@article {1083,
	title = {Plasmonic Enhancement of Nonradiative Charge Carrier Relaxation and Proposed Effects from Enhanced Radiative Electronic Processes in Semiconductor-Gold Core-Shell Nanorod Arrays},
	journal = {Journal of Physical Chemistry C},
	volume = {115},
	number = {13},
	year = {2011},
	note = {Dreaden, Erik C. Neretina, Svetlana Qian, Wei El-Sayed, Mostafa A. Hughes, Robert A. Preston, John S. Mascher, Peter},
	month = {Apr},
	pages = {5578-5583},
	abstract = {Plasmonic field enhancement of nonradiative exciton relaxation rates in vertically aligned arrays of high aspect ratio CdTe-Au core-shell nanorods was investigated by transient absorption spectroscopy, computational electromagnetics, and kinetic modeling. Increasing shell thickness in the high aspect ratio nanorods was found to result in dramatic differences in polarization-dependent nonradiative exciton relaxation rates, which we attribute to differing mechanisms of plasmonic field enhancement associated with predominant ground- or excited-state absorption processes. These results are compared with previous investigations of low aspect ratio CdTe-Au core-shell nanorods, and overall conclusions regarding plasmonic enhancement of nonradiative relaxation rates in this system are presented. We propose that when the resonantly coupled dipolar plasmon field of the shell is polarized parallel to the ground-state absorption transition moment of the core, Auger recombination dominates carrier relaxation and slower second-order decay kinetics are observed. When contributions of the resonantly coupled plasmon field are nondipolar or orthogonal to the ground-state absorption transition moment of the core, excited-state absorption processes are believed to dominate and increasingly rapid first-order relaxation kinetics are observed. We find that these processes can vary greatly, depending on shell thickness and the orientation of the array, but are insensitive to aspect ratio. These investigations have significant implications in the design of photovoltaic and optoelectronic devices incorporating anisotropic plasmonic elements.},
	isbn = {1932-7447},
	doi = {10.1021/jp112129k},
	author = {Dreaden, Erik and Neretina, Svetlana and Qian, Wei and El-Sayed, Mostafa A and Hughes, Robert A and Preston, John S and Mascher, Peter}
}
@article {1077,
	title = {Plasmonic Field Effects on the Energy Transfer between Poly(p-phenyleneethynylene) Fluorescent Polymer and Au Nanocages},
	journal = {Journal of Physical Chemistry C},
	volume = {115},
	number = {26},
	year = {2011},
	note = {Mahmoud, M. A. El-Sayed, M. A.},
	month = {Jul},
	pages = {12726-12735},
	abstract = {Colloidal gold nanocages (AuNCs) with a wall length of 60 nm and wall thickness of 6 nm were prepared by the galvanic replacement method. The AuNCs were assembled into monolayers with different percents of surface coverage, using the Langmuir-Blodgett technique. The same technique was used to coat the assembled monolayers of AuNCs with another monolayer of poly(p-phenyleneethynylene) (PPE) fluorescent polymer. The surface plasmon resonance (SPR) spectrum of the AuNCs red-shifts as the percent of AuNCs coverage increases due to growth of the interparticle surface plasmon resonance field coupling as interparticle distance decreases. While after coating the AuNCs array with PPE, the SPR of all the AuNCs monolayers arrays were red-shifted to the same position (693 nm). This unsystematic red-shift behavior is based on the presence of two plasmon fields (inside and outside of AuNCs) and is described by discrete dipole approximation (DDA) simulation. The polymer fluorescence intensity is found to decrease when the polymer is deposited over the AuNCs. This observation is due to the energy transfer between the excited PPE and the AuNCs as well interchain energy transfer. Upon turning on the plasmonic field (exciting the surface plasmon resonance band), it is found that the fluorescence intensity of the polymer increased to a maximum value at AuNCs percent coverage of 10\% and then decreased as the interparticle separation distance decreased. DDA calculations showed that this is consistent with the dependence of the SPR field strength on the interparticle separation. Physically, this is a result of the interplay between the changes in the surface plasmon fields within the cavity of each nanoparticle and their external surface fields as a pair of AuNCs approach one another.},
	isbn = {1932-7447},
	doi = {10.1021/jp2007528},
	author = {Mahmoud, M A and El-Sayed, Mostafa A}
}
@article {1082,
	title = {Plasmonic photochemistry and photon confinement to the nanoscale},
	journal = {Journal of Photochemistry and Photobiology a-Chemistry},
