@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 {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 {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 {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 {1608, title = {Unraveling the nature of anomalously fast energy storage in T-Nb2O5}, journal = {Journal of the American Chemical Society }, year = {2017}, author = {Chen, D. and et al.} } @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 {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 {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 {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 {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.} } @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 {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 {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 {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 {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 {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 {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 {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 {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 {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 {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 {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 {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 {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 {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 {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 {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 {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 {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.} }