, VV Braun, M El-Sayed, MA},
	month = {Jul},
	pages = {8475-8479},
	abstract = {We present the results of two-pump and probe femtosecond experiments designed to follow the relaxation dynamics of the lowest excited state (S-1) populated by different modes. In the first mode, a direct (S-0 --> S-1) radiative excitation of the ground state is used. In the second mode, an indirect excitation is used where the S-1 state is populated by the use of two femtosecond laser pulses with different colors and delay times between them. The first pulse excites the S-0 --> S-1 transition whereas the second pulse excites the S-1 --> S-n transition. The nonradiative relaxation from the S-n state populates the lowest excited state. Our results suggest that the S1 state relaxes faster when populated nonradiatively from the S-n state than when pumped directly by the S-0 --> S-1 excitation. Additionally, the S-n --> S-1 nonradiative relaxation time is found to change by varying the delay time between the two pump pulses. The observed dependence of the lowest excited state population as well as its dependence on the delay between the two pump pulses are found to fit a kinetic model in which the S-n state populates a different surface (called Si) than the one being directly excited (S-1). The possible involvement of the A(g) type states, the J intermediate, and the conical intersection leading to the S-0 or to the isomerization product (K intermediate) are discussed in the framework of the proposed model.},
	isbn = {0027-8424},
	doi = {10.1073/pnas.141220198},
	author = {Logunov, Stephan L. and Volkov, V. V. and Braun, Markus and El-Sayed, Mostafa A}
}
@article {1208,
	title = {Self-assembly of platinum nanoparticles of various size and shape},
	journal = {Journal of Physical Chemistry A},
	volume = {105},
	number = {23},
	year = {2001},
	note = {Petroski, JM Green, TC El-Sayed, MA},
	month = {Jun},
	pages = {5542-5547},
	abstract = {The addition of dodecanethiol to a polydisperse platinum colloidal aqueous solution capped with acrylic acid leads to self-assembled monolayers which not only contain various sizes, but also various shapes of nanoparticles. Assembled monolayers arranged in hcp arrays are achieved for mixed shape-samples. In;the case of the assembly of cubic nanoparticles, cubic closest packing is achieved when the size difference between the nanoparticles is less than 25\% (or between 6 and 8 nm). The ccp array is disrupted when the size difference is between 25 and 60\% or there is a mixture of shapes. Finally, size segregation is seen in regions where the size difference is more than 60\% with the resultant assembly being hcp no matter what the shape.},
	isbn = {1089-5639},
	doi = {10.1021/jp0019207},
	author = {Petroski, J. M. and Green, T.C. and El-Sayed, Mostafa A}
}
@article {1218,
	title = {Some interesting properties of metals confined in time and nanometer space of different shapes},
	journal = {Accounts of Chemical Research},
	volume = {34},
	number = {4},
	year = {2001},
	note = {El-Sayed, MA},
	month = {Apr},
	pages = {257-264},
	abstract = {The properties of a material depend on the type of motion its electrons can execute, which depends on the space available for them (i.e., on the degree of their spatial confinement). Thus, the properties of each material are characterized by a specific length scale, usually on the nanometer dimension. If the physical size of the material is reduced below this length scale, its properties change and become sensitive to its size and shape. In this Account we describe some of the observed new chemical, optical, and thermal properties of metallic nanocrystals when their size is confined to the nanometer length scale and their dynamical processes are observed on the femto- to picosecond time scale.},
	isbn = {0001-4842},
	doi = {10.1021/ar960016n},
	author = {El-Sayed, Mostafa A}
}
@article {1213,
	title = {Spectroscopic determination of the melting energy of a gold nanorod},
	journal = {Journal of Chemical Physics},
	volume = {114},
	number = {5},
	year = {2001},
	note = {Link, S El-Sayed, MA},
	month = {Feb},
	pages = {2362-2368},
	abstract = {Gold nanorods in colloidal solution can be melted into spherical nanoparticles by excitation with intense femtosecond laser pulses of the proper energy. The threshold of the laser pulse energy for the complete melting of the nanorods with a mean aspect ratio of 4.1 in solution is determined by observing the change in the absorption intensity of the longitudinal absorption band (measure of the rod concentration) at 800 nm with increasing number of laser pulses of known energy. The number of laser pulses needed to reduce the band intensity (rod concentration) by 1/e of its initial value is determined as the laser energy per pulse increases. For pulses of lower energy than threshold, it is found that the number of pulses required to melt the gold nanorods present in solution increases significantly with decreasing laser pulse energy. Above threshold, this number is constant since the additional absorbed laser energy will only further heat the particles to temperatures above their melting point. The gold concentration in the colloidal solution is measured using inductively coupled plasma atomic emission spectroscopy (ICP-AES), from which the gold nanorod concentration is determined from the known shape and size distribution obtained from transmission electron microscopy (TEM) results. A simple analysis using the determined threshold energy and the nanorod concentration showed that it takes an average of similar to 60 femtojoule (fJ) to melt a single gold nanorod. Experiments using 820 nm as well as 410 nm femtosecond laser pulses yield similar values, indicating that the laser induced shape transformation of the nanorods is independent of the irradiation wavelength and that this process is therefore photothermal in origin. (C) 2001 American Institute of Physics.},
	isbn = {0021-9606},
	doi = {10.1063/1.1336140},
	author = {Link, Stephan and El-Sayed, Mostafa A}
}
@article {1205,
	title = {Temperature-jump investigations of the kinetics of hydrogel nanoparticle volume phase transitions},
	journal = {Journal of the American Chemical Society},
	volume = {123},
	number = {45},
	year = {2001},
	note = {Wang, JP Gan, DJ Lyon, LA El-Sayed, MA},
	month = {Nov},
	pages = {11284-11289},
	abstract = {The dynamics of the deswelling and swelling processes in thermoresponsive poly-N-isopropylacrylamide (pNIPAm) hydrogel nanoparticles have been studied by using time-resolved transmittance measurements, in combination with a nanosecond laser-induced temperature-jump (T-jump) technique. A decrease in the solution transmittance associated with deswelling of the particles has been observed as the solution temperature traverses the volume phase transition temperature of the particles. Upon inducing the T-jump, the deswelling transition only occurs in a small percentage (< 10\%) of the particle volume, which was found to be a thin periphery layer of the particles. The particle deswelling occurs on the microsecond time scale, and as shown previously, the collapse time can be tuned via adding small amounts of hydrophobic component to the particle shell. In contrast, the reswelling of the particles was thermodynamically controlled by bath equilibration, and only small differences in particle reswelling kinetics were found due to sluggish heat dissipation (millisecond time scale) from the sample cell.},
	isbn = {0002-7863},
	doi = {10.1021/ja016610w},
	author = {Wang, Jianping and Gan, D. J. and Lyon, L. A. and El-Sayed, Mostafa A}
}
@article {1207,
	title = {Time-resolved Fourier transform infrared spectroscopy of the polarizable proton continua and the proton pump mechanism of bacteriorhodopsin},
	journal = {Biophysical Journal},
	volume = {80},
	number = {2},
	year = {2001},
	note = {Wang, JP El-Sayed, MA},
	month = {Feb},
	pages = {961-971},
	abstract = {Nanosecond-to-microsecond time-resolved Fourier transform infrared (FTIR) spectroscopy in the 3000-1000-cm(-1) region has been used to examine the polarizable proton continua observed in bacteriorhodopsin (bR) during its photocycle. The difference in the transient FTIR spectra in the time domain between 20 ns and 1 ms shows a broad absorption continuum band in the 2100-1800-cm(-1) region, a bleach continuum band in the 2500-2150-cm(-1) region, and a bleach continuum band above 2700 cm(-1). According to Zundel (G. Zundel, 1994, J. Mol. Struct. 322.33-42), these continua appear in systems capable of forming polarizable hydrogen bonds. The formation of a bleach continuum suggests the presence of a polarizable proton in the ground state that changes during the photocycle. The appearance of a transient absorption continuum suggests a change in the polarizable proton or the appearance of new ones. It is found that each continuum has a rise time of less than 80 ns and a decay time component of similar to 300 mus. In addition, it is found that the absorption continuum in the 2100-1800-cm(-1) region has a slow rise component of 190 ns and a fast decay component of similar to 60 mus. Using these results and those of the recent x-ray structural studies of bR(570) and M-412 (H. Luecke, B. Schobert, H.T. Richter, J.-P. Cartailler, and J. K. Lanyi, 1999, Science 286:255-260), together with the already known spectroscopic properties of the different intermediates in the photocycle, the possible origins of the polarizable protons giving rise to these continua during the bR photocycle are proposed. Models of the proton pump are discussed in terms of the changes in these polarizable protons and the hydrogen-bonded chains and in terms of previously known results such as the simultaneous deprotonation of the protonated Schiff base (PSB) and Tyr185 and the disappearance of water molecules in the proton release channel during the proton pump process.},
	isbn = {0006-3495},
	author = {Wang, Jianping and El-Sayed, Mostafa A}
}
@article {1219,
	title = {Variation of the thickness and number of wells in the CdS/HgS/CdS quantum dot quantum well system},
	journal = {Journal of Physical Chemistry A},
	volume = {105},
	number = {23},
	year = {2001},
	note = {Braun, M Burda, C El-Sayed, MA},
	month = {Jun},
	pages = {5548-5551},
	abstract = {We report on the first chemically prepared multilayer quantum well structure in a semiconductor quantum dot. By subsequent precipitation of HgS, CdS, HgS, and again CdS from aqueous solution, we obtained nanoparticles which contain two HBS quantum wells separated by a double layer of CdS. The:core:and the capping material is also CdS. The two-well system was characterized by absorption and emission spectroscopy, which clearly reveal the formation of a two-well and not a single double-layered quantum well system. This system allows to study the interaction of quantum wells that are separated by different thicknesses of the CdS barriers. The radiative and relaxation dynamics of the new two-well system are compared with the dynamics of systems having a single-layer well and a double-layer well system.},
	isbn = {1089-5639},
	doi = {10.1021/jp010002l},
	author = {Braun, Markus and Burda, Clemens and El-Sayed, Mostafa A}
}
@article {1230,
	title = {Activation energy of the reaction between hexacyanoferrate(III) and thiosulfate ions catalyzed by platinum nanoparticles},
	journal = {Journal of Physical Chemistry B},
	volume = {104},
	number = {47},
	year = {2000},
	note = {Li, Y Petroski, J El-Sayed, MA},
	month = {Nov},
	pages = {10956-10959},
	abstract = {A temperature-dependent study was carried out for the platinum-nanoparticle-catalyzed electron-transfer reaction between hexacyanoferrate(III) and thiosulfate ions in the temperature range of 20-70 degreesC. The Pt nanoparticles are dominantly truncated octahedral in shape and have an average particle size of 7.0 +/- 0.8 nm. The catalyzed reaction is compared with the uncatalyzed reaction in the same temperature range. The activation energy of the reaction is found to be 38.3 +/- 2.0 kJ/mol for the uncatalyzed reaction and 17.6 +/- 0.9 kJ/mol for the catalyzed reaction in the lower temperature range (20-50 degreesC). In the higher temperature range (50-70 degreesC), the rate remains nearly constant. This behavior is attributed to the cancellation of two effects: the temperature dependence of the catalytic reaction and the decrease in the catalyst surface area due to the increase of nanoparticle aggregation.},
	isbn = {1089-5647},
	doi = {10.1021/jp002569s},
	author = {Li, Y. and Petroski, J. M. and El-Sayed, Mostafa A}
}
@article {1222,
	title = {The effect of the protein conformation change on bacteriorhodopsin photocycle},
	journal = {Biophysical Journal},
	volume = {78},
	number = {1},
	year = {2000},
	note = {Wang, JP El-Sayed, MAPart 2},
	month = {Jan},
	pages = {159A-159A},
	isbn = {0006-3495},
	author = {Wang, Jianping and El-Sayed, Mostafa A}
}
@article {1233,
	title = {Femtosecond dynamics of a simple merocyanine dye: Does deprotonation compete with isomerization?},
	journal = {Journal of the American Chemical Society},
	volume = {122},
	number = {28},
	year = {2000},
	note = {Burda, C Abdel-Kader, MH Link, S El-Sayed, MA},
	month = {Jul},
	pages = {6720-6726},
	abstract = {The primary photochemistry of the trans isomer of a simple merocyanine dye of the stilbazolium betaine type 1-methyl-4-(4{\textquoteright}-hydroxytyryl)pyridinium betaine (M-trans) and its conjugate acid MHtrans+ in aqueous solution is studied by femtosecond time-resolved pump probe spectroscopy. The measured rate of the primary photodynamics is determined to be k = 1.1 x 10(12) s(-1) for M-trans at pH 10 and 0.8 x 10(12) s(-1) for MHtrans+ at pH 6. This was assigned to either conformational changes or a simple vibrational relaxation before the actual isomerization takes place. Wavelength excitation studies give support for the former assignment. These results an discussed in terms of the recent results found for the primary processes of retinal in bacteriorhodopsin. Time-resolved transient measurements show that no excited-state deprotonation of MHtrans+ occurs in aqueous solutions at pH 6 or pH 0, suggesting that the deprotonation occurs on a longer time scale than the picosecond time domain. This is in agreement with present theories of intermolecular proton-transfer reactions, which require solvent reorganization as well as the time of deprotonation estimated from the pK(a) value of this molecule in the excited state. The results of our MO calculations on the electronic structure of these two compounds could account for the fact that, while MHtrans+ photoisomerizes, its deprotonated form does not.},
	isbn = {0002-7863},
	doi = {10.1021/ja993940w},
	author = {Burda, Clemens and Abdel-Kader, M. H. and Link, Stephan and El-Sayed, Mostafa A}
}
@article {1229,
	title = {Femtosecond transient-absorption dynamics of colloidal gold nanorods: Shape independence of the electron-phonon relaxation time},
	journal = {Physical Review B},
	volume = {61},
	number = {9},
	year = {2000},
	note = {Link, S Burda, C Mohamed, MB Nikoobakht, B El-Sayed, MA},
	month = {Mar},
	pages = {6086-6090},
	abstract = {We studied the femtosecond dynamics of colloidal gold nanorods encapsulated in micelles after excitation with 400 nm pulses of 100 fs duration. It is found that the laser heating of the electron gas of gold nanorods with an average aspect ratio of 3.8 leads to the bleaching of both the transverse and longitudinal mode of the surface plasmon oscillation at 520 and 750 nm. The bleach recovers with the same time constant for both the transverse and longitudinal oscillation, for gold nanodots prepared by photothermal reshaping of the rods as well as for nanodots synthesized chemically by citrate reduction (and known to have twin boundaries and surface defects). Since the bleach recovery on the 3 ps time scale is assigned to electron-phonon relaxation processes, these results suggest that phonon dependent relaxation processes in gold nanoparticles are independent of the shape, size, type of the surfaces, or the mode of the surface plasmon, oscillation excited. The fact that the mean free path of the electron in metallic gold is in the nanometer length scale (similar to 50 nm) raised the question of the importance of surface scattering to the electron-phonon relaxation process in gold nanoparticles. Our previous studies showed little dependence of the relaxation rate of the size of gold nanodots (from 9 to 48 nm). In the present study, the electron-phonon relaxation is measured in gold nanorods, which have different facets from those of gold nanodots.},
	isbn = {1098-0121},
	doi = {10.1103/PhysRevB.61.6086},
	author = {Link, Stephan and Burda, Clemens and Mohamed, MB and Nikoobakht, Babak and El-Sayed, Mostafa A}
}
@article {1232,
	title = {High-density femtosecond transient absorption spectroscopy of semiconductor nanoparticles. A tool to investigate surface quality},
	journal = {Pure and Applied Chemistry},
	volume = {72},
	number = {1-2},
	year = {2000},
	note = {Burda, C El-Sayed, MA1st IUPAC Workshop on Advanced Material (WAM1)Jul 14-18, 1999Hong kong, peoples r chinaIupac},
	month = {Jan-Feb},
	pages = {165-177},
	abstract = {At the high laser excitation intensities used in our experiments, more than 50 electron-hole pairs are formed in colloidal semiconductor nanoparticles used in our studies. At this density of charge carriers, new transient absorptions are observed in the femtosecond transient spectra in the 450 to 700 nm region with unresolved fast rise (<100 fs) and two decay components of 660 fs and >150 ps. The absorption at 510 nm could be quenched with the adsorption of electron accepters (e.g., benzoquinone, 1,2-naphthoquinone), whereas the low-energy transient absorption was not affected. For CdS NPs, we found that passivation eliminated most of the transient absorption. The transient absorptions are thus proposed to result from either trap-state absorption, trapped dimers (or complexes) and/or Stark-shifted exciton absorption resulting from surface electric field of the uncompensated trapped electron-hole pairs. All these possibilities require effective surface trapping at these high levels of excitation.},
	isbn = {0033-4545},
	doi = {10.1351/pac200072010165},
	author = {Burda, Clemens and El-Sayed, Mostafa A}
}
@article {1226,
	title = {How does a gold nanorod melt?},
	journal = {Journal of Physical Chemistry B},
	volume = {104},
	number = {33},
	year = {2000},
	note = {Link, S Wang, ZL El-Sayed, MA},
	month = {Aug},
	pages = {7867-7870},
	abstract = {Structural transformation of gold nanorods are investigated by high-resolution transmission electron microscopy after they have been exposed to low-energy femtosecond and nanosecond laser pulses in colloidal solution. The pulse energies were below the gold nanorod melting threshold, but allowed early stage shape transformation processes, It is found that while the as-prepared nanorods are defect-free, laser-irradiation induces point and line defects. The defects are dominated by (multiple) twins and stacking faults (planar defects), which are the precursor that drives the nanorods to convert their {110} facets into the more stable {100} and {111} facets and hence minimize their surface energy. These observations suggest that short-laser pulsed photothermal melting begins with the creation of defects inside the nanorods followed by surface reconstruction and diffusion, in contrast with the thermal melting of the rods or the bulk material, where the melting starts at the surface.},
	isbn = {1089-5647},
	doi = {10.1021/jp0011701},
	author = {Link, Stephan and Wang, Z.L. and El-Sayed, Mostafa A}
}
@article {1228,
	title = {Laser-induced shape changes of colloidal gold nanorods using femtosecond and nanosecond laser pulses},
	journal = {Journal of Physical Chemistry B},
	volume = {104},
	number = {26},
	year = {2000},
	note = {Link, S Burda, C Nikoobakht, B El-Sayed, MA},
	month = {Jul},
	pages = {6152-6163},