	volume = {221},
	number = {2-3},
	year = {2011},
	note = {El-Sayed, Mostafa A.Si},
	month = {Jun},
	pages = {138-142},
	abstract = {This account gives a simple qualitative discussion of the confinement of the motion of electrons to the nanoscale. The mechanism by which gold and silver nanoparticles confine photons to the nanoscale, resulting in both the surface plasmon resonance and strong surface plasmon fields, is mentioned. Examples of different observations and applications of the plasmonic field enhancement of light scattering, absorption, photo-thermal and nonradiative processes studied in our group are summarized. (C) 2011 Elsevier B.V. All rights reserved.},
	isbn = {1010-6030},
	doi = {10.1016/j.jphotochem.2011.05.024},
	author = {El-Sayed, Mostafa A}
}
@article {1079,
	title = {Plasmonic Spheroidal Metal Nanoshells Showing Larger Tunability and Stronger Near Fields Than Their Spherical Counterparts: An Effect of Enhanced Plasmon Coupling},
	journal = {Journal of Physical Chemistry Letters},
	volume = {2},
	number = {5},
	year = {2011},
	note = {Hooshmand, Nasrin Jain, Prashant K. El-Sayed, Mostafa A.},
	month = {Mar},
	pages = {374-378},
	abstract = {Two of the most tunable nanostructure geometries for nanoplas monics include the metal nanoshell structure and the spheroidal geometry. We systematically investigate the effect of combining both geometries within the same nanostructure. Localized surface plasmon resonances (LSPRs) of spheroidal gold nanoshells are simulated as a function of their aspect ratio. The long-axis LSPR mode of a spheroidal nanoshell red shifts with decreasing shell thickness, similar to a spherical nanoshell. A higher aspect ratio spheroidal nanoshell shows a larger fractional LSPR red shift for the same thickness normalized by core dimensions. This is because coupling between the inner and outer surface plasmons of the nanoshell is stronger for the elongated spheroidal geometry as compared to that for the spherical case, increasing in strength with increasing aspect ratio. It is the result of this enhanced plasmon coupling that spheroidal nanoshells of aspect ratio 4 are over two times more tunable than spherical nanoshells. Also, the plasmonic field enhancement is an order of magnitude larger for the spheroidal nanoshells of aspect ratio 4 as compared to spherical nanoshells. These effects observed in the spheroidal nanoshell are analogous to those in a dimer of spheroidal nanopatides.},
	isbn = {1948-7185},
	doi = {10.1021/jz200034j},
	author = {Hooshmand, N. and Jain, Prashant K and El-Sayed, Mostafa A}
}
@article {1105,
	title = {Photoelectrochemical Water Oxidation Characteristics of Anodically Fabricated TiO(2) Nanotube Arrays: Structural and Optical Properties},
	journal = {Journal of Physical Chemistry C},
	volume = {114},
	number = {27},
	year = {2010},
	note = {Allam, Nageh K. El-Sayed, Mostafa A.},
	month = {Jul},
	pages = {12024-12029},
	abstract = {There are currently immense needs to optimize low-cost materials, such as TiO(2), so they can efficiently split water photoelectrochemically into hydrogen and oxygen, thus providing a clean energy fuel. To this end, the nature of the crystalline phase and the dimension of the photocatalyst are of crucial significance. In this study, films of 7 mu m long titania nanotube arrays were fabricated via anodization of titanium foil in formamide electrolytes containing NH(4)F and H(3)PO(4). Upon annealing the as-anodized nanotubes, the anatase-to-rutile phase transformation was found to start at 550 degrees C, which is about 120 degrees C above the temperature observed for the 500 nm long nanotube films, with the nanotube films remaining stable up to 580 degrees C. Analysis of the variation of crystallite size with annealing temperature along with XPS analysis of the films was used to investigate the reason behind this observation. UV-vis measurements showed that the absorption edges of the annealed samples were red shifted from that of the as-anodized sample. The stabilization of the anatase phase up to 550 degrees C, while keeping the tubular structure in place, is very significant as anatase is the most photoactive polymorph of titania. Besides, the 7 mu m long nanotubular structure provides a large surface medium for light utilization through scattering. Used as photoanodes to photoelectrochemically split water, the 580 degrees C crystallized nanotube arrays showed a three-electrode photoconversion efficiency of 10\% under UV illumination (100 mW/cm(2), 320-400 nm, 1 M KOH).},
	isbn = {1932-7447},
	doi = {10.1021/jp1037014},
	author = {Allam, N. K. and El-Sayed, Mostafa A}
}
@article {1095,
