@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 {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 {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 {1603,
	title = {An Ultraviolet Resonance Raman Spectroscopic Study of Cisplatin and Transplatin Interactions with Genomic DNA},
	journal = {Journal of Physical Chemistry B},
	year = {2017},
	keywords = {display},
	author = {Geng, J and et al.}
}
@article {1628,
	title = {The effect of plasmon resonance coupling in P3HT-coated silver nanodisk monolayers on their optical sensitivity},
	journal = {Journal of Materials Chemistry C},
	year = {2016},
	author = {Geldmeier, J. A. and et al.}
}
@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 {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 {1626,
	title = {Photoexcited surface frustrated Lewis pairs for heterogeneous photocatalytic CO2 reduction},
	journal = {J. Am. Chem. Soc.},
	year = {2016},
	author = {Ghuman, K. K. and et al.}
}
@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 {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 {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 {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 {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 {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 {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 {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 {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}
}
@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 {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 {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 {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 {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 {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 {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 {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 {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 {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 {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 {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 {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 {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 {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 {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 {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 {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}
}