	abstract = {Gold nanorods have been found to change their shape after excitation with intense pulsed laser irradiation. The final irradiation products strongly depend on the energy of the laser pulse as well as on its width. We performed a series of measurements in which the excitation power was varied over the range of the output power of an amplified femtosecond laser system producing pulses of 100 fs duration and a nanosecond optical parametric oscillator (OPO) laser system having a pulse width of 7 ns. The shape transformations of the gold nanorods are followed by two techniques: (1) visible absorption spectroscopy by monitoring the changes in the plasmon absorption bands characteristic for gold nanoparticles; (2) transmission electron microscopy (TEM) in order to analyze the final shape and size distribution. While at high laser fluences (similar to 1 J cm(-2)) the gold nanoparticles fragment, a melting of the nanorods into spherical nanoparticles (nanodots) is observed when the laser energy is lowered. Upon decreasing the energy of the excitation pulse, only partial melting of the nanorods takes place. Shorter but wider nanorods are observed in the final distribution as well as a higher abundance of particles having odd shapes (bent, twisted, phi-shaped, etc.). The threshold for complete melting of the nanorods with femtosecond laser pulses is about 0.01 J cm(-2). Comparing the results obtained using the two different types of excitation sources (femtosecond vs nanosecond laser), it is found that the energy threshold for a complete melting of the nanorods into nanodots is about 2 orders of magnitude higher when using nanosecond laser pulses than with femtosecond laser pulses. This is explained in terms of the successful competitive cooling process of the nanorods when the nanosecond laser pulses are used. For nanosecond pulse excitation, the absorption of the nanorods decreases during the laser pulse because of the bleaching of the longitudinal plasmon band. In addition, the cooling of the lattice occurring on the 100 ps time scale can effectively compete with the rate of absorption in the case of the nanosecond pulse excitation but not for the femtosecond pulse excitation. When the excitation source is a femtosecond laser pulse, the involved precesses (absorption of the photons by the electrons (100 fs), heat transfer between the hot electrons and the lattice (<10 ps), melting (30 ps), and heat loss to the surrounding solvent (>100 ps) are clearly separated in time.},
	isbn = {1089-5647},
	doi = {10.1021/jp000679t},
	author = {Link, Stephan and Burda, Clemens and Nikoobakht, Babak and El-Sayed, Mostafa A}
}
@article {1224,
	title = {The {\textquoteright}lightning{\textquoteright} gold nanorods: fluorescence enhancement of over a million compared to the gold metal},
	journal = {Chemical Physics Letters},
	volume = {317},
	number = {6},
	year = {2000},
	note = {Mohamed, MB Volkov, V Link, S El-Sayed, MA},
	month = {Feb},
	pages = {517-523},
	abstract = {Gold nanorods capped with micelles and having an aspect ratio of 2.0-5.4 are found to fluoresce with a quantum yield which is over a million times that of the metal. For rods of the same width, the yield is found to increase quadratically while the wavelength maximum increases linearly with the length. We assign this emission to the electron and hole interband recombination. The increase in the emission yield results from the enhancement effect of the incoming and outgoing electric fields via coupling to the surface plasmon resonance in the rods. This is similar to the previously proposed fluorescence and the Raman enhancement on noble metal rough surfaces. (C) 2000 Published by Elsevier Science B.V. All rights reserved.},
	isbn = {0009-2614},
	doi = {10.1016/s0009-2614(99)01414-1},
	author = {Mohamed, MB and Volkov, V. V. and Link, Stephan and El-Sayed, Mostafa A}
}
@article {857,
	title = {Origin of emission from porous silicon: Temperature-dependence correlation with proton conductivity},
	journal = {Physical Review B},
	volume = {62},
	year = {2000},
	pages = {16595},
	publisher = {APS},
	abstract = {The excitation, emission, and Fourier transform infrared (FTIR) spectra of freshly prepared and aged porous silicon (PS) are examined. The effects of aging and temperature changing on the emission and excitation spectra of fresh and aged PS samples is also studied. Aging in air is found to result in a redshift in the emission spectrum, but a blueshift in the excitation spectrum. Increasing the temperatures leads to a general decrease in the emission intensities of both samples: however, the green emission of fresh sample shows an unusually large and sudden increase in its intensity at the same temperature at which the proton conductivity in the silicon wafer increases. The temperature dependence of the O-H vibration intensity of silicon wafers shows a sudden decrease at that temperature. These results are consistent with a model in which the excitation leads to the formation of exciton in the confined nanostructure, and the formation of electron and hole that are trapped by surface traps, whose nature is dependent on the chemical composition of the surface (and thus its age). These conclusions are confirmed by the results of the FTIR spectra of the two samples, the temperature dependence of the emission, and its correlation with the proton conductivity in the fresh PS.},
	doi = {10.1103/PhysRevB.62.16595},
	url = {http://link.aps.org/doi/10.1103/PhysRevB.62.16595},
	author = {Zou, Bingsuo and Wang, Jianping and Liu, C. and Zhang, J.Z. and El-Sayed, Mostafa A}
}
@article {1225,
	title = {Probing the primary event in the photocycle of photoactive yellow protein using photochemical hole-burning technique},
	journal = {Photochemistry and Photobiology},
	volume = {72},
	number = {5},
	year = {2000},
	note = {Mascianglioli, T Devanathan, S Cusanovich, MA Tollin, G El-Sayed, MA},
	month = {Nov},
	pages = {639-644},
	abstract = {Photochemical hole-burning spectroscopy was used to study the excited-state electronic structure of the 4-hydroxycinnamyl chromophore in photoactive yellow protein (PYP), This system Is known to undergo a trans-to-cis isomerization process on a femtosecond-to-picosecond time scale, similar to membrane-bound rhodopsins, and is characterized by a broad featureless absorbance at 446 nm, Resolved vibronic structure was observed for the hole-burned spectra obtained when PYP in phosphate buffer at pH 7 was frozen at low temperature and irradiated with narrow bandwidth laser light at 331 nm, The approximate homogeneous width of 752 cm(-1) could be calculated From the deconvolution of the hole-burned spectra leading to an estimated dephasing time of similar to 14 fs for the PYP excited-state structure. The resolved vibronic structure also enabled us to obtain an estimated change in the C=C stretching frequency, from 1663 cm(-1) in the ground state to similar to 1429 cm(-1) upon photoexcitation. The results obtained allowed us to speculate about the excited-state structure of PYP, We discuss the data for PYP in relation to the excited-state model proposed for the photosynthetic membrane protein bacteriorhodopsin, and use it to explain the primary event in the function of photoactive biological protein systems. Photoexcitation was also carried out at 475 nm, The vibronic structure obtained was quite different both in terms of the frequencies and Franck-Condon envelope. The origin of this spectrum was tentatively assigned.},
	isbn = {0031-8655},
	doi = {10.1562/0031-8655(2000)072<0639:ptpeit>2.0.co;2},
	author = {Mascianglioli, T. and Devanathan, S. and Cusanovich, M. A. and Tollin, G. and El-Sayed, Mostafa A}
}
@article {1221,
	title = {Proton polarizability of hydrogen-bonded network and its role in proton transfer in bacteriorhodopsin},
	journal = {Journal of Physical Chemistry A},
	volume = {104},
	number = {18},
	year = {2000},
	note = {Wang, JP El-Sayed, MA},
	month = {May},
	pages = {4333-4337},
	abstract = {Room-temperature time-resolved step-scan Fourier Transform Infrared (FTIR) spectroscopy has been used to study the photocycle of native bacteriorhodopsin (bR) suspension in both H2O and D2O. The kinetics of the retinal isomerization, and that of the protonation/deprotonation of the proton acceptor, Asp85, are compared in the mu s to Ins time domain. It is found that hydrogen/deuterium (H/D) isotope exchange does not significantly affect the kinetics of the retinal isomerization and relaxation processes. However, the protonation/deprotonation processes of Asp85 COO- become slower in D2O. We also studied the kinetics of the continuum absorbance change in the 1850-1800 cm(-1) frequency region, which has previously been proposed to correspond to the absorption of the delocalized proton that is involved in the proton transport to the surface during the photocycle. An H/D isotope shift of the frequency range of this continuum absorbance has been confirmed by the observation that the band in the 1850-1800 cm(-1) disappears in the photocycle of bR in D2O. These results could support the previous proposal that the intramolecular proton release pathway consists of an H-bonded network. Our results also suggest that the two independent processes, the transfer of a proton from the Schiff base to Asp85 and the release of a different proton to the extracellular surface, are closely coupled events.},
	isbn = {1089-5639},
	doi = {10.1021/jp994460u},
	author = {Wang, Jianping and El-Sayed, Mostafa A}
}
@article {1223,
	title = {Self-assembly of gold nanorods},
	journal = {Journal of Physical Chemistry B},
	volume = {104},
	number = {36},
	year = {2000},
	note = {Nikoobakht, B Wang, ZL El-Sayed, MA},
	month = {Sep},
	pages = {8635-8640},
	abstract = {Self-assembly of gold nanorods (NRs) with aspect ratio of similar to 4.6 (12 nm in diameter and 50-60 nm in length) has been studied using transmission electron microscopy (TEM). Under appropriate conditions such as nanoparticle concentration, solvent evaporation, narrow size distribution, ionic strength, and surfactant concentration of the parent solution, gold nanorods assemble into one-, two-, and three-dimensional structures. Some of the three-dimensional assemblies extend to superlattices of NRs. The translation and orientation symmetries of the self-assembled structures are determined. The factors affecting the formation of the ordered self-assembly are discussed.},
	isbn = {1089-5647},
	doi = {10.1021/jp001287p},
	author = {Nikoobakht, Babak and Wang, Z.L. and El-Sayed, Mostafa A}
}
@article {1227,
	title = {Shape and size dependence of radiative, non-radiative and photothermal properties of gold nanocrystals},
	journal = {International Reviews in Physical Chemistry},
	volume = {19},
	number = {3},
	year = {2000},
	note = {Link, S El-Sayed, MA},
	month = {Jul-Sep},
	pages = {409-453},
	abstract = {Driven by the search for new materials with interesting and unique properties and also by the fundamental question of how atomic and molecular physical behaviour develops with increasing size, the field of nanoparticle research has grown immensely in the last two decades. Partially for these reasons, colloidal solutions of metallic (especially silver and gold) nanoparticles have long fascinated scientists because of their very intense colours. The intense red colour of colloidal gold nanoparticles is due to their surface plasmon absorption. This article describes the physical origin of the surface plasmon absorption in gold nanoparticles with emphasis on the Mie and also the MaxweIl-Garnett theory and reviews the effects of particle size and shape on the resonance condition. A better understanding of the relationship between the optical absorption spectrum (in particular, the plasmon resonance) and such particle properties as its dimensions or surrounding environment can prove fruitful for the use of the plasmon absorption as an analytical tool. The plasmon resonance has also had a great impact on the Raman spectrum of surface-adsorbed molecules and a large enhancement of the fluorescence quantum yield of gold nanorods is observed. Furthermore, following the changes in the plasmon absorption induced by excitation (heating) with ultrashort laser pulses allows one to monitor the electron dynamics (electron-electron and electron-phonon interactions) in real time, which is important in understanding such fundamental questions regarding the thermal and electrical conductivity of these nanoparticles. Very intense heating with laser pulses leads to structural changes of the nanoparticles (nuclear rearrangements in the form of melting and fragmentation).},
	isbn = {0144-235X},
	doi = {10.1080/01442350050034180},
	author = {Link, Stephan and El-Sayed, Mostafa A}
}
@article {1220,
	title = {Surface reconstruction of the unstable {110} surface in gold nanorods},
	journal = {Journal of Physical Chemistry B},
	volume = {104},
	number = {23},
	year = {2000},
	note = {Wang, ZL Gao, RP Nikoobakht, B El-Sayed, MA},
	month = {Jun},
	pages = {5417-5420},
	abstract = {Gold nanorods prepared electrochemically and capped in micelles are examined using high-resolution transmission electron microscopy (TEM), It is found that they have an axial growth direction of [001] and have surfaces made of {100} and the unstable {110} facets. A detailed examination of the defect sites of both of these facets shows that while the defective regions of the stable {100} facets show atom-height steps with no reconstruction, the less stable higher energy {110} surfaces show missing-row reconstruction. The role of micelles in stabilizing the {110} facet in the gold nanorod is briefly discussed.},
	isbn = {1089-5647},
	doi = {10.1021/jp000800w},
	author = {Wang, Z.L. and Gao, R. P. and Nikoobakht, Babak and El-Sayed, Mostafa A}
}
@article {1231,
	title = {Suzuki cross-coupling reactions catalyzed by palladium nanoparticles in aqueous solution},
	journal = {Organic Letters},
	volume = {2},
	number = {15},
	year = {2000},
	note = {Li, Y Hong, XM Collard, DM El-Sayed, MA},
	month = {Jul},
	pages = {2385-2388},
	abstract = {[GRAPHICS] Palladium nanoparticles stabilized by poly(N-vinyl-2-pyrrolidone) (PVP) are efficient catalysts for the Suzuki reactions in aqueous medium. The time dependence of the fluorescence intensity of the biphenyl product in the reaction between iodobenzene and phenylboronic acid is used to determine the initial rate of the catalytic reaction. The initial rate depends linearly on the concentration of Pd catalyst, suggesting that the catalytic reaction occurs on the surface of the Pd nanoparticles.},
	isbn = {1523-7060},
	doi = {10.1021/ol0061687},
	author = {Li, Y. and Hong, X. M. and Collard, D. M. and El-Sayed, Mostafa A}
}
@article {1240,
	title = {Alloy formation of gold-silver nanoparticles and the dependence of the plasmon absorption on their composition},
	journal = {Journal of Physical Chemistry B},
	volume = {103},
	number = {18},
	year = {1999},
	note = {Link, S Wang, ZL El-Sayed, MA},
	month = {May},
	pages = {3529-3533},
	abstract = {Gold-silver alloy nanoparticles with varying mole fractions are prepared in aqueous solution by the co-reduction of chlorauric acid HAuCl4 and silver nitrate AgNO3 with sodium citrate. As the optical absorption spectra of their solutions show only one plasmon absorption it is concluded that mixing of gold and silver leads to a homogeneous formation of alloy nanoparticles. The maximum of the plasmon band blue-shifts linearly with increasing silver content. This fact cannot be explained by a simple linear combination of the dielectric constants of gold and silver within the Mie theory. On the other hand, the extinction coefficient is found to decrease exponentially rather than linearly with increasing gold mole fraction x(Au). Furthermore, the size distribution of the alloy nanoparticles is examined using transmission electron microscopy (TEM). High-resolution TEM (HRTEM) also confirms the formation of homogeneous gold-silver alloy nanocrystals.},
	isbn = {1089-5647},
	doi = {10.1021/jp990387w},
	author = {Link, Stephan and Wang, Z.L. and El-Sayed, Mostafa A}
}
@article {1236,
	title = {Comparison between the polarized Fourier-transform infrared spectra of aged porous silicon and amorphous silicon dioxide films on Si (100) surface},
	journal = {Journal of Molecular Structure},
	volume = {508},
	number = {1-3},
	year = {1999},
	note = {Wang, JP Zou, BS El-Sayed, MA},
	month = {Sep},
	pages = {87-96},
	abstract = {The s- and p-polarized Fourier transform infrared spectra were measured for an aged porous silicon (PS) film on Si (100) surface. The asymmetric stretching and symmetric stretching modes as well as the bending or rocking mode of the Si-O-Si group are studied. The deconvoluted spectra in Si-O-Si asymmetric stretching frequency region at different polarization directions show two pairs of vibrational modes, and can be assigned to the longitudinal-optic (LO) and transverse-optic (TO) pair of the corresponding vibrational modes. The smaller LO-TO pair splitting, the broader bandwidth, and the lower polarization ratio of the PS vibration bands as compared with those observed in an a-SiO2 film on Si wafer, suggest a less ordered SiO2 structure and a shorter range of coulombic interaction in PS. (C) 1999 Elsevier Science B.V. All rights reserved.},
	isbn = {0022-2860},
	doi = {10.1016/s0022-2860(99)00003-4},
	author = {Wang, Jianping and Zou, Bingsuo and El-Sayed, Mostafa A}
}
@article {1235,
	title = {Crystallographic facets and shapes of gold nanorods of different aspect ratios},
	journal = {Surface Science},
	volume = {440},
	number = {1-2},
	year = {1999},
	note = {Wang, ZL Mohamed, MB Link, S El-Sayed, MA},
	month = {Oct},
	pages = {L809-L814},
	abstract = {Crystal structures of gold nanorods synthesized electrochemically using micelles as a capping material have been studied by high-resolution transmission electron microscopy. Short gold nanorods with aspect ratios of 3-7 are enclosed mainly by (100) and (110) facets and their axial growth direction is [001], whereas long gold nanorods of aspect ratios 20-35 are dominated by (111) and (110) facets and their growth axial direction is (112). The short rods are the dominant constituents, whereas the long rods are observed occasionally. Spherical-like Au particles with equivalent mass to the short rods are dominated by (111) and (100) facets with shapes of truncated octahedra, icosahedra and decahedra. The unique (110) facets of Au nanorods are expected to have interesting surface properties. (C) 1999 Elsevier Science B.V. All rights reserved.},
	isbn = {0039-6028},
	doi = {10.1016/s0039-6028(99)00865-1},
	author = {Wang, Z.L. and Mohamed, MB and Link, Stephan and El-Sayed, Mostafa A}
}
@article {1234,
	title = {Effect of different capping environments on the optical properties of CdS nanoparticles in reverse micelles},
	journal = {International Journal of Quantum Chemistry},
	volume = {72},
	number = {4},
	year = {1999},
	note = {Zou, BS Little, RB Wang, JP El-Sayed, MA},
	month = {Apr},
	pages = {439-450},
	abstract = {CdS(E = 2.5 eV) nanoparticles were synthesized in reversed micelles and capped with materials of different band gaps and charge compensation ability: Cd(OH)(2) (4.0 eV), ZnS (3.2 eV), and CdO (2.3 eV). The preparations allowed the examination and comparison of the efficiencies of confinement of the electron and hole by the various capping materials. The absorption and emission spectra of the capped CdS nanoparticles suggest the following: (1) Efficient capping and strong quantum confinement are observed for CdS particles of small size (< 3.8 nm), showing well-resolved photoexcitation spectra; (2) the confinement efficiency improves with capping thickness; (3) although ZnS has smaller band gap than Cd(OH)(2), it was more efficient in surface-charge compensation and it is the best capping agent of the three materials; and (4) the similar band gaps of CdO and CdS resulted spectroscopically in strong mixing between the excited states of these materials. (C) 1999 John Wiley \& Sons, Inc.},
	isbn = {0020-7608},
	doi = {10.1002/(sici)1097-461x(1999)72:4<439::aid-qua27>3.0.co;2-q},
	author = {Zou, Bingsuo and Little, Reginald and Wang, Jianping and El-Sayed, Mostafa A}
}
@article {1247,
	title = {The effect of low and high temperature anneals on the hydrogen content and passivation of Si surface coated with SiO2 and SiN films},
	journal = {Journal of the Electrochemical Society},
	volume = {146},
	number = {5},
	year = {1999},
	note = {Ebong, A Doshi, P Narasimha, S Rohatgi, A Wang, J El-Sayed, MA},
	month = {May},
	pages = {1921-1924},
	abstract = {A detailed comparison of the passivation quality and its dependence on the low and high temperature anneals is presented for various promising Si surface passivation schemes. The passivation schemes investigated in this study include: conventional furnace oxide (CFO), rapid thermal oxide (RTO), belt line oxide (BLO), plasma deposited oxide (PDO), SiN deposited by plasma enhanced chemical vapor deposition (PECVD), CFO/SiN, RTO/SiN, BLO/SiN, PDO/SiN, and RTO/PDO. Passivated low resistivity (1 Ohm cm) p-type silicon samples were subjected to three annealing treatments: (a) 400 degrees C in forming gas (FGA), (b) 730 degrees C in air, and (c) 850 degrees C in air, to simulate heat-treatments, which are typically used for contact anneal, front ohmic contacts, and back surface field formation, respectively, for screen printed silicon solar cells. It is found that the passivation quality of PDO, SiN, RTO, and CFO single layers improves significantly after the 400 degrees C FGA and 730 degrees C thermal cycles with RTO resulting in the lowest surface recombination velocities (S-eff) of 154 and 405 cm/s, respectively. Silicon wafers coated with belt oxide (BLO and BLO/SiN) did not show any improvement in S-eff, which remained at 5000 cm/s due to the inferior quality of BLO formed in compressed air. The oxide/ nitride stack passivation is found to be far superior to single-layer passivation resulting in S-eff Of 70 cm/s for the RTO/SiN scheme after the two high temperature anneals (850 and 730 degrees C). The hydrogen concentration measurements by Fourier transform infrared spectroscopy show a greater decrease in the hydrogen content in the annealed RTO/SiN stack compared to the as-deposited SiN single layer after the 730 and 850 degrees C anneals. A combination of reduced hydrogen content and very low S-eff in the RTO/SiN stack suggests that the release of hydrogen from SiN during the anneal further passivates the RTO/Si interface underneath. (C) 1999 The Electrochemical Society. S0013-4651(98)08-117-8. All rights reserved.},