	title = {Plasmonic coupling in noble metal nanostructures},
	journal = {Chemical Physics Letters},
	volume = {487},
	number = {4-6},
	year = {2010},
	note = {Jain, Prashant K. El-Sayed, Mostafa A.},
	month = {Mar},
	pages = {153-164},
	abstract = {Noble metal nanostructures display unique and strongly enhanced optical properties due to the phenomenon of localized surface plasmon resonance (LSPR). In assemblies or complex noble metal nanostructures, individual plasmon oscillations on proximal particles can couple via their near-field interaction, resulting in coupled plasmon resonance modes, quite akin to excitonic coupling in molecular aggregates or orbital hybridization in molecules. In this frontier Letter we discuss how the coupling of plasmon modes in certain nanostructure geometries (such as nanoparticle dimers and nanoshells) allows systematic tuning of the optical resonance, and also the confinement and enhancement of the near-field, making possible improved refractive-index sensing and field-enhanced spectroscopy and photochemistry. We discuss the polarization, orientation, and distance-dependence of this near-field coupling especially the universal size-scaling of the plasmon coupling interaction. In addition to radiative properties, we also discuss the effect of inter-particle coupling on the non-radiative electron relaxation in noble metal nanostructures. (C) 2010 Elsevier B.V. All rights reserved.},
	isbn = {0009-2614},
	doi = {10.1016/j.cplett.2010.01.062},
	author = {Jain, Prashant K and El-Sayed, Mostafa A}
}
@article {1089,
	title = {Plasmonic Field Enhancement of the Bacteriorhodopsin Photocurrent during Its Proton Pump Photocycle},
	journal = {Journal of the American Chemical Society},
	volume = {132},
	number = {21},
	year = {2010},
	note = {Yen, Chun-Wan Chu, Li-Kang El-Sayed, Mostafa A.},
	month = {Jun},
	pages = {7250-+},
	abstract = {The proton pump photocycle of bacteriorhodopsin (bR) produces photocurrent on a microsecond time scale which is assigned to the deprotonation step forming the M(412) intermediate. The return of the M(412) intermediate to the bR ground state (bR(570)) has two pathways: (1) thermally via multiple intermediates (which takes 15 ms) or (2) by a more rapid and direct process by absorbing blue light (which takes hundreds of nanoseconds). By using nanoparticles (Ag, Ag-Au, and Au NPs) having different surface plasmon resonance extinction spectra, it is found that Ag NPs whose spectrum overlaps best with the M(412) absorption regions enhance the stationary photocurrent 15 times. This large enhancement is proposed to be due to the accelerated photoexcitation rate of the M(412) (in the presence of the plasmon field of the light in this region) as well as short-circuiting of the photocycle, increasing its duty cycles.},
	isbn = {0002-7863},
	doi = {10.1021/ja101301u},
	author = {Yen, C. W. and Chu, L. K. and El-Sayed, Mostafa A}
}
@article {1093,
	title = {Plasmonic Field Enhancement of the Exciton-Exciton Annihilation Process in a Poly(p-phenyleneethynylene) Fluorescent Polymer by Ag Nanocubes},
	journal = {Journal of the American Chemical Society},
	volume = {132},
	number = {8},
	year = {2010},
	note = {Mahmoud, Mahmoud A. Poncheri, Adam J. Phillips, Ronnie L. El-Sayed, Mostafa A.},
	month = {Mar},
	pages = {2633-2641},
	abstract = {Using the Langmuir-Blodgett (LB) technique, a poly(paraphenyleneethynylene) (PPE) fluorescent conjugated polymer was assembled on either a quartz substrate (system I) or on the surface of silver nanocube (AgNC) monolayers (system II). The fluorescence intensity of the polymer was studied in system I as a function of the surface density of the polymer sample when deposited on quartz substrates and in system II on the surface coverage of the underlying AgNC monolayers. In system I, a continual increase in the fluorescence intensity is observed as the surface density of excited polymer is increased. In system II, the fluorescence intensity of the polymer first increased until a threshold surface coverage of AgNC was reached, after which it decreased rapidly with increasing surface coverage in the AgNC monolayer. The exciting light intensity dependence is studied before and after this threshold in system II. The results suggest that one-photon processes were responsible for the increased intensity before the threshold, and two-photon processes were responsible for the rapid decrease in the polymer fluorescence intensity after the threshold. These observations are explained by the increase of the surface plasmon enhancement of the exciting light intensity as the nanoparticle surface coverage is increased. In turn, this increases the polymer absorption rate, which results in a continuous increase in the exciton density and is evident by an increase in the fluorescence intensity. At the threshold, the increased exciton density leads to an increase in the rate of exciton-exciton collisions, which leads to exciton-exciton annihilations. When this phenomenon becomes faster than the rate of fluorescence emission, an intensity decrease is observed. By exploiting the surface plasmon enhancement of absorption processes, we have observed the first exciton-exciton annihilation using a low-intensity Hg-lamp continuous wave source.},
	isbn = {0002-7863},
	doi = {10.1021/ja907657j},
	author = {Mahmoud, M A and Poncheri, A. J. and Phillips, R. L. and El-Sayed, Mostafa A}
}
@article {1091,
	title = {Polystyrene Microspheres: Inactive Supporting Material for Recycling and Recovering Colloidal Nanocatalysts in Solution},
	journal = {Journal of Physical Chemistry Letters},
	volume = {1},
	number = {1},
	year = {2010},
	note = {Mahmoud, M. A. Snyder, B. El-Sayed, M. A.},
	month = {Jan},
	pages = {28-31},
	abstract = {Alumina and silica have been the most commonly, used solid supports in the recovery of colloidal nanocatalysts in solution. In order to avoid possible involvement of the support in the catalytic mechanism, polystyrene microspheres are here demonstrated to be effective and nonreactive supports on which the nanocatalyst can be easily attached by using the swelling and shrinking properties of the polystyrene microspheres. The activation energy of the reduction of 4-nitrophenol with sodium borohydride on platinum nanocubes free in solution is comparable to those on polystyrene microspheres.},
	isbn = {1948-7185},
	doi = {10.1021/jz9000449},
	author = {Mahmoud, M A and Snyder, B. and El-Sayed, Mostafa A}
}
@article {1099,
	title = {Preparation of Cubic Pt Nanoparticles deposited on Alumina and their Application to Propene Hydrogenation},
	journal = {Chemcatchem},
	volume = {2},
	number = {3},
	year = {2010},
	note = {El-Sayed, Mostafa A. Yoo, Jung Whan},
	month = {Mar},
	pages = {268-271},
	isbn = {1867-3880},
	doi = {10.1002/cctc.200900247},
	author = {El-Sayed, Mostafa A and Yoo, J. W.}
}
@article {1107,
	title = {Photocatalysis in Gold Nanocage Nanoreactors},
	journal = {Journal of Physical Chemistry A},
	volume = {113},
	number = {16},
	year = {2009},
	note = {Yen, C. W. Mahmoud, M. A. El-Sayed, M. A.},
	month = {Apr},
	pages = {4340-4345},
	abstract = {The photodegradation of methyl orange was found to take place very efficiently using hollow Au nanocages which are known to have remaining Ag on their interior walls which can be oxidized to Ag(2)O. The degradation rate is found to be more efficient than photodegradation reaction using semiconductor nanomaterials, such as TiO(2) and ZnO. The reaction rate is found to increase by increasing the degree of Ag oxidation on the interior wall of the nanocages prior to the reaction and is a function of the nanocavity size and the pore density of the nanocage walls. As the cage size varies, it is found that the photocatalytic rate increases and then decreases with a maximum rate at nanoparticle size of 75 nm with a medium pore density-in the walls. All these results suggest that the catalysis is occurring inside the cavity, whose interior walls are covered with the Ag(2)O catalysts. Similar to the mechanism proposed in the degradation by the other semiconductors, we propose that the photodegradation mechanism involves the formation of the hydroxyl radical resulting from the photoexcitation of the Ag(2)O semiconductor. The observed results on the rate are discussion in terms of (1) the surface area of the inner wall covered with Ag (Ag(2)O), (2) the density and size of the pores in the walls, and (3) the cavity size of the nanoparticles.},
	isbn = {1089-5639},
	doi = {10.1021/jp811014u},
	author = {Yen, C. W. and Mahmoud, M A and El-Sayed, Mostafa A}
}
@article {1108,
	title = {Plasmonic Field Effect on the Hexacyanoferrate (III)-Thiosulfate Electron Transfer Catalytic Reaction on Gold Nanoparticles: Electromagnetic or Thermal?},
	journal = {Journal of Physical Chemistry C},
	volume = {113},
	number = {45},
	year = {2009},
	note = {Yen, Chun-Wan El-Sayed, Mostafa A.},
	month = {Nov},
	pages = {19585-19590},