	isbn = {0013-4651},
	doi = {10.1149/1.1391866},
	author = {Ebong, A. and Doshi, P. and Narasimha, S. and Rohatgi, A. and Wang, Jianping and El-Sayed, Mostafa A}
}
@article {1244,
	title = {Electron dynamics in gold and gold-silver alloy nanoparticles: The influence of a nonequilibrium electron distribution and the size dependence of the electron-phonon relaxation},
	journal = {Journal of Chemical Physics},
	volume = {111},
	number = {3},
	year = {1999},
	note = {Link, S Burda, C Wang, ZL El-Sayed, MA},
	month = {Jul},
	pages = {1255-1264},
	abstract = {Electron dynamics in gold nanoparticles with an average diameter between 9 and 48 nm have been studied by femtosecond transient absorption spectroscopy. Following the plasmon bleach recovery after low power excitation indicates that a non-Fermi electron distribution thermalizes by electron-electron relaxation on a time scale of 500 fs to a Fermi distribution. This effect is only observed at low excitation power and when the electron distribution is perturbed by mixing with the intraband transitions within the conduction band (i.e., when the excitation wavelength is 630 or 800 nm). However, exciting the interband transitions at 400 nm does not allow following the early electron thermalization process. Electron thermalization with the lattice of the nanoparticle by electron-phonon interactions occurs within 1.7 ps under these conditions, independent of the excitation wavelength. In agreement with the experiments, simulations of the optical response arising from thermalized and nonthermalized electron distributions show that a non-Fermi electron distribution leads to a less intense bleach of the plasmon absorption. Furthermore, the difference between the response from the two electron distributions is greater for small temperature changes of the electron gas (low excitation powers). No size dependence of the electron thermalization dynamics is observed for gold nanoparticles with diameters between 9 and 48 nm. High-resolution transmission electron microscopy (HRTEM) reveals that these gold nanoparticles possess defect structures. The effect of this on the electron-phonon relaxation processes is discussed. 18 nm gold-silver alloy nanoparticles with a gold mole fraction of 0.8 are compared to 15 nm gold nanoparticles. While mixing silver leads to a blue-shift of the plasmon absorption in the ground-state absorption spectrum, no difference is observed in the femtosecond dynamics of the system. (C) 1999 American Institute of Physics. [S0021-9606(99)71427-3].},
	isbn = {0021-9606},
	doi = {10.1063/1.479310},
	author = {Link, Stephan and Burda, Clemens and Wang, Z.L. and El-Sayed, Mostafa A}
}
@article {1291,
	title = {Electron Shuttling Across the Interface of CdSe Nanoparticles Monitored by Femtosecond Laser Spectroscopy},
	journal = {The Journal of Physical Chemistry B},
	volume = {103},
	year = {1999},
	note = {doi: 10.1021/jp9843050},
	month = {1999},
	pages = {1783 - 1788},
	publisher = {American Chemical Society},
	abstract = {The formation and decay of the optical hole (bleach) for 4 nm CdSe nanoparticles (NPs) with adsorbed electron acceptors (1,4-benzoquinone and 1,2-naphthoquinone) and the rise and decay of the reduced electron acceptors formed after interfacial electron transfer from the CdSe NPs were investigated by femtosecond laser spectroscopy. The ultrashort (200?400 fs) rise times of the bleach at the band-gap energy of the CdSe NP as well as of the acceptor radical anion are found to increase with increasing the excitation energy. This suggests that the electron transfer from the CdSe NP to the quinone electron acceptor occurs after thermalization of the excited hot electrons. The decay times of the transient absorption for the electron acceptor radical anions are found to be comparable to that of the CdSe NP bleach recovery time (3 ps). This suggests that the surface quinones shuttle the electron from the conduction band to the valence band of the excited NP. We contrast this behavior with the excited-state dynamics of the recently investigated CdS?MV2+ system in which the electron acceptor does not shuttle the accepted electron back to the hole in CdS.The formation and decay of the optical hole (bleach) for 4 nm CdSe nanoparticles (NPs) with adsorbed electron acceptors (1,4-benzoquinone and 1,2-naphthoquinone) and the rise and decay of the reduced electron acceptors formed after interfacial electron transfer from the CdSe NPs were investigated by femtosecond laser spectroscopy. The ultrashort (200?400 fs) rise times of the bleach at the band-gap energy of the CdSe NP as well as of the acceptor radical anion are found to increase with increasing the excitation energy. This suggests that the electron transfer from the CdSe NP to the quinone electron acceptor occurs after thermalization of the excited hot electrons. The decay times of the transient absorption for the electron acceptor radical anions are found to be comparable to that of the CdSe NP bleach recovery time (3 ps). This suggests that the surface quinones shuttle the electron from the conduction band to the valence band of the excited NP. We contrast this behavior with the excited-state dynamics of the recently investigated CdS?MV2+ system in which the electron acceptor does not shuttle the accepted electron back to the hole in CdS.},
	isbn = {1520-6106},
	doi = {doi: 10.1021/jp9843050},
	url = {http://dx.doi.org/10.1021/jp9843050},
	author = {Burda, Clemens and Green, T.C. and Link, Stephan and El-Sayed, Mostafa A}
}
@article {1245,
	title = {How long does it take to melt a gold nanorod? A femtosecond pump-probe absorption spectroscopic study},
	journal = {Chemical Physics Letters},
	volume = {315},
	number = {1-2},
	year = {1999},
	note = {Link, S Burda, C Nikoobakht, B El-Sayed, MA},
	month = {Dec},
	pages = {12-18},
	abstract = {Using pump-probe femtosecond transient absorption spectroscopy, we determined the rate of the bleach of absorption around 700-800 nm due to the longitudinal surface plasmon band of gold nanorods. Using TEM of the spotted, completely irradiated solutions suggest that the dominant products of the photothermal conformation of the rods are spheres of comparable volume. This lead to the conclusion that the melting of the rods is at least 30-35 ps, independent of the power used (5-20 mu J) or the nanorod aspect ratio (1.9-3.7). (C) 1999 Elsevier Science B.V. All rights reserved.},
	isbn = {0009-2614},
	doi = {10.1016/s0009-2614(99)01214-2},
	author = {Link, Stephan and Burda, Clemens and Nikoobakht, Babak and El-Sayed, Mostafa A}
}
@article {1246,
	title = {Laser photothermal melting and fragmentation of gold nanorods: Energy and laser pulse-width dependence},
	journal = {Journal of Physical Chemistry A},
	volume = {103},
	number = {9},
	year = {1999},
	note = {Link, S Burda, C Mohamed, MB Nikoobakht, B El-Sayed, MA},
	month = {Mar},
	pages = {1165-1170},
	abstract = {We studied the shape transformation (by use of TEM and optical absorption spectroscopy) of gold nanorods in micellar solution by exposure to laser pulses of different pulse width (100 fs and 7 ns) and different energies (mu J to mJ) at 800 nm, where the longitudinal surface plasmon oscillation of the nanorods absorb. At moderate energies, the femtosecond irradiation melts the nanorods to near spherical particles of comparable volumes while the nanosecond pulses fragment them to smaller near-spherical particles. At high energies, fragmentation is also observed for the femtosecond irradiation. A mechanism involving the rate of energy deposition as compared to the rate of electron-phonon and phonon-phonon relaxation processes is proposed to determine the final fate of the laser-exposed nanorods, i.e., melting or fragmentation.},
	isbn = {1089-5639},
	doi = {10.1021/jp983141k},
	author = {Link, Stephan and Burda, Clemens and Mohamed, MB and Nikoobakht, Babak and El-Sayed, Mostafa A}
}
@article {1248,
	title = {New transient absorption observed in the spectrum of colloidal CdSe nanoparticles pumped with high-power femtosecond pulses},
	journal = {Journal of Physical Chemistry B},
	volume = {103},
	number = {49},
	year = {1999},
	note = {Burda, C Link, S Green, TC El-Sayed, MA},
	month = {Dec},
	pages = {10775-10780},
	abstract = {The power dependence of the transient absorption spectrum of CdSe nanoparticle colloids with size distribution of 4.0 +/- 0.4 nm diameter is studied with femtosecond pump-probe techniques. At the lowest pump laser power, the absorption bleaching (negative spectrum) characteristic of the exciton spectrum is observed with maxima at 560 and 480 nm, As the pump laser power increases, two new transient absorptions at 510 and 590 nm with unresolved fast rise (<100 fs) and long decay times (much greater than 150 ps) are observed. The energy of each of the positive absorption is red shifted from that of the bleach bands by similar to 120 meV. The origin of this shift is discussed in terms of the effect of the internal electric field of the many electron-hole pairs formed within the quantum dot at the high pump intensity, absorption from a metastable excited state or the formation of biexcitons.},
	isbn = {1089-5647},
	doi = {10.1021/jp991503y},
	author = {Burda, Clemens and Link, Stephan and Green, T.C. and El-Sayed, Mostafa A}
}
@article {834,
	title = {Simulation of the Optical Absorption Spectra of Gold Nanorods as a Function of Their Aspect Ratio and the Effect of the Medium Dielectric Constant},
	journal = {The Journal of Physical Chemistry B },
	volume = {103},
	year = {1999},
	note = {doi: 10.1021/jp990183f},
	month = {1999},
	pages = {3073 - 3077},
	publisher = {American Chemical Society},
	abstract = {Gold nanorods with different aspect ratios are prepared in micelles by the electrochemical method and their absorption spectra are modeled by theory. Experimentally, a linear relationship is found between the absorption maximum of the longitudinal plasmon resonance and the mean aspect ratio as determined from TEM. It is shown here that such a linear dependence is also predicted theoretically. However, calculations also show that the absorption maximum of the longitudinal plasmon resonance depends on the medium dielectric constant in a linear fashion for a fixed aspect ratio. Attempts to fit the calculations to the experimental values indicate that the medium dielectric constant has to vary with the aspect ratio in a nonlinear way. Chemically, this suggests that the structure of the micelle capping the gold nanorods is size dependent. Furthermore, comparison with the results obtained for rods of different aspect ratios made by systematic thermal decomposition of the long rods further suggests that the medium dielectric constant is also temperature dependent. This is attributed to thermal annealing of the structure of the micelles around the nanorods.Gold nanorods with different aspect ratios are prepared in micelles by the electrochemical method and their absorption spectra are modeled by theory. Experimentally, a linear relationship is found between the absorption maximum of the longitudinal plasmon resonance and the mean aspect ratio as determined from TEM. It is shown here that such a linear dependence is also predicted theoretically. However, calculations also show that the absorption maximum of the longitudinal plasmon resonance depends on the medium dielectric constant in a linear fashion for a fixed aspect ratio. Attempts to fit the calculations to the experimental values indicate that the medium dielectric constant has to vary with the aspect ratio in a nonlinear way. Chemically, this suggests that the structure of the micelle capping the gold nanorods is size dependent. Furthermore, comparison with the results obtained for rods of different aspect ratios made by systematic thermal decomposition of the long rods further suggests that the medium dielectric constant is also temperature dependent. This is attributed to thermal annealing of the structure of the micelles around the nanorods.},
	isbn = {1520-6106},
	url = {http://dx.doi.org/10.1021/jp990183f},
	author = {Link, Stephan and Mohamed, MB and El-Sayed, Mostafa A}
}
@article {1241,
	title = {Simulation of the optical absorption spectra of gold nanorods as a function of their aspect ratio and the effect of the medium dielectric constant},
	journal = {Journal of Physical Chemistry B},
	volume = {103},
	number = {16},
	year = {1999},
	note = {Link, S Mohamed, MB El-Sayed, MA},
	month = {Apr},
	pages = {3073-3077},
	abstract = {Gold nanorods with different aspect ratios are prepared in micelles by the electrochemical method and their absorption spectra are modeled by theory. Experimentally, a linear relationship is found between the absorption maximum of the longitudinal plasmon resonance and the mean aspect ratio as determined from TEM. It is shown here that such a linear dependence is also predicted theoretically. However, calculations also show that the absorption maximum of the longitudinal plasmon resonance depends on the medium dielectric constant in a linear fashion for a fixed aspect ratio. Attempts to fit the calculations to the experimental values indicate that the medium dielectric constant has to vary with the aspect ratio in a nonlinear way. Chemically, this suggests that the structure of the micelle capping the gold nanorods is size dependent. Furthermore, comparison with the results obtained for rods of different aspect ratios made by systematic thermal decomposition of the long rods further suggests that the medium dielectric constant is also temperature dependent. This is attributed to thermal annealing of the structure of the micelles around the nanorods.},
	isbn = {1089-5647},
	doi = {10.1021/jp990183f},
	author = {Link, Stephan and Mohamed, MB and El-Sayed, Mostafa A}
}
@article {1243,
	title = {Size and temperature dependence of the plasmon absorption of colloidal gold nanoparticles},
	journal = {Journal of Physical Chemistry B},
	volume = {103},
	number = {21},
	year = {1999},
	note = {Link, S El-Sayed, MA},
	month = {May},
	pages = {4212-4217},
	abstract = {The size and temperature dependence of the plasmon absorption is studied for 9, 15, 22, 48, and 99 nm gold nanoparticles in aqueous solution. The plasmon bandwidth is found to follow the predicted behavior as it increases with decreasing size in the intrinsic size region (mean diameter smaller than 25 nm), and also increases with increasing size in the extrinsic size region (mean diameter larger than 25 nm). Because of this pronounced size effect a homogeneous size distribution and therefore a homogeneous broadening of the plasmon band is concluded for all the prepared gold nanoparticle samples. By applying a simple two-level model the dephasing time of the coherent plasmon oscillation is calculated and found to be less than 5 fs. Furthermore, the temperature dependence of the plasmon absorption is examined. A small temperature effect is observed. This is consistent with the fact that the dominant electronic dephasing mechanism involves electron-electron interactions rather than electron-phonon coupling.},
	isbn = {1089-5647},
	doi = {10.1021/jp984796o},
	author = {Link, Stephan and El-Sayed, Mostafa A}
}
@article {1242,
	title = {Spectral properties and relaxation dynamics of surface plasmon electronic oscillations in gold and silver nanodots and nanorods},
	journal = {Journal of Physical Chemistry B},
	volume = {103},
	number = {40},
	year = {1999},
	note = {Link, S El-Sayed, MA},
	month = {Oct},
	pages = {8410-8426},
	abstract = {The field of nanoparticle research has drawn much attention in the past decade as a result of the search for new materials. Size confinement results in new electronic and optical properties, possibly suitable for many electronic and optoelectronic applications. A characteristic feature of noble metal nanoparticles is the strong color of their colloidal solutions, which is caused by the surface plasmon absorption. This article describes our studies of the properties of the surface plasmon absorption in metal nanoparticles that range in size between 10 and 100 nm. The effects of size, shape, and composition on the plasmon absorption maximum and its bandwidth are discussed. Furthermore, the optical response of the surface plasmon absorption due to excitation with femtosecond laser pulses allowed us to follow the electron dynamics (electron-electron and electron-phonon scattering) in these metal nanoparticles. It: is found that the electron-phonon relaxation processes in nanoparticles, which are smaller than the electron mean free path, are independent of their size or shape. Intense laser heating of the electrons in these particles is also found to cause a shape transformation (photoisomerization of the rods into spheres or fragmentation), which depends on the laser pulse energy and pulse width.},
	isbn = {1089-5647},
	doi = {10.1021/jp9917648},
	author = {Link, Stephan and El-Sayed, Mostafa A}
}
@article {1238,
	title = {Temperature jump-induced secondary structural change of the membrane protein bacteriorhodopsin in the premelting temperature region: A nanosecond time-resolved Fourier transform infrared study},
	journal = {Biophysical Journal},
	volume = {76},
	number = {5},
	year = {1999},
	note = {Wang, JP El-Sayed, MA},
	month = {May},
	pages = {2777-2783},
	abstract = {The secondary structural changes of the membrane protein, bacteriorhodopsin, are studied during the premelting reversible transition by using laser-induced temperature jump technique and nanosecond time-resolved Fourier transform infrared spectroscopy. The helical structural changes are triggered by using a 15 degrees C temperature jump induced from a preheated bacteriorhodopsin in D2O solution at a temperature of 72 degrees C. The structural transition from alpha(II)- to alpha(I)-helices is observed by following the change in the frequency of the amide I band from 1667 to 1651 cm(-1) and the shift in the frequency of the amide II vibration from 1542 cm(-1) to 1436 cm(-1) upon H/D exchange. It is found that although the amide I band changes its frequency on a time scale of <100 ns, the H/D exchange shifts the frequency of the amide II band and causes a complex changes in the 1651-1600 cm(-1) and 1530-1430 cm(-1) frequency region on a longer time scale (>300 ns). Our result suggests that in this "premelting transition" temperature region of bacterioriorhodopsin, an intrahelical conformation conversion of the alpha(II) to alpha(I) leads to the exposure of the hydrophobic region of the protein to the aqueous medium.},
	isbn = {0006-3495},
	author = {Wang, Jianping and El-Sayed, Mostafa A}
}
@article {1239,
	title = {Temperature-dependent size-controlled nucleation and growth of gold nanoclusters},
	journal = {Journal of Physical Chemistry A},
	volume = {103},
	number = {49},
	year = {1999},
	note = {Mohamed, MB Wang, ZL El-Sayed, MA},
	month = {Dec},
	pages = {10255-10259},
	abstract = {The electrochemical method of synthesis of gold nanorods in micelles gives substrate solutions that upon spotting and heating on a transmission electron microscope (TEM) substrate result in the nucleation and growth of small gold nanoclusters of narrow size distribution. The size of the nanoclusters, and not their numbers, is found to increased with increasing final temperature to which the substrate is heated. The data are fitted to a mechanism, based on Ostwald ripening in which atomic gold diffusion followed by nucleation on nucleating sites leads to the formation of these small clusters.},
	isbn = {1089-5639},
	doi = {10.1021/jp9919720},
	author = {Mohamed, MB and Wang, Z.L. and El-Sayed, Mostafa A}
}
@article {1237,
	title = {Time-resolved Fourier-transform infrared and visible luminescence spectroscopy of photoexcited porous silicon},
	journal = {Physical Review B},
	volume = {59},
	number = {7},
	year = {1999},
	note = {Wang, JP Song, L Zou, BS El-Sayed, MA},
	month = {Feb},
	pages = {5026-5031},
	abstract = {In order to identify the luminescent centers in aged porous silicon, both the time-resolved vibration spectra in the 750-2000-cm(-1) region and the visible luminescence spectra are studied for the same sample in the 0-440-mu s time domain. Laser excitation gives rise to emission characteristics of the porous silicon as well as strong bleach in the infrared spectrum in the region of the ground-stale silicon-oxygen stretching vibration frequencies at 1100 and 1235 cm(-1). In addition, new transient absorption bands appear in this region as a result of the laser excitation. Three characteristic Lifetimes in the decay of the bleach band at 1235 cm(-1) are observed on the 1-, 10-, and 100-mu s time scale. These are similar to the observed decay times of the photoluminescence from porous silicon. These results suggest that the emitting centers in aged porous silicon are trapped excitation sites in an inhomogeneously defected oxidized silicon surface. [S0163-1829(99)09207-3].},