	abstract = {The rate of the catalytic reaction between hexacyanoferrate (III) and thiosulfate on gold nanoparticles is found to increase when irradiated with light in resonance with surface plasmon absorption of the gold nanoparticles. Turning on the plasmonic field by turning on light at the surface plasmon extinction band wavelength could increase the rate by one of two possible mechanisms. In the first one, the electromagnetic field could chan-e its radiative or nonradiative electron transfer process (Mechanism I). In the other mechanism (Mechanism II), the strongly absorbed light by the gold nanoparticles is rapidly converted from light energy into heat energy that increases the temperature of the medium and increases the reaction rate. In order to determine which mechanism the plasmonic catalytic effect follows, we determined the activation energy of the reaction by heating the reaction solution via two different methods: irradiation at the surface plasmon resonance of the gold catalyst and by direct heating in a thermostat. The two activation energies are found to be the same, suggesting that the plasmonic field effect in this electron transfer reaction is thermally induced.},
	isbn = {1932-7447},
	doi = {10.1021/jp905186g},
	author = {Yen, C. W. and El-Sayed, Mostafa A}
}
@article {1129,
	title = {Photothermally excited coherent lattice phonon oscillations in plasmonic nanoparticles},
	journal = {European Physical Journal-Special Topics},
	volume = {153},
	year = {2008},
	note = {Huang, W. El-Sayed, M. A.14th International Conference on Photoacoustic and Photothermal Phenomena/1st US-Egypt Workshop on Photoacoustic and Photothermal PhenomenaJan 07-11, 2007Cairo, EGYPT},
	month = {Jan},
	pages = {325-333},
	abstract = {The photothermal property of (Ag and Au) plasmonic nanoparticles has brought about many important discoveries and applications in nanoscience and nanotechnology. In this review, we briefly summarize a photothermal effect, the coherent phonon oscillation, of plasmonic nanoparticles irradiated with ultrafast laser pulses of low power density. The coherent phonon oscillation is created in the nanoparticle by the ultrafast impulsive photothermal heating. The effects of size, shape, thickness, and interparticle interaction on the period of coherent phonon oscillations are discussed. The detection of the coherent lattice oscillation of metallic nanoparticles provides a powerful tool to characterize the mechanical and structural properties of nanostructures.},
	isbn = {1951-6355},
	doi = {10.1140/epjst/e2008-00456-x},
	author = {Huang, Wenyu and El-Sayed, Mostafa A}
}
@article {811,
	title = {Plasmon Field Effects on the Nonradiative Relaxation of Hot Electrons in an Electronically Quantized System: CdTe-Au Core-Shell Nanowires},
	journal = {Nano Letters},
	volume = {8},
	year = {2008},
	note = {doi: 10.1021/nl801303g},
	month = {2008},
	pages = {2410 - 2418},
	publisher = {American Chemical Society},
	abstract = {The intense electromagnetic fields of plasmonic nanoparticles, resulting from the excitation of their localized surface plasmon oscillations, are known to enhance radiative processes. Their effect on the nonradiative electronic processes, however, is not as well-documented. Here, we report on the enhancement of the nonradiative electronic relaxation rates in CdTe nanowires upon the addition of a thin gold nanoshell, especially at excitation energies overlapping with those of the surface plasmon oscillations. Some possible mechanisms by which localized surface plasmon fields can enhance nonradiative relaxation processes of any quantized electronic excitations are proposed.The intense electromagnetic fields of plasmonic nanoparticles, resulting from the excitation of their localized surface plasmon oscillations, are known to enhance radiative processes. Their effect on the nonradiative electronic processes, however, is not as well-documented. Here, we report on the enhancement of the nonradiative electronic relaxation rates in CdTe nanowires upon the addition of a thin gold nanoshell, especially at excitation energies overlapping with those of the surface plasmon oscillations. Some possible mechanisms by which localized surface plasmon fields can enhance nonradiative relaxation processes of any quantized electronic excitations are proposed.},
	isbn = {1530-6984},
	doi = {10.1021/nl801303g},
	url = {http://dx.doi.org/10.1021/nl801303g},
	author = {Neretina, Svetlana and Qian, Wei and Dreaden, Erik and El-Sayed, Mostafa A and Hughes, Robert A and Preston, John S and Mascher, Peter}
}
@article {1130,
	title = {Pulsed laser photothermal annealing and ablation of plasmonic nanoparticles},
	journal = {European Physical Journal-Special Topics},
	volume = {153},
	year = {2008},
	note = {Huang, W. El-Sayed, M. A.14th International Conference on Photoacoustic and Photothermal Phenomena/1st US-Egypt Workshop on Photoacoustic and Photothermal PhenomenaJan 07-11, 2007Cairo, EGYPT},
	month = {Jan},
	pages = {223-230},
	abstract = {In this review, we briefly summarize the photothermal properties of plasmonic nanoparticles. Several photothermal effects of plasmonic nanoparticles irradiated with ultrafast laser pulses of various powers are introduced. Plasmonic nanoparticles have been synthesized by pulsed laser ablation of bulk materials. Melting and ablation of nanoparticles have also been used to modify the shape and the size distribution of plasmonic nanoparticle samples. Under certain circumstances, another interesting observation using high power femtosecond laser irradiation of plasmonic nanoparticles is also included in this review, namely the flying, by propulsion of the plasmonic nanoparticles.},
	isbn = {1951-6355},
	doi = {10.1140/epjst/e2008-00432-6},
	author = {Huang, Wenyu and El-Sayed, Mostafa A}
}
@article {1135,
	title = {Peptide-conjugated gold nanorods for nuclear targeting},
	journal = {Bioconjugate Chemistry},
	volume = {18},
	number = {5},
	year = {2007},
	note = {Oyelere, Adegboyega K. Chen, Po C. Huang, Xiaohua El-Sayed, Ivan H. El-Sayed, Mostafa A.},
	month = {Sep-Oct},
	pages = {1490-1497},
	abstract = {Resonant electron oscillations on the surface of noble metal nanoparticles (Au, Ag, Cu) create the surface plasmon resonance (SPR) that greatly enhances the absorption and Rayleigh (Mie) scattering of light by these particles. By adjusting the size and shape of the particles from spheres to rods, the SPR absorption and scattering can be tuned from the visible to the near-infrared region (NIR) where biologic tissues are relatively transparent. Further, gold nanorods greatly enhance surface Raman scattering of adsorbed molecules. These unique properties make gold nanorods especially attractive as optical sensors for biological and medical applications. In the present work, gold nanorods are covalently conjugated with a nuclear localization signal peptide through a thioalkyl-triazole linker and incubated with an immortalized benign epithelial cell line and an oral cancer cell line. Dark field light SPR scattering images demonstrate that nanorods are located in both the cytoplasm and nucleus of both cell lines. Single cell micro-Raman spectra reveal enhanced Raman bands of the peptide as well as molecules in the cytoplasm and the nucleus. Further, the Raman spectra reveal a difference between benign and cancer cell lines. This work represents an important step toward both imaging and Raman-based intracellular biosensing with covalently linked ligand-nanorod probes.},
	isbn = {1043-1802},
	doi = {10.1021/bc070132i},
	author = {Oyelere, A. K. and Chen, P. C. and Huang, Xiaohua and El Sayed, I.H. and El-Sayed, Mostafa A}
}
@article {1142,
	title = {The potential use of the enhanced nonlinear properties of gold nanospheres in photothermal cancer therapy},
	journal = {Lasers in Surgery and Medicine},
	volume = {39},
	number = {9},
	year = {2007},
	note = {Huang, Xiaohua Qian, Wei El-Sayed, Ivan H. El-Sayed, Mostafa A.},
	month = {Oct},
	pages = {747-753},
	abstract = {Background and Objective: Laser photothermal therapy (PTT) is practiced at the moment using short laser pulses. The use of plasmonic nanoparticles as contrast agents can decrease the laser energy by using the optical property of the nanoparticles and improve the tumor selectivity by the molecular probes on the particle surface. In this study, we aim at selective and efficient PTT by exploiting the nonlinear optical properties of aggregated spherical gold nanoparticles conjugated to anti-epidermal growth factor receptor (anti-EGFR) antibodies using short NIR laser pulses. Study Design/Materials and Methods: Spherical gold nanoparticles are synthesized and conjugated to anti-EGFR antibodies to specifically target HSC oral cancer cells. The nanoparticles are characterized by micro-absorption spectra and dark field light scattering imaging. Photothermal destructions of control and nanoparticle treated cancer cells are carried out with a ferntosecond Ti:Sapphire laser at 800 nm with a pulse duration of 100 femtoseconds and repetition rate of 1 kHz. Results: The laser power threshold for the photothermal destruction of cells after the nanoparticle treatment is found to be 20 times lower than that required to destroy the cells in the normal PTT, that is, without nanoparticles. The number of destroyed cells is quadratically dependent on the laser power. The number of dead cells shows a nonlinear dependence on the concentration of gold nanoparticles that are specifically targeted to cancer cells. Conclusions: The energy threshold and selectivity of PTT can greatly benefit from the use of the plasmonic enhanced nonlinear optical processes of spherical gold nanoparticles conjugated to anti-EGFR antibodies. The quadratic dependence of the photothermal efficiency on the pulsed NIR laser power indicates a second harmonic generation or a two photon absorption process. The observed nonlinear dependence on the gold nanoparticle concentration suggests that aggregated nanospheres are responsible for the observed enhanced photothermal destruction of the cells.},