	isbn = {0163-1829},
	doi = {10.1103/PhysRevB.59.5026},
	author = {Wang, Jianping and Song, Li and Zou, Bingsuo and El-Sayed, Mostafa A}
}
@article {1250,
	title = {Application of liquid waveguide to Raman spectroscopy in aqueous solution},
	journal = {Applied Spectroscopy},
	volume = {52},
	number = {10},
	year = {1998},
	note = {Song, L Liu, SY Zhelyaskov, V El-Sayed, MA},
	month = {Oct},
	pages = {1364-1367},
	isbn = {0003-7028},
	author = {Song, Li and Liu, S. Y. and Zhelyaskov, V. and El-Sayed, Mostafa A}
}
@article {1257,
	title = {Charge separation effects on the rate of nonradiative relaxation processes in quantum dots quantum well heteronanostructures},
	journal = {Journal of Physical Chemistry A},
	volume = {102},
	number = {33},
	year = {1998},
	note = {Little, RB Burda, C Link, S Logunov, S El-Sayed, MA},
	month = {Aug},
	pages = {6581-6584},
	abstract = {Using time-resolved optical hole (oh)-burning techniques with femtosecond lasers, the time dependence of the spectral diffusion of the oh is examined for both the CdS quantum dot (QD) and the CdS/HgS/CdS quantum dot quantum well (QDQW) nanoparticles. It is found that the nonradiative relaxation of the optical hole is at least 3 orders of magnitude slower in the QDQW than in the QD system. Analysis of the second derivative of the broad transient bleach spectrum of the QDQW system in the 1.6-2.5 eV energy region at 50 fs delay time is found to have a minimum at 2.1 eV, corresponding to a minimum in the radiative probability. Around this energy, the rise and decay times of the transient bleach in the spectrum an found to change greatly. These results suggest that spectral diffusion in the QDQW is a result of relaxation from high- to low-energy exciton states, involving an intervening dark state at an energy of similar to 2.0 eV. The energies of the maxima and minimum of the second-derivative curve are found to be in good agreement with recent theoretical calculations by Jaskolski and Bryant(1) of the energies of the radiative and dark charge-separated state, respectively. In the latter, the hole is in the CdS clad and the electron is in the HgS well. The slow nonradiative relaxation processes involving this state are expected to be slow owing to the large change in the charge carrier effective masses as they cross from the CdS clad to the HgS well.},
	isbn = {1089-5639},
	doi = {10.1021/jp9822687},
	author = {Little, Reginald and Burda, Clemens and Link, Stephan and Logunov, Stephan L. and El-Sayed, Mostafa A}
}
@article {1292,
	title = {Femtosecond Interfacial Electron Transfer Dynamics of CdSe Semiconductor Nanoparticles },
	journal = {MRS Proceedings},
	volume = {43},
	year = {1998},
	pages = {419-424},
	abstract = {The effect of the adsorption of an electron donor (thiophenol, TP) on the surface of CdSe nanoparticles (NPs) on the emission and electron-hole dynamics is studied. It is found that while the emission is completely quenched, the effect on the transient bleach recovery of the band gap absorption is only slight. This is explained by a mechanism in which the hole in the valence band of the NP is rapidly neutralized by electron transfer from the TP. However, the excited electron in the conduction band is not transferred to the TP cation, i. e. the electron does not shuttle via the organic moiety as it does when naphthoquinone is adsorbed [1]. The excited electron is rather trapped by surface states. Thus the rate of bleach recovery in the CdSe NP system is determined by the rate of electron trapping and not by hole trapping. Comparable conclusions resulted previously [2] for the CdS NP when the CdS-MV2+ system is studied. A comparative discussion of the electron-hole dynamics in these systems (CdSe-NQ, CdS-MV2+ and CdSe-TP) is given.},
	doi = {10.1557/PROC-536-419 },
	author = {Burda, Clemens and Green, T.C. and Link, Stephan and El-Sayed, Mostafa A}
}
@article {1256,
	title = {Interfacial carriers dynamics of CdS nanoparticles},
	journal = {Journal of Physical Chemistry A},
	volume = {102},
	number = {28},
	year = {1998},
	note = {Logunov, S Green, T Marguet, S El-Sayed, MA},
	month = {Jul},
	pages = {5652-5658},
	abstract = {The relaxation dynamics of charge carriers in 4 nm CdS colloidal quantum dots are studied by means of picosecond time-resolved fluorescence and femtosecond transient absorption experiments. We also studied the effects of the adsorption of viologen derivatives as electron accepters on the surface of these particles. From these experimental measurements, we reached a model of the electron-hole dynamics in these nanoparticles consistent with previous proposals. In particular, we have confirmed that the electron trapping in these particles is slower than the hole trapping (30 ps versus a few picoseconds). After excitation, rapid formation of an optical hole (bleach) within the lowest energy exciton (band gap) absorption region appears. The maximum of the bleaching band is red-shifted by 20 meV in 2.5 ps, and the bleach intensity recovers in 30 ps. Upon the adsorption of electron accepters, the rate of the red shift of the optical hole is not affected while the bleach recovery time is reduced to a few picoseconds. This leads to the following conclusions: (1) the shift in the bleach band results from hole trapping dynamics, and (2) the bleach recovery is rate limited by the electron trapping process in the CdS nanoparticles (30 ps) or by the hole trapping process (a few picoseconds) in the presence of the electron accepters. The latter conclusion supports a previous proposal by Klimov et al., that the rate of the recovery in CdS nanoparticles is determined by the electron surface trapping process. The electron transfer to the viologen accepters is found to be very efficient and takes place in 200-300 fs, which efficiently competes with surface trapping and electron-hole recombination processes and thus quenches both the band gap and the deep trap emissions.},
	isbn = {1089-5639},
	doi = {10.1021/jp980387g},
	author = {Logunov, Stephan L. and Green, T.C. and Marguet, S. and El-Sayed, Mostafa A}
}
@article {1252,
	title = {Kinetically controlled growth and shape formation mechanism of platinum nanoparticles},
	journal = {Abstracts of Papers of the American Chemical Society},
	volume = {215},
	year = {1998},
	note = {Petroski, JM Wang, ZL Green, TC El-Sayed, MAPart 2},
	month = {Apr},
	pages = {U176-U176},
	isbn = {0065-7727},
	author = {Petroski, J. M. and Wang, Z.L. and Green, T.C. and El-Sayed, Mostafa A}
}
@article {1254,
	title = {Low-temperature retinal photoisomerization dynamics in bacteriorhodopsin},
	journal = {Journal of Physical Chemistry B},
	volume = {102},
	number = {13},
	year = {1998},
	note = {Logunov, SL Masciangioli, TM Kamalov, VF El-Sayed, MA},
	month = {Mar},
	pages = {2303-2306},
	abstract = {Retinal photoisomerization dynamics are studied at both room temperature and 20 K in wild-type bacteriorhodopsin using femtosecond pulses. We were able to resolve the decay at 20 K into two components with the dominant component having a similar lifetime to that observed at room temperature. This strongly suggests that the retinal lifetime at physiological temperature is barrierless. The minor, low-temperature long-lived component is discussed in terms of previous results obtained for fluorescence and transient absorption with lower time resolution, and the origin of this component is discussed in terms of low-temperature glass heterogeneity.},
	isbn = {1089-5647},
	doi = {10.1021/jp972921a},
	author = {Logunov, Stephan L. and Masciangioli, Tina M. and Kamalov, Valey F. and El-Sayed, Mostafa A}
}
@article {1251,
	title = {Primary step in bacteriorhodopsin photosynthesis: Bond stretch rather than angle twist of its retinal excited-state structure},
	journal = {Journal of the American Chemical Society},
	volume = {120},
	number = {34},
	year = {1998},
	note = {Song, L El-Sayed, MA},
	month = {Sep},
	pages = {8889-8890},
	isbn = {0002-7863},
	doi = {10.1021/ja980390d},
	author = {Song, Li and El-Sayed, Mostafa A}
}
@article {1255,
	title = {Quantitative determination of the protein catalytic efficiency for the retinal excited-state decay in bacteriorhodopsin},
	journal = {Journal of Physical Chemistry B},
	volume = {102},
	number = {41},
	year = {1998},
	note = {Logunov, SL Masciangioli, TM El-Sayed, MA},
	month = {Oct},
	pages = {8109-8112},
	abstract = {It was previously found that by removing the negative charge of Asp85 in bacteriorhodopsin (bR), either by protonating it (as in deionized bR) or by mutation to Asn, the decay time of the retinal excited state increases from 0.5 ps to either 1.5 or 10 ps. The two decay components result from the presence of all-trans and 13-cis,15-syn (13-cis) retinal isomers in the modified retinal protein. To quantitatively determine the protein catalysis for the primary process in native bR, we need to determine which decay component results from the excited state of the all-trans isomer (present in the native bR). It is known that the all-trans isomer absorbs at longer wavelength than the 13-cis isomer in blue bR. In this communication, we report the results of pump-probe experiments using 100 fs laser pulses. Probing is carried out at 490 nm, where the excited state in both isomers absorbs. It is found that the ratio of the amplitudes of the two decay components in blue bR changes with variation of the excitation wavelength. The shorter-lived component is found to increase in amplitude as the excitation wavelength increases, i.e., as we excite more of the all-trans isomer. This leads to the conclusion that the short-lived component (1.5 ps) is for the decay of the all-trans excited state while the long-lived component (10 ps) is for the 13-cis retinal excited-state decay. Thus, the presence of the negative charge of Asp85 in native bR catalyzes the rate of the excited-state decay of the all-trans retinal by 300\% and that of the 13-cis isomer by >2000\%.},
	isbn = {1089-5647},
	doi = {10.1021/jp9813600},
	author = {Logunov, Stephan L. and Masciangioli, Tina M. and El-Sayed, Mostafa A}
}
@article {1249,
	title = {Shape transformation and surface melting of cubic and tetrahedral platinum nanocrystals},
	journal = {Journal of Physical Chemistry B},
	volume = {102},
	number = {32},
	year = {1998},
	note = {Wang, ZL Petroski, JM Green, TC El-Sayed, MA},
	month = {Aug},
	pages = {6145-6151},
	abstract = {We report transmission electron microscopic studies of in-situ temperature-induced shape transformation and melting behavior of polymer-capped cubic and tetrahedral nanocrystals. Our results indicate that the surface-capping polymer is removed by annealing the specimen at temperatures between 180 and 250 degrees C. The particle shapes show no change up to similar to 350 degrees C. In the temperature range between 350 and 450 degrees C, a small truncation occurs in the particle shapes but no major shape transformation is observed. The particle shapes experience a dramatic transformation into spherical-like shapes when the temperature is raised above similar to 500 degrees C, where surface diffusion or surface premelting (softening) takes place. Above 600 degrees C, surface melting becomes obvious leading to coalescence of the surfaces of neighboring nanocrystals and a decrease in the volume occupied by the assembled nanocrystals. The surface melting forms a liquid layer a few atomic layers deep around the still solid core of the nanocrystal. This temperature is much lower than the melting point of bulk metallic platinum (1769 degrees C). The reduction in the melting temperature is discussed in terms of the surface tension of the solid-liquid interface (gamma(SL)). For an 8 nm diameter Pt nanocrystal, gamma(SL) is calculated to be 2.0 N m(-1) at 650 degrees C, which is smaller than that of the bulk solid-vapor metal surface tension (gamma(sv)). This reduction is proposed to be due to the compensation of the increase in gamma(sv) of the nanocrystal by the wetting effect at the solid-liquid interface.},
	isbn = {1089-5647},
	doi = {10.1021/jp981594j},
	author = {Wang, Z.L. and Petroski, J. M. and Green, T.C. and El-Sayed, Mostafa A}
}
@article {1253,
	title = {Thermal reshaping of gold nanorods in micelles},
	journal = {Journal of Physical Chemistry B},
	volume = {102},
	number = {47},
	year = {1998},
	note = {Mohamed, MB Ismail, KZ Link, S El-Sayed, MA},
	month = {Nov},
	pages = {9370-9374},
	abstract = {Gold nanorods are prepared in aqueous solution by an electrochemical method and are shape controlled by using capping micelles as described by Yu et al. (J. Phys. Chem. B 1997, 101 (34), 6661). Transmission electron microscopic (TEM) images are determined for these gold nanorods, taken from solutions heated to various temperatures in the range of 25-160 degrees C. Size and shape analysis of their TEM images showed that the mean aspect ratio of the nanorods in solution decreases with increasing temperature, mostly as a result of reduction in their length. Heating the dried nanorods themselves on a TEM slide to much higher temperatures does not produce any shape changes. This suggests that the observed relative instability of the longer nanorods in the micellar solutions is attributed to the relative instability of the micelles capping the longer gold nanorods. Following the change with time of the longitudinal surface plasmon absorption band of the gold nanorods at five different temperatures, the activation energy for the thermal decomposition of the micelles is found to be 21.0 +/- 1.0 K cal mol(-1). The most stable rod-shaped micelle is found to have an aspect ratio of 2.0. The craft decomposition (dissolution) temperature of these micelles is found to be similar to 155 degrees C. This study offers a new method in which the thermal stability of micelles of various shapes is used to change the size distribution of metal nanorods in solution. On the other hand, TEM or the absorption maximum of the longitudinal plasmon resonance of gold nanorods can be used as a sensitive monitor in studying the physical properties of the host micelles themselves.},
	isbn = {1089-5647},
	doi = {10.1021/jp9831482},
	author = {Mohamed, MB and Ismail, K. Z. and Link, Stephan and El-Sayed, Mostafa A}
}
@article {1259,
	title = {A Comparison of the Photoelectric Current Responses Resulting from the Proton Pumping Process of Bacteriorhodopsin under Pulsed and CW Laser Excitations},
	journal = {The Journal of Physical Chemistry B},
	volume = {101},
	year = {1997},
	note = {doi: 10.1021/jp972475r},
	month = {1997},
	pages = {10599 - 10604},
	publisher = {American Chemical Society},
	abstract = {When excited with a pulsed laser, an electric field-oriented bacteriorhodopsin (bR) film on an indium-tin oxide (ITO) conductive electrode generates a photocurrent composed of at least three different components:  B1 (<100 ps), B2 (60 μs), and B3 (ms). When excited with an electronic shutter modulated CW light pulse (>200 ms in duration), a differential photocurrent (components D1 and D2 with decay times in milliseconds) is observed from the bR film. D1 is observed when the CW light is turned on, and D2 is observed when the CW light is turned off. In this paper, we compare the amplitudes and lifetimes of B2, B3, and D1 at various values of pH and ionic strength of the electrolyte solution in which the photocurrent is measured. It is found that changing the film orientation changes the polarity (sign) of B1 and B2, while it does not affect the polarity of B3 and D1. It is also found that B3 and D1 change their polarity upon changing the pH of electrolyte solution, whereas B1 and B2 do not. These results suggest that the origin of B3 and D1 is different from that of B1 and B2. Our results suggest that B3 and D1 are due to the formation of a transient proton capacitor between the two ITO electrodes resulting from the proton pumping in bR. The magnitude and sign of B3 and D1 are determined by the transient proton concentration change (accumulation or disappearance) occurring near the bR-modified ITO electrode interface on the millisecond time scale. The change of sign in B3 and D1 as a function of pH is due to the sequence of proton release/uptake in the bR photocycle:  It first releases protons into the aqueous solution at high pH, while it first takes up protons from the aqueous solution at low pH. The effects of buffer and ionic strength on B3 and D1 are discussed in terms of the kinetics of proton release/uptake and of the transportation of positive and negative ions in the electrolyte solution.},
	isbn = {1520-6106},
	url = {http://dx.doi.org/10.1021/jp972475r},
	author = {Wang, Jianping and Song, Li and Yoo, Seoung-Kyo and El-Sayed, Mostafa A}
}
@article {1263,
	title = {Effect of Lattice Energy Mismatch on the Relative Mass Peak Intensities of Mixed Alkali Halide Nanocrystals},
	journal = {The Journal of Physical Chemistry A},
	volume = {101},
	year = {1997},
	note = {doi: 10.1021/jp962045l},
	month = {1997},
	pages = {690 - 693},
	publisher = {American Chemical Society},
	abstract = {The relative mass peak intensity distribution of the [M14-nAnI13]+ mixed alkali halide nanocrystals containing a ?magic? number of 14 metal cations (M and A) and 13 iodide anions is examined. These nanocrystals were generated through sputtering of mixed solid alkali halides using fast atom bombardment and analyzed by use of a double-focusing sector field mass spectrometer. The mass peak intensities of mixed cluster ions composed of two different metals relative to the ?pure? nanocrystals (containing one or the other metal) are compared for two types of mixed cluster ions:? one with small lattice energy mismatch, i.e., [Rb14-nKnI13]+ cluster ions, and the other type with large lattice energy mismatch, i.e., [Cs14-nAnI13]+ cluster ions where A is either Na, K, or Rb. In contrast to what was previously1 found for clusters with small energy mismatch in which the rate of formation (which depends on the possible number of isomers that each mixed cluster ion can have) determines the relative intensities of mass peaks, the rate of evaporation (i.e., the cluster instability) determines the relative mass peak intensities in salts with relatively large lattice energy mismatch. These results are consistent with our previously proposed kinetic model for the formation and decay of these clusters.The relative mass peak intensity distribution of the [M14-nAnI13]+ mixed alkali halide nanocrystals containing a ?magic? number of 14 metal cations (M and A) and 13 iodide anions is examined. These nanocrystals were generated through sputtering of mixed solid alkali halides using fast atom bombardment and analyzed by use of a double-focusing sector field mass spectrometer. The mass peak intensities of mixed cluster ions composed of two different metals relative to the ?pure? nanocrystals (containing one or the other metal) are compared for two types of mixed cluster ions:? one with small lattice energy mismatch, i.e., [Rb14-nKnI13]+ cluster ions, and the other type with large lattice energy mismatch, i.e., [Cs14-nAnI13]+ cluster ions where A is either Na, K, or Rb. In contrast to what was previously1 found for clusters with small energy mismatch in which the rate of formation (which depends on the possible number of isomers that each mixed cluster ion can have) determines the relative intensities of mass peaks, the rate of evaporation (i.e., the cluster instability) determines the relative mass peak intensities in salts with relatively large lattice energy mismatch. These results are consistent with our previously proposed kinetic model for the formation and decay of these clusters.},
	isbn = {1089-5639},
	doi = {doi: 10.1021/jp962045l},
	url = {http://dx.doi.org/10.1021/jp962045l},
	author = {Ahmadi, Temer S. and El-Sayed, Mostafa A}
}
@article {868,
	title = {Electron Dynamics of Passivated Gold Nanocrystals Probed by Subpicosecond Transient Absorption Spectroscopy},
	journal = {The Journal of Physical Chemistry B},
	volume = {101},
	year = {1997},
	note = {doi: 10.1021/jp962923f},
	month = {1997},
	pages = {3713 - 3719},
	publisher = {American Chemical Society},