	isbn = {0196-8092},
	doi = {10.1002/lsm.20577},
	author = {Huang, Xiaohua and Qian, Wei and El Sayed, I.H. and El-Sayed, Mostafa A}
}
@article {1151,
	title = {Plasmon coupling in nanorod assemblies: Optical absorption, discrete dipole approximation simulation, and exciton-coupling model},
	journal = {Journal of Physical Chemistry B},
	volume = {110},
	number = {37},
	year = {2006},
	note = {Jain, Prashant K. Eustis, Susie El-Sayed, Mostafa A.},
	month = {Sep},
	pages = {18243-18253},
	abstract = {The shape anisotropy of nanorods gives rise to two distinct orientational modes by which nanorods can be assembled, i.e., end-to-end and side-by-side, analogous to the well-known H and J aggregation in organic chromophores. Optical absorption spectra of gold nanorods have earlier been observed to show a red-shift of the longitudinal plasmon band for the end-to-end linkage of nanorods, resulting from the plasmon coupling between neighboring nanoparticles, similar to the assembly of gold nanospheres. We observe, however, that side-by-side linkage of nanorods in solution shows a blue-shift of the longitudinal plasmon band and a red-shift of the transverse plasmon band. Optical spectra calculated using the discrete dipole approximation method were used to simulate plasmon coupling in assembled nanorod dimers. The longitudinal plasmon band is found to shift to lower energies for end-to-end assembly, but a shift to higher energies is found for the side-by-side orientation, in agreement with the optical absorption experiments. The strength of plasmon coupling was seen to increase with decreasing internanorod distance and an increase in the number of interacting nanorods. For both side-by-side and end-to-end assemblies, the strength of the longitudinal plasmon coupling increases with increasing nanorod aspect ratio as a result of the increasing dipole moment of the longitudinal plasmon. For both the side-by-side and end-to-end orientation, the simulation of a dimer of nanorods having dissimilar aspect ratios showed a longitudinal plasmon resonance with both a blue-shifted and a red-shifted component, as a result of symmetry breaking. A similar result is observed for a pair of similar aspect ratio nanorods assembled in a nonparallel orientation. The internanorod plasmon coupling scheme concluded from the experimental results and simulations is found to be qualitatively consistent with the molecular exciton coupling theory, which has been used to describe the optical spectra of H and J aggregates of organic molecules. The coupled nanorod plasmons are also suggested to be electromagnetic analogues of molecular orbitals. Investigation of the plasmon coupling in assembled nanorods is important for the characterization of optical excitations and plasmon propagation in these nanostructures. The surface plasmon resonance shift resulting from nanorod assembly also offers a promising alternative for analyte-sensing assays.},
	isbn = {1520-6106},
	doi = {10.1021/jp063879z},
	author = {Jain, Prashant K and Eustis, Susie and El-Sayed, Mostafa A}
}
@article {1163,
	title = {Partial dehydration of the retinal binding pocket and proof for photochemical deprotonation of the retinal Schiff base in bicelle bacteriorhodopsin crystals},
	journal = {Photochemistry and Photobiology},
	volume = {81},
	number = {6},
	year = {2005},
	note = {Sanii, LS El-Sayed, MA},
	month = {Nov-Dec},
	pages = {1356-1360},
	abstract = {In bicelle bacteriorhodopsin (bcbR) crystals, the protein has a different structure from both native bacteriorhodopsin (bR) and in-cubo bR (cbR) crystals. Recently, we studied the ability of bcbR crystals to undergo the photocycle upon laser excitation, characterized by the appearance of the M intermediate by single crystal resonance Raman spectroscopy. Calculation of the M lifetime by flash photolysis experiments demonstrated that in our bchR crystals, the M rise time is much faster than in the native or cbR crystals, with a decay time that is much slower than these other two forms. Although it is now known that the bcbR crystals are capable of photochemical deprotonation, it is not known whether photochemical deprotonation is the only way to create the deprotonated Schiff base in the bcbR crystals. We measured both the visible and Raman spectra of crystals dried under ambient lighting and dried in the dark in order to determine whether the retinal Schiff base is able to thermally deprotonate in the dark. In addition, changes in the visible spectrum of single bcbR crystals under varying degrees of hydration and light exposure were examined to better understand the retinal binding environment.},