	abstract = {The electronic dynamics of gold nanocrystals, passivated by a monolayer of alkylthiol(ate) groups, were studied by transient spectroscopy after excitation with subpicosecond laser pulses. Three solution-phase gold samples with average particle size of 1.9, 2.6, and 3.2 nm with size distribution less than 10\% were used. The photoexcitation in the intraband (surface plasmon region) leads to the heating of the conduction electron gas and its subsequent thermalization through electron?electron and electron?phonon interaction. The results are analyzed in terms of the contribution of the equilibrated ?hot? electrons to the surface plasmon resonance of gold. A different spectral response was observed for different sizes of gold nanoparticles. The results were compared to the dynamics of the large (30 nm diameter) gold nanocrystals colloidal solution. The size-dependent spectral changes are attributed to the reduction of the density of states for small nanoparticles. The observed variation in the kinetics of the cooling process in gold nanoparticles with changing the laser intensity is attributed to the temperature dependence of the heat capacity of the electron gas.The electronic dynamics of gold nanocrystals, passivated by a monolayer of alkylthiol(ate) groups, were studied by transient spectroscopy after excitation with subpicosecond laser pulses. Three solution-phase gold samples with average particle size of 1.9, 2.6, and 3.2 nm with size distribution less than 10\% were used. The photoexcitation in the intraband (surface plasmon region) leads to the heating of the conduction electron gas and its subsequent thermalization through electron?electron and electron?phonon interaction. The results are analyzed in terms of the contribution of the equilibrated ?hot? electrons to the surface plasmon resonance of gold. A different spectral response was observed for different sizes of gold nanoparticles. The results were compared to the dynamics of the large (30 nm diameter) gold nanocrystals colloidal solution. The size-dependent spectral changes are attributed to the reduction of the density of states for small nanoparticles. The observed variation in the kinetics of the cooling process in gold nanoparticles with changing the laser intensity is attributed to the temperature dependence of the heat capacity of the electron gas.},
	isbn = {1520-6106},
	url = {http://dx.doi.org/10.1021/jp962923f},
	author = {Logunov, Stephan L. and Ahmadi, Temer S. and El-Sayed, Mostafa A and Khoury, J. T. and Whetten, R. L.}
}
@article {1262,
	title = {Laser Multiphoton Dissociation Ionization of Acrolein Clusters},
	journal = {The Journal of Physical Chemistry A},
	volume = {101},
	year = {1997},
	note = {doi: 10.1021/jp9605010},
	month = {1997},
	pages = {3699 - 3701},
	publisher = {American Chemical Society},
	abstract = {Clusters of acrolein, C3H4O, are formed by supersonic expansion techniques. The acrolein clusters are ionized and decomposed by 193 nm light from an excimer laser and detected by time-of-flight mass spectrometry. The dominant channel of decomposition involves the loss of a carbon atom from all the clusters. The loss of C2, C3, and even up to C6 is also observed from larger clusters. The presence of clusters with more hydrogen atoms than expected for multiples of acrolein molecules suggests that reactions within the cluster and evaporation are important processes. The mechanisms of the dissociation routes are discussed in terms of ladder and ladder-switching processes within individual molecules within the cluster.Clusters of acrolein, C3H4O, are formed by supersonic expansion techniques. The acrolein clusters are ionized and decomposed by 193 nm light from an excimer laser and detected by time-of-flight mass spectrometry. The dominant channel of decomposition involves the loss of a carbon atom from all the clusters. The loss of C2, C3, and even up to C6 is also observed from larger clusters. The presence of clusters with more hydrogen atoms than expected for multiples of acrolein molecules suggests that reactions within the cluster and evaporation are important processes. The mechanisms of the dissociation routes are discussed in terms of ladder and ladder-switching processes within individual molecules within the cluster.},
	isbn = {1089-5639},
	doi = {doi: 10.1021/jp9605010},
	url = {http://dx.doi.org/10.1021/jp9605010},
	author = {Morita, Hiroshi and Freitas, John E. and El-Sayed, Mostafa A}
}
@article {874,
	title = {Molecular Mechanism of the Differential Photoelectric Response of Bacteriorhodopsin},
	journal = {The Journal of Physical Chemistry B },
	volume = {101},
	year = {1997},
	note = {doi: 10.1021/jp962111j},
	month = {1997},
	pages = {3420 - 3423},
	publisher = {American Chemical Society},
	abstract = {In order to determine the molecular origin of the differential photocurrent from bacteriorhodopsin (bR), the photoelectric response of bR film deposited on an indium tin oxide (ITO) conductive glass electrode under CW excitation is compared with that under pulsed laser excitation at different pH and with opposite membrane orientation with respect to the ITO electrode surface. The characteristics (sign and magnitude) of the dominant component of the differential photocurrent (appearing on the millisecond time scale) are found to correlate with the process of proton release into, or uptake from, the aqueous solution during the photocycle under different experimental conditions. This suggests that the differential current results mainly from the change in the H+ concentration at the bR?ITO electrode interface.In order to determine the molecular origin of the differential photocurrent from bacteriorhodopsin (bR), the photoelectric response of bR film deposited on an indium tin oxide (ITO) conductive glass electrode under CW excitation is compared with that under pulsed laser excitation at different pH and with opposite membrane orientation with respect to the ITO electrode surface. The characteristics (sign and magnitude) of the dominant component of the differential photocurrent (appearing on the millisecond time scale) are found to correlate with the process of proton release into, or uptake from, the aqueous solution during the photocycle under different experimental conditions. This suggests that the differential current results mainly from the change in the H+ concentration at the bR?ITO electrode interface.},
	isbn = {1520-6106},
	url = {http://dx.doi.org/10.1021/jp962111j},
	author = {Wang, Jianping and Yoo, Seoung-Kyo and Song, Li and El-Sayed, Mostafa A}
}
@article {1289,
	title = {On the molecular origin of the protein catalysis of the primary process in bacteriorhodopsin photosynthesis: Retinal photoisomerization},
	journal = {Pure and Applied Chemistry},
	volume = {69},
	number = {4},
	year = {1997},
	note = {Times Cited: 816th IUPAC Symposium on PhotochemistryJul 21-26, 1996Helsinki, finlandIupac},
	month = {Apr},
	pages = {749-754},
	abstract = {Using subpicosecond transient optical absorption spectroscopic techniques, the photoisomerization rates and quantum yields were determined for. bacteriorhodopsin, its relevant mutants, its dionized form and at different pH and Cl- concentrations. It is found that the rate is catalyzed and made highly specific around the C-13-C-14 bond by the presence of negative charges within the retinal cavity (e.g., Asp85 and Asp 212). Any perturbation that genetically removes, acid neutralizes, or changes the geometry of these negative charges is found to decrease the tate of photoisomerization, but does not greatly change its quantum yield. These results sue discussed in terms of the changes in the electronic structure of the retinal as well as in the anisotropic charge distribution within the cavity that result from the photoexcitation process. The different potential energy surfaces proposed to explain the dynamics of the photoisomerization process are examined in terms of our observed results.},
	isbn = {0033-4545},
	doi = {10.1351/pac199769040749},
	author = {El-Sayed, Mostafa A and Logunov, Stephan L.}
}
@article {864,
	title = {Optical rotation of the second harmonic radiation from retinal in bacteriorhodopsin monomers in Langmuir-Blodgett film: evidence for nonplanar retinal structure.},
	journal = {Biophysical journal},
	volume = {73},
	year = {1997},
	month = {1997 Dec},
	pages = {3164-70},
	abstract = {We observed optical rotation of the plane of polarization of the second harmonic (SH) radiation at 532 nm (in resonance with the retinal absorption) generated in reflection geometry in Langmuir-Blodgett film of bacteriorhodopsin (bR). The analysis of the experimental data showed that this effect arises from the nonvanishing contribution of the antisymmetrical part of the hyperpolarizability tensor. This requires that the dipole moment of the resonant electronic transition, the change of the dipole moment upon electronic excitation, and the long axis of the retinal not be coplanar. Such conditions are satisfied only if the retinal has a nonplanar geometry, a conclusion that could lend support to the heterogeneity model of the origin of the biphasic band shape of the linear CD spectrum of the retinal in bR. On the basis of our theoretical analysis, we were able to estimate the angle between the induced dipole moment and the plan that contains the long axis of the chromophore and the transition dipole moment of the retinal absorption.},
	keywords = {Bacteriorhodopsins, Biophysical Phenomena, Biophysics, Circular Dichroism, Molecular Structure, Optics and Photonics, Retinaldehyde, Spectrophotometry},
	issn = {0006-3495},
	doi = {10.1016/S0006-3495(97)78342-5},
	author = {Volkov, V. V. and Svirko, Y P and Kamalov, Valey F. and Song, Li and El-Sayed, Mostafa A}
}
@article {1258,
	title = {Photofragment translational spectroscopy of CH2I2 at 304 nm: Polarization dependence and energy partitioning},
	journal = {Bulletin of the Korean Chemical Society},
	volume = {18},
	number = {12},
	year = {1997},
	note = {Jung, KW Ahmadi, TS El-Sayed, MA},
	month = {Dec},
	pages = {1274-1280},
	abstract = {The photodissociation dynamics of CH2I2 has been studied at 304 nm by state-selective photofragment translational spectroscopy. Velocity distributions, anisotropy parameters, and relative quantum yields are obtained for the ground I(P-2(3/2)) and spin-orbit excited state I*(P-2(1/2)) iodine atoms, which are produced from photodissociation of CH2I2 at this wavelength. These processes are found to occur via B-1 <-- A(1) type electronic transitions. The quantum yield of I*(P-2(1/2)) is determined to be 0.25, indicating that the formation of ground state iodine is clearly the favored dissociation channel in the 304 nm wavelength region. From the angular distribution of dissociation products, the anisotropy parameters are determined to be beta(I)=0.4 for the I(P-2(3/2)) and beta (I*)=0.55 for the I*(P-2(1/2)) which substantially differ from the limiting value of 1.13. The positive values of anisotropy parameter, however, show that the primary processes for I and I* formation channels proceed dominantly via a transition which is parallel to I-I axis. The above results are interpreted in terms of dual path formation of iodine atoms from two different excited states, i.e., a direct and an indirect dissociation via curve crossing between these states. The translational energy distributions of recoil fragments reveal that a large fraction of the available energy goes into the internal excitation of the CH2I photofragment; <E-int>/E-avl=0.80 and 0.82 for the I and I* formation channels, respectively. The quantitative analysis for the energy partitioning of available energy into the photofragments is used to compare the experimental results with the prediction of direct impulsive model for photodissociation dynamics.},
	isbn = {0253-2964},
	author = {Jung, Kwang-Woo and Ahmadi, Temer S. and El-Sayed, Mostafa A}
}
@article {1290,
	title = {Photofragment Translational Spectroscopy of ICl at 304 nm},
	journal = {The Journal of Physical Chemistry A},
	volume = {101},
	year = {1997},
	note = {doi: 10.1021/jp970837p},
	month = {1997},
	pages = {6562 - 6567},
	publisher = {American Chemical Society},
	abstract = {The photodissociation dynamics of ICl is studied at 304 nm by state-selective photofragment translational spectroscopy. Velocity distributions, anisotropy parameters, and relative quantum yields are obtained for the ground I(2P3/2) and spin?orbit excited state I*(2P1/2) iodine atoms, which are produced from photodissociation of ICl at this wavelength. Two sharp velocity distributions are observed for the I channel, suggesting the existence of two dissociation pathways that correlate with ground state iodine formation. Based on the expected translational energy release and the energy separation between those peaks, the two distributions are assigned to dissociation of ICl to I(2P3/2) + Cl(2P3/2) and to I(2P3/2) + Cl*(2P1/2); the former channel appears at higher translational energy. The distribution of I* also shows two strong peaks, indicating that there are two dominant channels for the formation of I* atoms at this wavelength which we assign to the dissociation of ICl forming I*(2P1/2) + Cl(2P3/2) and I*(2P1/2) + Cl*(2P1/2), respectively. The quantum yield of I*(2P1/2) is determined to be 0.30, indicating that the formation of ground state iodine is clearly the favored dissociation channel at 304 nm. The observed anisotropy in the angular distribution of dissociation products (?) indicates that the I* + Cl and I* + Cl* channels are formed predominantly from the parallel transition (? = 1.7 for both channels) while the I + Cl and I + Cl* products are formed mainly from perpendicular transitions (? = ?0.5). The decrease in the anisotropy parameter of the I formation channels from their limiting value of ?1 is attributed to the presence of more than one path for the formation of I + Cl/Cl* photoproducts with opposite polarization for their absorbing transitions. The possible excited state dynamics, which give the observed results, are discussed in terms of the previously proposed energy correlation diagram for ICl.The photodissociation dynamics of ICl is studied at 304 nm by state-selective photofragment translational spectroscopy. Velocity distributions, anisotropy parameters, and relative quantum yields are obtained for the ground I(2P3/2) and spin?orbit excited state I*(2P1/2) iodine atoms, which are produced from photodissociation of ICl at this wavelength. Two sharp velocity distributions are observed for the I channel, suggesting the existence of two dissociation pathways that correlate with ground state iodine formation. Based on the expected translational energy release and the energy separation between those peaks, the two distributions are assigned to dissociation of ICl to I(2P3/2) + Cl(2P3/2) and to I(2P3/2) + Cl*(2P1/2); the former channel appears at higher translational energy. The distribution of I* also shows two strong peaks, indicating that there are two dominant channels for the formation of I* atoms at this wavelength which we assign to the dissociation of ICl forming I*(2P1/2) + Cl(2P3/2) and I*(2P1/2) + Cl*(2P1/2), respectively. The quantum yield of I*(2P1/2) is determined to be 0.30, indicating that the formation of ground state iodine is clearly the favored dissociation channel at 304 nm. The observed anisotropy in the angular distribution of dissociation products (?) indicates that the I* + Cl and I* + Cl* channels are formed predominantly from the parallel transition (? = 1.7 for both channels) while the I + Cl and I + Cl* products are formed mainly from perpendicular transitions (? = ?0.5). The decrease in the anisotropy parameter of the I formation channels from their limiting value of ?1 is attributed to the presence of more than one path for the formation of I + Cl/Cl* photoproducts with opposite polarization for their absorbing transitions. The possible excited state dynamics, which give the observed results, are discussed in terms of the previously proposed energy correlation diagram for ICl.},
	isbn = {1089-5639},
	doi = {doi: 10.1021/jp970837p},
	url = {http://dx.doi.org/10.1021/jp970837p},
	author = {Jung, Kwang-Woo and Ahmadi, Temer S. and El-Sayed, Mostafa A}
}
@article {1260,
	title = {Redetermination of the Quantum Yield of Photoisomerization and Energy Content in the K-Intermediate of Bacteriorhodopsin Photocycle and Its Mutants by the Photoacoustic Technique},
	journal = {The Journal of Physical Chemistry B},
	volume = {101},
	year = {1997},
	note = {doi: 10.1021/jp970955c},
	month = {1997},
	pages = {6629 - 6633},
	publisher = {American Chemical Society},
	abstract = {Data obtained previously in our lab for the quantum yield retinal photoisomerization and the energy content of the K-intermediate formed in the bacteriorhodopsin and its mutants (bR) photocycle are reexamined using time-resolved transient spectroscopy and laser-induced photoacoustic spectroscopy. In the present experiment both nanosecond and subpicosecond laser pulses are used for excitation, with different reference compounds. From these new results it can be concluded that using CoCl2 as a reference compound in the photoacoustic experiment with subpicosecond laser pulses gives a large amount of prompt heat release resulting from multiphoton absorption processes. This results in an overestimated energy content of the K-intermediate of bR and its mutants. Using different reference compounds, the corrected values are 40 {\textpm} 10 kJ/mol, which is in agreement with previously reported values. The apparent quantum yield and energy content values (for each of the isomeric compositions) of the mutants D212N, D85N, R82Q, A53G, W182F, V49A, deionized blue bR, and acid purple bR are also recalculated using bR as a reference compound and are similar to those of bR. (Φ is in the range 0.55?0.65, and EK is in the range 40?50 kJ/mol.) The relative insensitivity of the apparent average quantum yield value is discussed.Data obtained previously in our lab for the quantum yield retinal photoisomerization and the energy content of the K-intermediate formed in the bacteriorhodopsin and its mutants (bR) photocycle are reexamined using time-resolved transient spectroscopy and laser-induced photoacoustic spectroscopy. In the present experiment both nanosecond and subpicosecond laser pulses are used for excitation, with different reference compounds. From these new results it can be concluded that using CoCl2 as a reference compound in the photoacoustic experiment with subpicosecond laser pulses gives a large amount of prompt heat release resulting from multiphoton absorption processes. This results in an overestimated energy content of the K-intermediate of bR and its mutants. Using different reference compounds, the corrected values are 40 {\textpm} 10 kJ/mol, which is in agreement with previously reported values. The apparent quantum yield and energy content values (for each of the isomeric compositions) of the mutants D212N, D85N, R82Q, A53G, W182F, V49A, deionized blue bR, and acid purple bR are also recalculated using bR as a reference compound and are similar to those of bR. (Φ is in the range 0.55?0.65, and EK is in the range 40?50 kJ/mol.) The relative insensitivity of the apparent average quantum yield value is discussed.},
	isbn = {1520-6106},
	url = {http://dx.doi.org/10.1021/jp970955c},
	author = {Logunov, Stephan L. and El-Sayed, Mostafa A}
}
@article {1261,
	title = {Spectral diffusion within the porous silicon emission wavelength range on the nanosecond to millisecond time scale},
	journal = {J. Appl. Phys.Journal of Applied Physics},
	volume = {82},
	year = {1997},
	month = {1997},
	pages = {836},
	publisher = {AIP},
	abstract = {The emission spectrum from porous silicon (PS) at room temperature was recorded after different delay times ranging from 30 ns to 2.0 ms after pulsed laser excitation by using a gated charge-coupled device camera. In agreement with previous studies, the photoluminescence of porous silicon was found to redshift with delay time in the ns to 100 μs time scale. However, a study of the normalized band shape of the redshifted emission reveals that the emission spectrum retains its band shape rather than giving a distorted band shape that increases in intensity on the longer wavelength side. This behavior suggests that the redshift in the emission spectrum of porous silicon is a result of spectral diffusion resulting from energy transfer among emitters within the inhomogeneously broadened absorption spectrum. Furthermore, on the longer time scale (0.8{\textendash}2 ms), the much weaker, long wavelength emission spectrum is found to blueshift as the delay time is increased. Two peaks were resolved in the photoluminescence spectrum. One is centered around 650 nm and the other is centered around 750 nm. The photoluminescence at 600 and 800 nm have lifetimes of 0.35 and 0.19 ms, respectively. This observation suggests the existence of two distinct molecular species responsible for the observed photoluminescence in PS.},
	keywords = {elemental semiconductors, photoluminescence, porous materials, radiative lifetimes, red shift, silicon, spectral line breadth, spectral line shift, time resolved spectra},
	url = {http://dx.doi.org/10.1063/1.365781},
	author = {Song, Li},
	editor = {El-Sayed, Mostafa A and Chen, P.}
}
@article {871,
	title = {Steps, ledges and kinks on the surfaces of platinum nanoparticles of different shapes},
	journal = {Surface science},
	volume = {380},
	year = {1997},
	pages = {302-310},
	publisher = {Elsevier},
	abstract = {Platinum nanoparticles with a high percentage of cubic-, tetrahedral- and octahedral-like shapes, respectively, have been synthesized by a shape-controlling technique that we developed recently [Ahmadi et al., Science 272 (June 1996) 1924]. High resolution transmission electron microscopy (HRTEM) is used here to directly image the atomic scale structures of the surfaces of these particles with different shapes. The truncated shapes of these particles are mainly defined by the {100}, {111}, and {110} facets, on which numerous atom-high surface steps, ledges and kinds have been observed. This atomic-scale fine structure of the surfaces of these particles is expected to play a critical role in their catalytic activity and selectivity.},
	isbn = {0039-6028},
	doi = {10.1016/S0039-6028(97)05180-7 },
	author = {Wang, Z.L. and Ahmad, TS and El-Sayed, Mostafa A}
}
@article {865,
	title = {Studies of cation binding in ZnCl2-regenerated bacteriorhodopsin by x-ray absorption fine structures: effects of removing water molecules and adding Cl- ions.},
	journal = {Biophysical journal},
	volume = {73},
	year = {1997},
	month = {1997 Oct},
	pages = {2097-105},
	abstract = {The binding of Zn2+ in Zn2+-regenerated bacteriorhodopsin (bR) was studied under various conditions by x-ray absorption fine structures (XAFS). The 0.9:1 and 2:1 Zn2+:bR samples gave similar XAFS spectra, suggesting that Zn2+ might have only one strong binding site in bR. It was found that in aqueous bR solution, Zn2+ has an average of six oxygen or nitrogen ligands. Upon drying, two ligands are lost, suggesting the existence of two weakly bound water ligands near the cation-binding site in bacteriorhodopsin. When excess Cl- ions were present before drying in the Zn2+-regenerated bR samples, it was found that two of the ligands were replaced by Cl- ions in the dried film, whereas two remain unchanged. The above observations suggest that Zn2+ has three types of ligands in regenerated bR (referred to as types I, II, and III). Type I ligands are strongly bound. These ligands cannot be removed by drying or by exchanging with Cl- ions. Type II ligands cannot be removed by drying, but can be replaced by Cl- ligands. Type III ligands are weakly bound to the metal cation and are most likely water molecules that can be removed by evaporation under vacuum or by drying with anhydrous CaSO4. The results are discussed in terms of the possible structure of the strongly binding site of Zn2+ in bR.},
	keywords = {Bacteriorhodopsins, Binding Sites, Biophysical Phenomena, Biophysics, Cations, Chlorides, Kinetics, Ligands, Spectrum Analysis, Water, X-Rays, Zinc, Zinc Compounds},
	issn = {0006-3495},
	doi = {10.1016/S0006-3495(97)78240-7},
	author = {Zhang, K and Song, Li and Dong, J and El-Sayed, Mostafa A}
}
@article {1270,
	title = {Calcium and Magnesium Binding in Native and Structurally Perturbed Purple Membrane},
	journal = {The Journal of Physical Chemistry},
	volume = {100},
	year = {1996},
	note = {doi: 10.1021/jp952951i},
	month = {1996},
	pages = {929 - 933},
	publisher = {American Chemical Society},
	abstract = {The number and identity of the metal cations bound to wild-type bacteriorhodopsin (bR) are determined by using inductively coupled plasma mass spectrometry (ICP-MS) and ICP emission techniques. The results indicate that there at ≈2 total Ca2+ and Mg2+ per bR molecule with a ratio of ≈3:1 Ca2+ to Mg2+. This observed ratio is found to agree with the calculated ratio using previously determined binding constants for the two high affinity sites of Ca2+ to deionized bR (Zhang; et al. Biophys. J. 1992, 61, 1201). This suggests that the high-affinity binding sites in deionized bR are similar to those in native bR. Structural perturbation of the native membrane by cleavage of the C-terminus decreases the number of ions per bR to 1.4. The observed ratio of total ions in this sample to total ions in bR is found to agree with that calculated using known binding constants for each. The results on the number of metal cations/bR and their ratio in bacterio-opsin agrees with the calculated number using previously observed binding constants in deionized bO (Yang; et al. Biophys J., in press) only if one assumes that the second high-affinity site (not the first) is removed by retinal removal. Removal of 75\% of the lipids from the purple membrane is found to greatly reduce the number of metal cations from 2 to 0.16. This suggest that if metal cations are in the two high-affinity sites (which are the only type of binding sites evident in our native bR sample), the removal of lipids, known to change the protein tertiary structure, changes also the metal ion binding sites.The number and identity of the metal cations bound to wild-type bacteriorhodopsin (bR) are determined by using inductively coupled plasma mass spectrometry (ICP-MS) and ICP emission techniques. The results indicate that there at ≈2 total Ca2+ and Mg2+ per bR molecule with a ratio of ≈3:1 Ca2+ to Mg2+. This observed ratio is found to agree with the calculated ratio using previously determined binding constants for the two high affinity sites of Ca2+ to deionized bR (Zhang; et al. Biophys. J. 1992, 61, 1201). This suggests that the high-affinity binding sites in deionized bR are similar to those in native bR. Structural perturbation of the native membrane by cleavage of the C-terminus decreases the number of ions per bR to 1.4. The observed ratio of total ions in this sample to total ions in bR is found to agree with that calculated using known binding constants for each. The results on the number of metal cations/bR and their ratio in bacterio-opsin agrees with the calculated number using previously observed binding constants in deionized bO (Yang; et al. Biophys J., in press) only if one assumes that the second high-affinity site (not the first) is removed by retinal removal. Removal of 75\% of the lipids from the purple membrane is found to greatly reduce the number of metal cations from 2 to 0.16. This suggest that if metal cations are in the two high-affinity sites (which are the only type of binding sites evident in our native bR sample), the removal of lipids, known to change the protein tertiary structure, changes also the metal ion binding sites.},
	isbn = {0022-3654},
	doi = {doi: 10.1021/jp952951i},
	url = {http://dx.doi.org/10.1021/jp952951i},
	author = {Griffiths, Jennifer A. and King, John and Yang, Difei and Browner, Richard and El-Sayed, Mostafa A}
}
@article {863,
	title = {Catalysis of the retinal subpicosecond photoisomerization process in acid purple bacteriorhodopsin and some bacteriorhodopsin mutants by chloride ions.},
	journal = {Biophysical journal},
	volume = {71},
	year = {1996},
	month = {1996 Sep},
	pages = {1545-53},
	abstract = {The dynamics and the spectra of the excited state of the retinal in bacteriorhodopsin (bR) and its K-intermediate at pH 0 was compared with that of bR and halorhodopsin at pH 6.5. The quantum yield of photoisomerization in acid purple bR was estimated to be at least 0.5. The change of pH from 6.5 to 2 causes a shift of the absorption maximum from 568 to 600 nm (acid blue bR) and decreases the rate of photoisomerization. A further decrease in pH from 2 to 0 shifts the absorption maximum back to 575 nm when HCl is used (acid purple bR). We found that the rate of photoisomerization increases when the pH decreases from 2 to 0. The effect of chloride anions on the dynamics of the retinal photoisomerization of acid bR (pH 2 and 0) and some mutants (D85N, D212N, and R82Q) was also studied. The addition of 1 M HCl (to make acid purple bR, pH 0) or 1 M NaCl to acid blue bR (pH 2) was found to catalyze the rate of the retinal photoisomerization process. Similarly, the addition of 1 M NaCl to the solution of some bR mutants that have a reduced rate of retinal photoisomerization (D85N, D212N, and R82Q) was found to catalyze the rate of their retinal photoisomerization process up to the value observed in wild-type bR. These results are explained by proposing that the bound Cl- compensates for the loss of the negative charges of the COO- groups of Asp85 and/or Asp212 either by neutralization at low pH or by residue replacement in D85N and D212N mutants.},
	keywords = {Acoustics, Anions, Bacteriorhodopsins, Biophysical Phenomena, Biophysics, Catalysis, Chlorides, Halobacterium salinarum, Hydrogen-Ion Concentration, Kinetics, Photochemistry, Point Mutation, Retinaldehyde, Spectrophotometry},
	issn = {0006-3495},
	doi = {10.1016/S0006-3495(96)79357-8},
	author = {Logunov, Stephan L. and El-Sayed, Mostafa A and Lanyi, Janos K.}
}
@article {877,
	title = {{\textquotedblleft}Cubic{\textquotedblright} Colloidal Platinum Nanoparticles},
	journal = {Chemistry of Materials},
	volume = {8},
	year = {1996},
	note = {doi: 10.1021/cm9601190},
	month = {1996},
	pages = {1161 - 1163},
	publisher = {American Chemical Society},
	abstract = {Cubic platinum nanoparticles (4-18 nm) have been synthesized for the first time in solution by the controlled reduction of K2PtCl4 with hydrogen gas in the presence of sodium polyacrylate as a capping material. The nanoparticles are found to have fee structures, similar to the bulk metal with {100} facets.},
	isbn = {0897-4756},
	doi = {10.1021/cm9601190},
	url = {http://dx.doi.org/10.1021/cm9601190},
	author = {Ahmadi, Temer S. and Wang, Z.L. and Henglein, A. and El-Sayed, Mostafa A}
}
@article {866,
	title = {Detection of a Yb3+ binding site in regenerated bacteriorhodopsin that is coordinated with the protein and phospholipid head groups.},
	journal = {Proceedings of the National Academy of Sciences of the United States of America},
	volume = {93},
	year = {1996},
	month = {1996 Dec 10},
	pages = {14333-7},
	abstract = {Near infrared Yb3+ vibronic sideband spectroscopy was used to characterize specific lanthanide binding sites in bacteriorhodopsin (bR) and retinal free bacteriorhodopsin (bO). The VSB spectra for deionized bO regenerated with a ratio of 1:1 and 2:1 ion to bO are identical. Application of a two-dimensional anti-correlation technique suggests that only a single Yb3+ site is observed. The Yb3+ binding site in bO is observed to consist of PO2- groups and carboxylic acid groups, both of which are bound in a bidentate manner. An additional contribution most likely arising from a phenolic group is also observed. This implies that the ligands for the observed single binding site are the lipid head groups and amino acid residues. The vibronic sidebands of Yb3+ in deionized bR regenerated at a ratio of 2:1 ion to bR are essentially identical to those in bO. The other high-affinity binding site is thus either not evident or its fluorescence is quenched. A discussion is given on the difference in binding of Ca2+ (or Mg2+) and lanthanides in phospholipid membrane proteins.},
	keywords = {Bacteriorhodopsins, Binding Sites, Metals, Rare Earth, Phospholipids, Retinaldehyde, Spectroscopy, Near-Infrared},
	issn = {0027-8424},
	author = {Roselli, Cecile and Boussac, A and Mattioli, T A and Griffiths, Jennifer A. and El-Sayed, Mostafa A}
}
@article {1266,
	title = {Effect of Binding of Lanthanide Ions on the Bacteriorhodopsin Hexagonal Structure:  An X-ray Study},
	journal = {The Journal of Physical Chemistry},
	volume = {100},
	year = {1996},
	note = {doi: 10.1021/jp960741f},
	month = {1996},
	pages = {12002 - 12007},
	publisher = {American Chemical Society},
	abstract = {The effect of the binding of trivalent lanthanide metal cations (Eu3+, Ho3+, and Dy3+) on the hexagonal structure of bacteriorhodopsin (bR) is investigated at different pH using x-Ray diffraction to examine films made by slow evaporation of the corresponding regenerated bR. It is observed that the lanthanide-regenerated bR (at a ratio of 2:1 metal ion to bR) does not form a 2D structure isomorphous to that of native bR or Ca2+-regenerated samples at low sample pH. The native bR hexagonal structure is recovered by titration of the sample with sodium hydroxide. The pH at which the hexagonal structure is recovered depends on the charge density of the lanthanide ion used for the regeneration. The higher the charge density of the ion, the higher the pH at which an isomorphous lattice is formed. A model is proposed in which at normal or low pH a complex bidentate and monodentate type binding (which disrupts the lattice hexagonal structure) exists between a lanthanide ion, the O- of PO2- groups, and/or the amino acid residues. At high pH, complexation with OH- takes place, which converts this binding to a simple monodentate type complex that leads to the recovery of the lattice structure. An equation is derived for the pH at which this conversion takes place and is found to be proportional to the binding constant of the lanthanide ions to the O- of the PO2- groups or the amino acid residues and inversely proportional to the binding constant of the lanthanide ion to the OH- groups. This predicts an increase of conversion pH with the charge density of the lanthanide ion, as observed.},
	isbn = {0022-3654},
	doi = {doi: 10.1021/jp960741f},
	url = {http://dx.doi.org/10.1021/jp960741f},
	author = {Griffiths, Jennifer A. and El-Sayed, Mostafa A and Capel, Malcom}
}
@article {1267,
	title = {Effect of Changing the Position and Orientation of Asp85 Relative to the Protonated Schiff Base within the Retinal Cavity on the Rate of Photoisomerization in Bacteriorhodopsin},
	journal = {The Journal of Physical Chemistry},
	volume = {100},
	year = {1996},
	note = {doi: 10.1021/jp960734r},
	month = {1996},
	pages = {10479 - 10481},
	publisher = {American Chemical Society},
	abstract = {Replacement of either Val49 with Ala or Ala53 with Val by site-specific mutagenesis is known to change the position and orientation of the protonated Schiff base relative to Asp85 within the retinal cavity of bacteriorhodopsin (bR) (Brown, L. S.; Gat, Y.; Sheves, M.; Yamazaki, Y.; Maeda, A.; Needleman, R.; Lanyi, J. K. Biochemistry 1994, 33, 12001). The effect of mutation on the rate of the subpicosecond photoisomerization of retinal in bR is examined by using a pump?probe technique. A decrease in the rate of photoisomerization of retinal in V49A and A53V is observed. This is discussed in terms of the previously proposed mechanism of the protein catalysis to the retinal photoisomerization process in bR.Replacement of either Val49 with Ala or Ala53 with Val by site-specific mutagenesis is known to change the position and orientation of the protonated Schiff base relative to Asp85 within the retinal cavity of bacteriorhodopsin (bR) (Brown, L. S.; Gat, Y.; Sheves, M.; Yamazaki, Y.; Maeda, A.; Needleman, R.; Lanyi, J. K. Biochemistry 1994, 33, 12001). The effect of mutation on the rate of the subpicosecond photoisomerization of retinal in bR is examined by using a pump?probe technique. A decrease in the rate of photoisomerization of retinal in V49A and A53V is observed. This is discussed in terms of the previously proposed mechanism of the protein catalysis to the retinal photoisomerization process in bR.},
	isbn = {0022-3654},
	doi = {doi: 10.1021/jp960734r},
	url = {http://dx.doi.org/10.1021/jp960734r},
	author = {Song, Li and El-Sayed, Mostafa A and Lanyi, Janos K.}
}
@article {1265,
	title = {Effects of rapid thermal anneal on refractive index and hydrogen content of plasma-enhanced chemical vapor deposited silicon nitride films},
	journal = {J. Appl. Phys.Journal of Applied Physics},
	volume = {80},
	year = {1996},
	month = {1996},
	pages = {5384},
	publisher = {AIP},
	abstract = {The objective of this paper is to understand and quantify the effects of rapid thermal anneal (RTA) on refractive index, thickness, and hydrogen content of plasma-enhanced, chemical vapor-deposited (PECVD) silicon nitride films. It is shown that RTA is more effective than identical furnace anneal. A threshold in as-deposited refractive index value is found, above which the index of a silicon nitride film increases, while the thickness and bonded hydrogen content decreases as result of the RTA. In addition, the magnitude of increase in the index is proportional to the as-deposited index value. The threshold index value increases with the increase in silicon nitride deposition temperature. A direct correlation is found between the annealing-induced increase in refractive index and the corresponding decrease in total bonded hydrogen concentration in the PECVD silicon nitride films. Finally, it is shown that the release of bonded hydrogen from the film can passivate defects in the underlying silicon substrate and increase the performance of silicon devices such as solar cells. },
	keywords = {ANNEALING, CRYSTAL DEFECTS, CVD, DESORPTION, HYDROGEN, IMPURITIES, REFRACTIVE INDEX, SILICON NITRIDES, THICKNESS, THIN FILMS},
	doi = {10.1063/1.363480},
	url = {http://dx.doi.org/10.1063/1.363480},
	author = {Cai, L.},
	editor = {Rohatgi, A. and Yang, Difei and El-Sayed, Mostafa A}
}
@article {869,
	title = {Excited-State Dynamics of a Protonated Retinal Schiff Base in Solution},
	journal = {The Journal of Physical Chemistry},
	volume = {100},
	year = {1996},
	note = {doi: 10.1021/jp962046d},
	month = {1996},
	pages = {18586 - 18591},
	publisher = {American Chemical Society},
	abstract = {The dynamics of all-trans and 13-cis retinal protonated Schiff base (RPSB) were studied in different solvents by means of picosecond transient spectroscopy. The decay time of the excited state absorption was found to be wavelength dependent due to the contribution of the faster decay of stimulated emission. The stimulated emission has a lifetime of a 2.5-4 ps while the excited state absorption decay is biexponential with lifetimes of 2.5-4 and 10-12 ps. The fluorescence quantum yield is strongly temperature dependent, but viscosity has a small effect on both excited-state lifetime and fluorescence quantum yield. This leads to the conclusion that there is a 600 cm-1 barrier in the excited-state which results from intramolecular electronic factors and not from the solvent viscosity. The comparison of these results with those for the retinal in rhodopsin and bacteriorhodopsin is discussed in terms of the protein catalysis for the retinal photoisomerization.},
	isbn = {0022-3654},
	url = {http://dx.doi.org/10.1021/jp962046d},
	author = {Logunov, Stephan L. and Song, Li and El-Sayed, Mostafa A}
}
@article {875,
	title = {Fluorine Substitution Effects on the Photodissociation Dynamics of Iodobenzene at 304 nm},
	journal = {The Journal of Physical Chemistry },
	volume = {100},
	year = {1996},
	note = {doi: 10.1021/jp952662u},
	month = {1996},
	pages = {7989 - 7996},
	publisher = {American Chemical Society},
	abstract = {The photodissociation dynamics of pentafluoroiodobenzene are investigated by state-selective one-dimensional translation spectroscopy at 304 nm. We have determined the one-dimensional recoil distribution and the spatial distribution in the form of the anisotropy parameter, ?, as well as the photodissociation relative yields of both ground-state I(3P3/2) and excited-state I*(2P1/2) iodine photofragments. The results are compared to those observed for iodobenzene at 304 nm. As in iodobenzene, two velocity distributions were observed for the dissociation channel which gives ground-state iodine:? a sharp, high recoil velocity peak assigned previously to n,σ* excitation and a slow recoil velocity distribution peak assigned previously to π,π* excitation. Unlike in C6H5I, the I* distribution is relatively strong and its spatial anisotropy can be measured. The fluorine perturbation has led to a number of different observations that can be summarized as follows:? (1) The high velocity distribution has a lower average value and much broader width, suggesting more rapid energy redistribution to the fluorinated phenyl ring prior to and during the dissociation process, resulting from stronger coupling between the n,σ* and π,π* states and/or a longer excited-state lifetime; (2) the slow distribution is weaker and has an almost isotropic spatial distribution (the anisotropy parameter ? ≈ 1.0), while in the iodobenzene spectrum ? is correlated with the recoil velocity; (3) the I* quantum yield for C6F5I is 14 times larger than that for iodobenzene; and (4) ? is correlated with the velocity in the I* spectrum found for C6F5I which is not observed for iodobenzene. These observed fluorine perturbations are attributed to an increased mixing between the charge-transfer state (resulting from electron transfer from the iodine nonbonding electrons to the π* orbitals of the fluorinated benzene ring) and both the n,σ* and the ring π,π* states. This leads to two effects:? (1) a decrease in the nonbonding electron density on the iodine, which decreases the spin-orbit interaction between the n,σ* states themselves, resulting in a decrease in the curve-crossing probability (thus increasing the I* yield) and (2) an increase in the coupling between the repulsive n,σ* states and the fluorinated phenyl π,π* states, leading to an increase in the rate of energy redistribution.The photodissociation dynamics of pentafluoroiodobenzene are investigated by state-selective one-dimensional translation spectroscopy at 304 nm. We have determined the one-dimensional recoil distribution and the spatial distribution in the form of the anisotropy parameter, ?, as well as the photodissociation relative yields of both ground-state I(3P3/2) and excited-state I*(2P1/2) iodine photofragments. The results are compared to those observed for iodobenzene at 304 nm. As in iodobenzene, two velocity distributions were observed for the dissociation channel which gives ground-state iodine:? a sharp, high recoil velocity peak assigned previously to n,σ* excitation and a slow recoil velocity distribution peak assigned previously to π,π* excitation. Unlike in C6H5I, the I* distribution is relatively strong and its spatial anisotropy can be measured. The fluorine perturbation has led to a number of different observations that can be summarized as follows:? (1) The high velocity distribution has a lower average value and much broader width, suggesting more rapid energy redistribution to the fluorinated phenyl ring prior to and during the dissociation process, resulting from stronger coupling between the n,σ* and π,π* states and/or a longer excited-state lifetime; (2) the slow distribution is weaker and has an almost isotropic spatial distribution (the anisotropy parameter ? ≈ 1.0), while in the iodobenzene spectrum ? is correlated with the recoil velocity; (3) the I* quantum yield for C6F5I is 14 times larger than that for iodobenzene; and (4) ? is correlated with the velocity in the I* spectrum found for C6F5I which is not observed for iodobenzene. These observed fluorine perturbations are attributed to an increased mixing between the charge-transfer state (resulting from electron transfer from the iodine nonbonding electrons to the π* orbitals of the fluorinated benzene ring) and both the n,σ* and the ring π,π* states. This leads to two effects:? (1) a decrease in the nonbonding electron density on the iodine, which decreases the spin-orbit interaction between the n,σ* states themselves, resulting in a decrease in the curve-crossing probability (thus increasing the I* yield) and (2) an increase in the coupling between the repulsive n,σ* states and the fluorinated phenyl π,π* states, leading to an increase in the rate of energy redistribution.},
	isbn = {0022-3654},
	url = {http://dx.doi.org/10.1021/jp952662u},
	author = {Griffiths, Jennifer A. and Jung, Kwang-Woo and El-Sayed, Mostafa A}
}
@article {1269,
	title = {Homogeneous Line Width of the Different Vibronic Bands of Retinal Absorption in Bacteriorhodopsin by the Hole-Burning Technique},
	journal = {The Journal of Physical Chemistry},
	volume = {100},
	year = {1996},
	note = {doi: 10.1021/jp952971k},
	month = {1996},
	pages = {2762 - 2765},
	publisher = {American Chemical Society},
	abstract = {Using the hole-burning technique, resolved vibrational structure was observed in the retinal absorption spectrum of bacteriorhodopsin (bR) in poly(vinyl alcohol) (PVA) film at 10 K with 556 and 632 nm irradiation. The homogeneous line widths of v = 1 and v = 2 vibronic bands are estimated from the deconvolution of the observed spectrum. The absorption maximum is found to shift by 100?200 cm-1 by using the two excitation wavelengths; resulting from partial site selection due to the contribution of inhomogeneous broadening. The hole width produced by excitation near the zero-phonon band is found to be ?1250 cm-1, which corresponds to a homogeneous width of ?600 cm-1, and the low limit of dephasing time can be estimated as 20 fs. This width is found to be independent of the vibronic band observed.Using the hole-burning technique, resolved vibrational structure was observed in the retinal absorption spectrum of bacteriorhodopsin (bR) in poly(vinyl alcohol) (PVA) film at 10 K with 556 and 632 nm irradiation. The homogeneous line widths of v = 1 and v = 2 vibronic bands are estimated from the deconvolution of the observed spectrum. The absorption maximum is found to shift by 100?200 cm-1 by using the two excitation wavelengths; resulting from partial site selection due to the contribution of inhomogeneous broadening. The hole width produced by excitation near the zero-phonon band is found to be ?1250 cm-1, which corresponds to a homogeneous width of ?600 cm-1, and the low limit of dephasing time can be estimated as 20 fs. This width is found to be independent of the vibronic band observed.},
	isbn = {0022-3654},
	doi = {doi: 10.1021/jp952971k},
	url = {http://dx.doi.org/10.1021/jp952971k},
	author = {Kamalov, Valey F. and Masciangioli, Tina M. and El-Sayed, Mostafa A}
}
@article {1271,
	title = {Monodentate vs Bidentate Binding of Lanthanide Cations to PO2- in Bacteriorhodopsin},
	journal = {The Journal of Physical Chemistry},
	volume = {100},
	year = {1996},
	note = {doi: 10.1021/jp9533279},
	month = {1996},
	pages = {6863 - 6866},
	publisher = {American Chemical Society},
	abstract = {The frequency difference between the symmetric and antisymmetric stretching vibration of PO2- in phosphatidylglycerol phospate (PGP) is used to differentiate between monodentate and bidentate binding of these groups to metal cations in the membrane of bacteriorhodopsin (bR) and phosphatidylglycerol phospate. The binding of Ca2+ to PGP is found to have a frequency difference corresponding to monodentate binding. The symmetric and antisymmetric PO2- bands in bR show similar frequency shifts upon Ca2+ binding, which is independent of pH. This suggests that Ca2+ has a monodentate type binding with the PO2- in bR. In contrast, the PO2- symmetric and antisymmetric frequencies of PGP complexes with trivalent lanthanide cations with higher charge density (Ho3+ and Dy3+) are observed to have smaller separations and to increase their separation with increasing pH toward the value observed for Ca2+ binding. Lanthanide cations (Ho3+, Dy3+, Eu3+, Nd3+, and La3+) binding in bR at pH 4 show small frequency separations that are observed to have similar frequency shifts with pH, the magnitude of which is dependent on the cation. It is proposed that at low pH the lanthanide cations with higher charge density have bidentate binding to bR, while at high pH, complexation with the OH- competes with one of the oxygens of the PO2- for the binding of the lanthanide ion thus changing the bidentate to monodentate type binding.The frequency difference between the symmetric and antisymmetric stretching vibration of PO2- in phosphatidylglycerol phospate (PGP) is used to differentiate between monodentate and bidentate binding of these groups to metal cations in the membrane of bacteriorhodopsin (bR) and phosphatidylglycerol phospate. The binding of Ca2+ to PGP is found to have a frequency difference corresponding to monodentate binding. The symmetric and antisymmetric PO2- bands in bR show similar frequency shifts upon Ca2+ binding, which is independent of pH. This suggests that Ca2+ has a monodentate type binding with the PO2- in bR. In contrast, the PO2- symmetric and antisymmetric frequencies of PGP complexes with trivalent lanthanide cations with higher charge density (Ho3+ and Dy3+) are observed to have smaller separations and to increase their separation with increasing pH toward the value observed for Ca2+ binding. Lanthanide cations (Ho3+, Dy3+, Eu3+, Nd3+, and La3+) binding in bR at pH 4 show small frequency separations that are observed to have similar frequency shifts with pH, the magnitude of which is dependent on the cation. It is proposed that at low pH the lanthanide cations with higher charge density have bidentate binding to bR, while at high pH, complexation with the OH- competes with one of the oxygens of the PO2- for the binding of the lanthanide ion thus changing the bidentate to monodentate type binding.},
	isbn = {0022-3654},
	doi = {doi: 10.1021/jp9533279},
	url = {http://dx.doi.org/10.1021/jp9533279},
	author = {Griffiths, Jennifer A. and Masciangioli, Tina M. and Roselli, Cecile and El-Sayed, Mostafa A}
}
@article {1264,
	title = {Photodissociation dynamics of iodobenzene by state-selective photofragment translational spectroscopy},
	journal = {Journal of Photochemistry and Photobiology A: Chemistry},
	volume = {102},
	year = {1996},
	pages = {13-20},
	publisher = {Elsevier},
	abstract = {State-selective photofragment translational spectroscopy is used to probe the detailed nature of the photodissociation dynamics of iodobenzene at 304 nm. Simultaneous determination of the recoil speed, the spatial anisotropy, and the final state of the iodine fragment reveals that three dissociation channels with different dynamical characteristics compete in the photodissociation of iodobenzene at 304 nm. Based on the observed energy partitioning between the internal and translational modes and the dissociation time td determined from the spatial anisotropy by using a rotational depolarization model, the three dissociation channels are assigned as follows. Two fast dissociation channels, which result in formation of I *(2P1/2) (td=0.4 ps, quantum yield Φ=0.005{\textpm}0.002) and high velocity I(2P3/2) (td=0.3 ps, Φ=0.70{\textpm}0.04), are due to a parallel transition to the repulsive 3Q0(n,σ*) state in the CI bond, followed by dissociation along the same state or curve crossing to the 1Q1 state respectively. A slow dissociation channel (td=0.5{\textendash}1.4 ps, Φ=0.30{\textpm}0.04) which produces low velocity I(2P3/2) is due to a parallel transition to the triplet π,π* state(s) in the phenyl ring that is predissociated by the repulsive n,σ* state(s). The dissociation times determined in the present work are in excellent agreement with those of the recent femtosecond real-time measurements by Cheng et al. at 278 nm},
	isbn = {1010-6030},
	doi = {10.1016/S1010-6030(96)04369-9},
	author = {Hwang, Hyun Jin and El-Sayed, Mostafa A}
}
@article {872,
	title = {Photoisomerization Quantum Yield and Apparent Energy Content of the K Intermediate in the Photocycles of Bacteriorhodopsin, Its Mutants D85N, R82Q, and D212N, and Deionized Blue Bacteriorhodopsin},
	journal = {The Journal of Physical Chemistry},
	volume = {100},
	year = {1996},
	note = {doi: 10.1021/jp9515242},
	month = {1996},
	pages = {2391 - 2398},
	publisher = {American Chemical Society},
	abstract = {The quantum yield of photoisomerization and the energy content of the K intermediate in the photocycle of bacteriorhodopsin and its mutants D85N, R82Q, and D212N and deionized blue bR were measured. Transient optical absorption and photoacoustic spectroscopy with excitation using 400 fs laser pulse were combined to obtain results. The spectroscopic characteristics of the excited state, the J and K intermediates in the photocycle of the mutants, and deionized blue bR were determined. The presence of both 13-cis and all-trans isomers in the ground state of light-adapted D85N, R82Q, and D212N and deionized blue bR makes extraction of the quantum yield for each isomer difficult. Thus, only average values of the quantum yield for these samples were determined. The replacement of charged groups in the vicinity of the retinal Schiff base was found to decrease the rate of the photoisomerization by up to 30 times, but with no signficant change in either the apparent quantum yield of the photoisomerization or the energy stored in the K intermediate. The results are discussed in terms of the different models for the excited and ground state potential surfaces of the retinal configuration in bacteriorhodopsin.The quantum yield of photoisomerization and the energy content of the K intermediate in the photocycle of bacteriorhodopsin and its mutants D85N, R82Q, and D212N and deionized blue bR were measured. Transient optical absorption and photoacoustic spectroscopy with excitation using 400 fs laser pulse were combined to obtain results. The spectroscopic characteristics of the excited state, the J and K intermediates in the photocycle of the mutants, and deionized blue bR were determined. The presence of both 13-cis and all-trans isomers in the ground state of light-adapted D85N, R82Q, and D212N and deionized blue bR makes extraction of the quantum yield for each isomer difficult. Thus, only average values of the quantum yield for these samples were determined. The replacement of charged groups in the vicinity of the retinal Schiff base was found to decrease the rate of the photoisomerization by up to 30 times, but with no signficant change in either the apparent quantum yield of the photoisomerization or the energy stored in the K intermediate. The results are discussed in terms of the different models for the excited and ground state potential surfaces of the retinal configuration in bacteriorhodopsin.},
	isbn = {0022-3654},
	url = {http://dx.doi.org/10.1021/jp9515242},
	author = {Logunov, Stephan L. and El-Sayed, Mostafa A and Song, Li and Lanyi, Janos K.}
}
@article {867,
	title = {Picosecond Dynamics of Colloidal Gold Nanoparticles},
	journal = {The Journal of Physical Chemistry},
	volume = {100},
	year = {1996},
	note = {doi: 10.1021/jp960484e},
	month = {1996},
	pages = {8053 - 8056},
	publisher = {American Chemical Society},
	abstract = {Colloidal gold nanoparticles with an average radius of 15 nm have a surface plasmon absorption band at 530 nm. Excitation by laser pulses of 450 fs duration, and wavelength of 600 or 380 nm ?bleached? the plasmon band and produced a transient absorption at the wings of the ?bleach? spectrum. The transient absorption was found to have a similar temporal behavior at different wavelengths. Analysis of their temporal behavior showed two time constants:? 2.5 ps, and a slower component of >50 ps. Laser excitation close to the plasmon band at 600 nm leads to the formation of ?hot? non-Fermi electronic distribution within the colloidal particles. Transient absorption from these ?hot? electrons led to different absorptions from that of the plasmon absorption of ?cold? electrons. The ?hot? electrons relax via electron?phonon coupling in 2.5 ps, and the phonon?phonon relaxation of the lattice occurs in >50 ps. At 380 nm excitation, the amplitude of the blue wing becomes smaller, and the slow component becomes longer, which could be due to possible excitation of the d-band electrons. These results are discussed in terms of Mie theory and a two-temperature model (TTM), and their consequences on the optical absorption spectrum.Colloidal gold nanoparticles with an average radius of 15 nm have a surface plasmon absorption band at 530 nm. Excitation by laser pulses of 450 fs duration, and wavelength of 600 or 380 nm ?bleached? the plasmon band and produced a transient absorption at the wings of the ?bleach? spectrum. The transient absorption was found to have a similar temporal behavior at different wavelengths. Analysis of their temporal behavior showed two time constants:? 2.5 ps, and a slower component of >50 ps. Laser excitation close to the plasmon band at 600 nm leads to the formation of ?hot? non-Fermi electronic distribution within the colloidal particles. Transient absorption from these ?hot? electrons led to different absorptions from that of the plasmon absorption of ?cold? electrons. The ?hot? electrons relax via electron?phonon coupling in 2.5 ps, and the phonon?phonon relaxation of the lattice occurs in >50 ps. At 380 nm excitation, the amplitude of the blue wing becomes smaller, and the slow component becomes longer, which could be due to possible excitation of the d-band electrons. These results are discussed in terms of Mie theory and a two-temperature model (TTM), and their consequences on the optical absorption spectrum.},
	isbn = {0022-3654},
	url = {http://dx.doi.org/10.1021/jp960484e},
	author = {Ahmadi, Temer S. and Logunov, Stephan L. and El-Sayed, Mostafa A}
}
@article {873,
	title = {Picosecond Electronic Relaxation in CdS/HgS/CdS Quantum Dot Quantum Well Semiconductor Nanoparticles},
	journal = {The Journal of Physical Chemistry },
	volume = {100},
	year = {1996},
	note = {doi: 10.1021/jp953708m},
	month = {1996},
	pages = {6381 - 6384},
	publisher = {American Chemical Society},
	abstract = {Subpicosecond photoexcitation of CdS/HgS/CdS quantum dot quantum well nanoparticles at wavelengths shorter than their interband absorption (390 nm) leads to a photobleach spectrum at longer wavelengths (440?740 nm). The photobleach spectrum changes and its maximum red-shifts with delay time. These results are explained by the rapid quenching of the initially formed laser-excited excitons by two types of energy acceptors (traps); one is proposed to be due to CdS molecules at the CdS/HgS interface, and the other trap is that present in the CdS/HgS/CdS well. The results of the excitation at longer wavelengths as well as the formation and decay of the bleach spectrum at different wavelengths support this description.Subpicosecond photoexcitation of CdS/HgS/CdS quantum dot quantum well nanoparticles at wavelengths shorter than their interband absorption (390 nm) leads to a photobleach spectrum at longer wavelengths (440?740 nm). The photobleach spectrum changes and its maximum red-shifts with delay time. These results are explained by the rapid quenching of the initially formed laser-excited excitons by two types of energy acceptors (traps); one is proposed to be due to CdS molecules at the CdS/HgS interface, and the other trap is that present in the CdS/HgS/CdS well. The results of the excitation at longer wavelengths as well as the formation and decay of the bleach spectrum at different wavelengths support this description.},
	isbn = {0022-3654},
	url = {http://dx.doi.org/10.1021/jp953708m},
	author = {Kamalov, Valey F. and Little, Reginald and Logunov, Stephan L. and El-Sayed, Mostafa A}
}
@article {861,
	title = {Replacement effects of neutral amino acid residues of different molecular volumes in the retinal binding cavity of bacteriorhodopsin on the dynamics of its primary process.},
	journal = {Biophysical journal},
	volume = {70},
	year = {1996},
	month = {1996 Jun},
	pages = {2875-81},
	abstract = {We have determined the rate and quantum yield of retinal photoisomerization, the spectra of the primary transients, and the energy stored in the K intermediate in the photocycle of some bacteriorhodopsin mutants (V49A, A53G, and W182F) in which residue replacements are found to change the Schiff base deprotonation kinetics (and thus the protein-retinal interaction). Because of their change in the local volume resulting from these individual replacements, these substitutions perturb the proton donor-acceptor relative orientation change and thus the Schiff base deprotonation kinetics. These replacements are thus expected to change the charge distribution around the retinal, which controls its photoisomerization dynamics. Subpicosecond transient spectroscopy as well as photoacoustic technique are used to determine the retinal photoisomerization rate, quantum yield, and the energy stored in the K-intermediate for these mutants. The results are compared with those obtained for wild-type bacteriorhodopsin and other mutants in which charged residues in the cavity are replaced by neutral ones. In some of the mutants the rate of photoisomerization is changed, but in none is the quantum yield or the energy stored in the K intermediate altered from that in the wild type. These results are discussed in terms of the shapes of the potential energy surfaces of the excited and ground states of retinal in the perpendicular configuration within the protein and the stabilization of the positive charge in the ground and the excited state of the electronic system of retinal.},
	keywords = {Bacteriorhodopsins, Binding Sites, Biophysical Phenomena, Biophysics, Halobacterium salinarum, Kinetics, Mutagenesis, Site-Directed, Photochemistry, Quantum Theory, Retinaldehyde, Schiff Bases},
	issn = {0006-3495},
	doi = {10.1016/S0006-3495(96)79857-0},
	author = {Logunov, Stephan L. and El-Sayed, Mostafa A and Lanyi, Janos K.}
}
@article {862,
	title = {Shape-Controlled Synthesis of Colloidal Platinum Nanoparticles},
	journal = {Science (New York, N.Y.)},
	volume = {272},
	year = {1996},
	month = {1996 Jun 28},
	pages = {1924-6},
	abstract = {The shapes and sizes of platinum nanoparticles were controlled by changes in the ratio of the concentration of the capping polymer material to the concentration of the platinum cations used in the reductive synthesis of colloidal particles in solution at room temperature. Tetrahedral, cubic, irregular-prismatic, icosahedral, and cubo-octahedral particle shapes were observed, whose distribution was dependent on the concentration ratio of the capping polymer material to the platinum cation. Controlling the shape of platinum nanoparticles is potentially important in the field of catalysis.},
	issn = {1095-9203},
	doi = {10.1126/science.272.5270.1924},
	author = {Ahmadi, Temer S. and Wang, Z.L. and Green, T.C. and Henglein, A. and El-Sayed, Mostafa A}
}
@article {860,
	title = {The Ca2+ binding to deionized monomerized and to retinal removed bacteriorhodopsin.},
	journal = {Biophysical journal},
	volume = {69},
	year = {1995},
	month = {1995 Nov},
	pages = {2056-9},
	abstract = {In our continuing effort to characterize the metal cation binding in bacteriorhodopsin (bR) using Ca(2+)-specific electrodes, potentiometric titration was carried out on deionized solubilized bR (containing monomeric units) and deionized bacterioopsin (bR with its retinal removed). Scatchard plots were analyzed. The monomer was found to have plots similar to those of the trimer, suggesting that the binding sites in bR are localized within the protein monomer unit and not between the molecules within the trimer structure. This also supports the previous assumption that the curvature in the Scatchard plot of regenerated bR is not due to cooperativity of metal cation within the trimer, but rather due to multiple sites. Recent studies further support the finding that the curved Scatchard plot is not due to the cooperativity between the metal ions in the two high affinity sites, wherever they are. The results of the analysis of the Scatchard plot for deionized bacterioopsin have shown a change in the binding characteristics of the high affinity but not the low affinity sites from that observed in bR. This result supports previous conclusions that metal cations in the high affinity sites are not far from the retinal cavity.},
	keywords = {Bacteriorhodopsins, Binding Sites, Biophysical Phenomena, Biophysics, Calcium, Electrochemistry, Halobacterium, Ions, Kinetics, Protein Conformation, Retinaldehyde},
	issn = {0006-3495},
	doi = {10.1016/S0006-3495(95)80075-5},
	author = {Yang, Difei and El-Sayed, Mostafa A}
}
@article {1275,
	title = {Comparison between the Binding of Ca2+ and Mg2+ to the Two High-Affinity Sites of Bacteriorhodopsin},
	journal = {The Journal of Physical Chemistry},
	volume = {99},
	year = {1995},
	note = {doi: 10.1021/j100029a043},
	month = {1995},
	pages = {11600 - 11604},
	publisher = {American Chemical Society},
	abstract = {See http://dx.doi.org/10.1021/j100029a043 for article{\textquoteright}s front page in lieu of an abstract },
	isbn = {0022-3654},
	doi = {doi: 10.1021/j100029a043},
	url = {http://dx.doi.org/10.1021/j100029a043},
	author = {Yoo, Seoung-Kyo and Awad, Elias S. and El-Sayed, Mostafa A}
}
@article {876,
	title = {The effect of different metal cation binding on the proton pumping in bacteriorhodopsin},
	journal = {Israel journal of chemistry},
	volume = {35},
	year = {1995},
	pages = {465-474},
	publisher = {Weizmann},
	abstract = {The first section of this paper is a detailed summary of studies made by us and others on metal cations binding to deionized bacteriorhodopsin (dIbR) and its variants. Our studies include the luminescence experiments of Eu3+ binding to dIbR and potentiometric studies of Ca2+ binding to dIbR, to deionized bR mutants, to bacterioopsin, and to dIbR with its C-terminus removed. The results suggest the presence of two classes of binding sites, one class has two high-affinity constants, and one has one low-affinity constant. For Ca2+ binding, there is one metal cation in each of the two high-affinity sites which are coupled to the charged aspartates 85 and 212 (known to be in the retinal cavity) but not coupled to each other. The low-affinity class can accommodate 0-6 Ca2+ ions and most of them are bound to the surface. Mg2+ has a slightly smaller value for its binding constant to the highest-affinity site. Thus, one expects more Ca2+ than Mg2+ bound to the two high-affinity sites. In the second section, we summarize our recent study on the effect of metal cation charge density (Ca2+, Mg2+, Eu3+, Tb3+, Ho3+, Dy3+) on the kinetics of both Schiff base deprotonation and proton transport to the extracellular surface. For all metal cations, the apparent rate constant of the slow components of the deprotonation process is the same as that for the transport process at 22 degrees C. The temperature studies, however, show this apparent equality to be fortuitous and to result from cancellation of the contribution of the energy and entropy of activation. Thus, while the entropy of activation is positive for the deprotonation process, it is negative for the proton transport process. These kinetic parameters depend weakly on the charge density, but in an opposite sense for the two processes. These results suggest that the deprotonation is not the rate-limiting step for the proton transport process. A possible mechanism is proposed in which a hydrated metal cation is used to induce the deprotonation of the protonated Schiff base and to dissociate one of its H2O molecules to donate the proton in the L-->M process.},
	isbn = {0021-2148},
	author = {El-Sayed, Mostafa A and Yang, Difei and Yoo, Seoung-Kyo and Zhang, N.}
}
@article {1286,
	title = {Enhancement of Metallic Silver Monomer Evaporation by the Adhesion of Polar Molecules to Silver Nanocluster Ions},
	journal = {The Journal of Physical Chemistry},
	volume = {99},
	year = {1995},
	note = {doi: 10.1021/j100019a061},
	month = {1995},
	pages = {7723 - 7730},
	publisher = {American Chemical Society},
	abstract = {View http://dx.doi.org/10.1021/j100019a061 for article{\textquoteright}s front page in lieu of an abstract},
	isbn = {0022-3654},
	doi = {doi: 10.1021/j100019a061},
	url = {http://dx.doi.org/10.1021/j100019a061},
	author = {Fagerquist, Clifton K. and Sensharma, Dilip K. and El-Sayed, Mostafa A and Rubio, Angel and Cohen, Marvin L.}
}
@article {1287,
	title = {Fourier Transform Infrared Spectroscopic Studies of the Effect of Ca2+ Binding on the States of Aspartic Acid Side Chains in Bacteriorhodopsin},
	journal = {The Journal of Physical Chemistry},
	volume = {99},
	year = {1995},
	note = {doi: 10.1021/j100019a066},
	month = {1995},
	pages = {7776 - 7781},
	publisher = {American Chemical Society},
	abstract = {View http://dx.doi.org/10.1021/j100019a066 for article{\textquoteright}s front page in lieu of an abstract},
	isbn = {0022-3654},
	doi = {doi: 10.1021/j100019a066},
	url = {http://dx.doi.org/10.1021/j100019a066},
	author = {Masuda, Satoshi and Nara, Masayuki and Tasumi, Mitsuo and El-Sayed, Mostafa A and Lanyi, Janos K.}
}
@article {1284,
	title = {Fourier-transform infrared spectroscopic comparison of cultured human fibroblast and fibrosarcoma cells},
	journal = {Proceedings of SPIE},
	volume = {2389},
	year = {1995},
	month = {1995},
	pages = {543},
	publisher = {SPIE},
	abstract = {Infrared vibration spectroscopy appears to be a more powerful technique for diagnosis than visible or UV spectroscopy. Advantages of IR spectra include: 1) vibrational motion has a smaller tissue absorption coefficient than electronic motion, 2) scattering of infrared radiation has a lower cross section than visible or UV light, (these two facts allow deeper penetration of IR radiation) and 3) vibration spectra provide a better fingerprint of chemical groups present in cells than the unresolved broad electronic spectrum of biological molecules. In the present work, Fourier-transform IR spectroscopy was used to compare cultured human fibroblast and malignant fibrosarcoma cells. Significant differences were observed by comparing the spectra of the normal cells with that of the cancer cells. the PO2 symmetric stretching mode at 1082cm-1 in the cancer cell is reduced in intensity. These observations are similar to those reported previously by Wong et al in comparing the IR spectra of pairs of normal and cancerous cells from the colon and cervix. However, the observed increase in the relative intensity of the symmetric to antisymmetric CH3 bending mode are only found in fibrosarcoma and basal cell carcinoma. The decrease in intensity of the CH2 bending mode relative to that of CH3 mode was observed only for fibrosarcoma cells. This finding with paired human fibroblast and fibrosarcoma cells suggests that fatty acid chains or side chains of protein in the cancer cells are partially degraded leading to more terminal carbon. It is also possible that changes in the environment upon carcinogenesis induces a change in the relative absorption cross sections for the CH3 and CH2 bending vibrations.
},
	doi = {10.1117/12.210030},
	url = {http://dx.doi.org/10.1117/12.210030},
	author = {Yang, Difei},
	editor = {Castro, D. and El Sayed, I.H. and El-Sayed, Mostafa A and Saxton, R. and Zhang, N.}
}
@article {1274,
	title = {A Fourier-transform infrared spectroscopic comparison of cultured human fibroblast and fibrosarcoma cells: a new method for detection of malignancies},
	journal = {Journal of clinical laser medicine \& surgery},
	volume = {13},
	year = {1995},
	pages = {55-59},
	abstract = {Infrared vibration spectroscopy appears to be a more powerful technique for tumor diagnosis than visible or UV spectroscopy. In the present work, Fourier-transform infrared (FTIR) spectroscopy was used to compare cultured normal fibroblast and fibrosarcoma cells. Significant differences were observed by comparing the spectra of the normal human cells with that of the cancer cells. The PO2 symmetric stretching mode at 1082 cm-1 is shifted to a higher frequency in the cancer cell and a broad band, whose center is located at 1064 cm-1 in the cancer cell is reduced in intensity. In addition, the decrease in intensity of the CH2 bending mode relative to that of CH3 mode is detectable only in the fibrosarcoma cell. This FTIR difference between fibroblast and fibrosarcoma cells suggests that either fatty acid chains or protein side chains of the cancer cells are partially degraded resulting in more terminal carbon (e.g., CH3). It is also possible that changes in the environment upon carcinogenesis induces a change in the relative absorption cross section for CH3 and CH2 bending vibrations. These results suggest that FTIR spectroscopy may become a promising and sensitive technique for tumor identification.},
	isbn = {1044-5471},
	author = {Yang, Difei and Castro, D. and El Sayed, I.H. and El-Sayed, Mostafa A and SAXTON, R.E. and ZHANG, N.Y.I.}
}
@article {1283,
	title = {On the molecular mechanisms of the rapid and slow solar-to-electric energy storage processes by the other natural photosynthetic system, bacteriorhodopsin},
	journal = {Pure and applied chemistry},
	volume = {67},
	year = {1995},
	pages = {149-149},
	publisher = {BLACKWELL SCIENTIFIC PUBLICATIONS},
	abstract = {Upon the absorption of solar energy by retinal in bacterioi..>dopsin highly specific photoisomerization of the retinal around the C13 -C14 bond takes place. This is followed by the formation of a number of intermediates resulting from conformational changes of the protein around the retinal which leads to the deprotonation of the protonated Schiff base of the retinylidene system. Thisis the switch of the proton pump which leads to the last step in the storage of solar energy in the form of electric energy by this photosynthetic system. The removal of metal cations from bR is found to inhibit the deprotonation process.
In the present paper we summarize the results of our studies and the others regarding two important questions in the conversion process: 1) what is(are) the molecular mechanism(s) of the protein catalysis of the photoisomerizationprocess and 2) what is the role of metal cations in the deprotonation process of the protonated Schiff base (the switch of the proton pump)? In order to answer the first question, the results of the subpicosecondphotoisomerization rate of retinal in bR and in a number of its relevant mutants are discussed in terms of the steric and electronic factors. In an effort to answer the second question,we discussed the results of the binding studies of Ca*+to bR, to its mutants and to bR after its C- terminus is cleaved. From these results and the results of Roux et al. on the 31P NMR of Nd3+ regenerated bR, we concluded that one or two metal cations strongly bound to the protein but not on the surface, are functionally important. The model in which these metal cation@)control the pK values of Aspartic acids in the 85 and 212 positions and that of the protonated Schiff base (PSB) during the photocycle is discussed.},
	isbn = {0033-4545},
	author = {El-Sayed, Mostafa A and Griffiths, Jennifer A. and Song, Li and Zhang, N.}
}
@article {1288,
	title = {Photofragment translational spectroscopy of Ibr at 304 nm:  Polarization dependence and dissociation dynamics},
	journal = {Journal of Chemical Physics},
	volume = {103},
	number = {16},
	year = {1995},
	note = {Times Cited: 11},
	month = {Oct 22},
	pages = {6999-7005},
	abstract = {The photodissociation dynamics of IBr has been studied at 304 nm by state-selective photofragment translational spectroscopy. Velocity distributions, anisotropy parameters, and relative quantum yields are obtained for the ground I(P-2(3/2)) and spin-orbit excited state I*(P-2(1/2)) iodine atoms, which are produced from photodissociation of IBr at this wavelength. Two sharp velocity distributions observed for the I channel suggest the two dissociation pathways that correlate with ground-state iodine formation. Based on the expected translational energy release and the energy separation between the peaks, the two distributions have been assigned to dissociation of IBr to form I(P-2(3/2))+Br(P-2(3/2)) and I(P-2(3/2))+Br*(P-2(1/2)) with the former channel appearing at higher translational energy. The I* distribution shows one strong peak indicating that there is one dominant channel for formation of I* atoms at this wavelength which has been assigned to dissociation of IBr to form I*(P-2(1/2))+Br(P-2(3/2)) with a quantum yield of 0.1. The I* signal formed from the I*(P-2(1/2))+Br*(P-2(1/2)) dissociation channel is observed very weakly. The observed anisotropy parameter indicates that the I+Br* product (beta=-0.7) is formed mainly from the perpendicular (1) Pi(1)(2341)<--X transition while the I*+Br channel (beta=1.8) is formed predominantly from the parallel 3 Pi(0+)(2341)<--X transition followed by curve crossing to the (3) Sigma(0+)(-)(2422) State. The recoil energy dependence of the anisotropy parameter in the I atom produced in the I+Br channel shows a positive beta value above maximum of the peak recoil energy and a negative value below the peak maximum of the recoil energy distribution. These results are interpreted in terms of the presence of more than one path for the formation of I+Br photoproduct with opposite polarization for their absorbing transitions, most likely the (3) Pi(0+)(2341)<--X and the (3) Pi(1)(2341)<--X transitions. The possible excited state dynamics which give the observed results are discussed in terms of the previously proposed potential energy diagrams for IBr and ICl. (C) 1995 American Institute of Physics.},
	isbn = {0021-9606},
	doi = {10.1063/1.470326},
	author = {Jung, Kwang-Woo and Griffiths, Jennifer A. and El-Sayed, Mostafa A}
}
@article {1268,
	title = {Retinal Isomer Composition in Some Bacteriorhodopsin Mutants under Light and Dark Adaptation Conditions},
	journal = {The Journal of Physical Chemistry},
	volume = {99},
	year = {1995},
	note = {doi: 10.1021/j100024a056},
	month = {1995},
	pages = {10052 - 10055},
	publisher = {American Chemical Society},
	abstract = {View http://dx.doi.org/10.1021/j100024a056 for the article{\textquoteright}s first page in lieu of an abstract},
	isbn = {0022-3654},
	doi = {doi: 10.1021/j100024a056},
	url = {http://dx.doi.org/10.1021/j100024a056},
	author = {Song, Li and Yang, Difei and El-Sayed, Mostafa A and Lanyi, Janos K.}
}
@book {1285,
	title = {Ultrafast Processes in Chemistry and Photobiology},
	year = {1995},
	publisher = {Blackwell Science},
	organization = {Blackwell Science},
	abstract = {This new volume continues the tradition of the {\textquoteright}Chemistry for the 21st Century{\textquoteright} Series in exploring areas of active research in chemistry today which are likely to have a profound effect on the science of chemistry in the future. Lasers have had, and will have, a positive impact on chemistry with the short pulse width of the laser enabling chemists to measure the primary processes of important chemical changes. This use of lasers to measure ultrafast processes in chemistry and photobiology is one of the most active as well as one of the most fundamental field of research. This volume presents expert contributions summarizing the state-of-the-art in this most important area.},
	isbn = {086542893X},
	author = {El-Sayed, Mostafa A and Tanaka, I. and Molin, I.U.N.}
}
@article {1282,
	title = {The Wavelength Dependence of the Rates of Internal Energy Redistribution during the Photodissociation of 3-Iodopyridine},
	journal = {The Journal of Physical Chemistry},
	volume = {99},
	year = {1995},
	note = {doi: 10.1021/j100019a024},
	month = {1995},
	pages = {7395 - 7406},
	publisher = {American Chemical Society},
	abstract = {View http://dx.doi.org/10.1021/j100019a024 for article{\textquoteright}s front page in lieu of an abstract},
	isbn = {0022-3654},
	doi = {doi: 10.1021/j100019a024},
	url = {http://dx.doi.org/10.1021/j100019a024},
	author = {Freitas, John E. and El-Sayed, Mostafa A and Hwang, Hyun Jin}
}
@article {1276,
	title = {Binding of, and Energy-Transfer Studies from Retinal to, Organic Cations in Regenerated Reduced Bacteriorhodopsin},
	journal = {The Journal of Physical Chemistry},
	volume = {98},
	year = {1994},
	note = {doi: 10.1021/j100088a040},
	month = {1994},
	pages = {9339 - 9344},
	publisher = {American Chemical Society},
	abstract = {See http://dx.doi.org/10.1021/j100088a040 for article{\textquoteright}s front page in lieu of an abstract},
	isbn = {0022-3654},
	doi = {doi: 10.1021/j100088a040},
	url = {http://dx.doi.org/10.1021/j100088a040},
	author = {Wu, Shuguang and El-Sayed, Mostafa A}
}
@article {1281,
	title = {Dynamics of Formation and Evaporation of Mixed Alkali Halide Nanocrystals: A Case of Comparable Lattice Energies},
	journal = {The Journal of Physical Chemistry},
	volume = {98},
	year = {1994},
	note = {doi: 10.1021/j100095a013},
	month = {1994},
	pages = {11316 - 11320},
	publisher = {American Chemical Society},
	abstract = {View http://dx.doi.org/10.1021/j100095a013 for article{\textquoteright}s front page in lieu of an abstract},
	isbn = {0022-3654},
	doi = {doi: 10.1021/j100095a013},
	url = {http://dx.doi.org/10.1021/j100095a013},
	author = {Ahmadi, Temer S. and El-Sayed, Mostafa A}
}
@article {1277,
	title = {pH Dependence of the Rate and Quantum Yield of the Retinal Photoisomerization in Bacteriorhodopsin},
	journal = {The Journal of Physical Chemistry},
	volume = {98},
	year = {1994},
	note = {doi: 10.1021/j100093a003},
	month = {1994},
	pages = {10674 - 10677},
	publisher = {American Chemical Society},
	abstract = {View http://dx.doi.org/10.1021/j100093a003 for article{\textquoteright}s front page in lieu of an abstract},
	isbn = {0022-3654},
	doi = {doi: 10.1021/j100093a003},
	url = {http://dx.doi.org/10.1021/j100093a003},
	author = {Logunov, Stephan L. and Song, Li and El-Sayed, Mostafa A}
}
@article {859,
	title = {The pH dependence of the subpicosecond retinal photoisomerization process in bacteriorhodopsin: evidence for parallel photocycles.},
	journal = {Biophysical journal},
	volume = {67},
	year = {1994},
	month = {1994 Nov},
	pages = {2008-12},
	abstract = {The pH dependence of the subpicosecond decay of the retinal photoexcited state in bacteriorhodopsin (bR) is determined in the pH range 6.8-11.3. A rapid change in the decay rate of the retinal photoexcited state is observed in the pH range 9-10, the same pH range in which a rapid change in the M412 formation kinetics was observed. This observation supports the previously proposed heterogeneity model in which parallel photocycles contribute to the observed pH dependence of the M412 formation kinetics in bR.},
	keywords = {Bacteriorhodopsins, Biophysical Phenomena, Biophysics, Hydrogen-Ion Concentration, Isomerism, Kinetics, Molecular Structure, Photochemistry, Retinaldehyde},
	issn = {0006-3495},
	doi = {10.1016/S0006-3495(94)80684-8},
	author = {Song, Li and Logunov, Stephan L. and Yang, Difei and El-Sayed, Mostafa A}
}
@article {1280,
	title = {Recording of transient gratings using the short lived bacteriorhodopsin photocycle intermediates},
	journal = {Advanced Materials},
	volume = {5},
	year = {1993},
	month = {1993},
	pages = {838 - 842},
	publisher = {WILEY-VCH Verlag GmbH},
	abstract = {Bacteriorhodopsin, a light-transducing protein in the purple membrane of Halobacterium halobium, has unique properties that make it a potentially attractive material for use in optical imaging and processing. A transient diffraction grating based on the K intermediate of the bacteriorhodopsin photocycle has been produced on the nanosecond time scale. The diffraction efficiency, which would be sufficient for pattern recognition for example, was measured and the intensity dependence assessed.},
	isbn = {1521-4095},
	doi = {10.1002/adma.19930051111},
	url = {http://dx.doi.org/10.1002/adma.19930051111},
	author = {Wu, Shuguang and Br{\"a}uchle, Christoph and El-Sayed, Mostafa A}
}