	isbn = {0031-8655},
	doi = {10.1562/2005-03-09-ra-458},
	author = {Sanii, L. S. and El-Sayed, Mostafa A}
}
@article {1170,
	title = {Photothermal reshaping of prismatic Au nanoparticles in periodic monolayer arrays by femtosecond laser pulses},
	journal = {Journal of Applied Physics},
	volume = {98},
	number = {11},
	year = {2005},
	note = {Huang, WY Qian, W El-Sayed, MA},
	month = {Dec},
	abstract = {Prismatic gold nanoparticles in the periodic monolayer arrays prepared with nanosphere lithography technique can be reshaped with femtosecond laser pulses at different powers and wavelengths. As the power density of 400 nm femtosecond laser increases, the prismatic particle tips begin to round and the overall particle shape changes from a prism to a sphere with a tripodal intermediate. The formation of the tip-rounded nanoprisms is probably due to the dewetting properties of gold on quartz surface and the low melting temperature at the tips. The formation of the tripodal nanoparticles is attributed to the inhomogeneous heating and lattice rearrangement of the as-deposited nanoparticles to a metastable state, which is more stable than the prismatic shape but less stable than the spherical shape. With 800 nm femtosecond laser irradiation, only tip-rounded nanoprisms are observed and no spherical nanoparticles are formed at the laser powers used. This is most likely due to the blueshift of the plasmon absorption band for the transformed particles, so that they cannot absorb the required energy to overcome the barrier to make the spherical shape. With 700 nm femtosecond laser irradiation, the tip-rounded and the tripodal nanoparticles are formed and few spherical particles are observed at the higher laser power density. From the results of this work, it is shown that by changing the wavelength and power density of the femtosecond laser, one can control the final shape of the particles formed from the original prismatic nanoparticles.},
	isbn = {0021-8979},
	doi = {10.1063/1.2132515},
	author = {Huang, Wenyu and Qian, Wei and El-Sayed, Mostafa A}
}
@article {1162,
	title = {The protonation-deprotonation kinetics of the protonated Schiff base in bicelle bacteriorhodopsin crystals},
	journal = {Biophysical Journal},
	volume = {89},
	number = {1},
	year = {2005},
	note = {Sanii, LS Schill, AW Moran, CE El-Sayed, MA},
	month = {Jul},
	pages = {444-451},
	abstract = {In the recently published x-ray crystal structure of the "bicelle" bacteriorhodopsin (bbR) crystal, the protein has quite a different structure from the native and the in cubo bacteriorhodopsin (cbR) crystal. Instead of packing in parallel trimers as do the native membrane and the cbR crystals, in the bbR crystal the protein packs as antiparallel monomers. To date, no functional studies have been performed, to our knowledge, to investigate if the photocycle is observed in this novel protein packing structure. In this study, both Raman and time-resolved transient absorption spectroscopy are used to both confirm the presence of the photocycle and investigate the deprotonation-reprotonation kinetics of the Schiff base proton in the bbR crystal. The observed rates of deprotonation and reprotonation processes of its Schiff base have been compared to those observed for native bR under the same conditions. Unlike the previously observed similarity of the rates of these processes for cbR crystals and those for native bacteriorhodopsin (bR), in bbR crystals the rate of deprotonation has increased by 300\%, and the rate of reprotonation has decreased by nearly 700\%. These results are discussed in light of the changes observed when native bR is delipidated or monomerized by detergents. Both the change of the hydrophobicity of the environment around the protonated Schiff base and Asp(85) and Asp(96) (which could change the pK(a) values of proton donor-acceptor pairs) and the water structure in the bbR crystal are offered as possible explanations for the different observations.},
	isbn = {0006-3495},
	doi = {10.1529/biophysj.105.059675},
	author = {Sanii, L. S. and Schill, A. W. and Moran, C. E. and El-Sayed, Mostafa A}
}
@article {840,
	title = {Picosecond Self-Induced Thermal Lensing from Colloidal Silver Nanodisks},
	journal = {The Journal of Physical Chemistry B},
	volume = {108},
	year = {2004},
	note = {doi: 10.1021/jp049943z},
	month = {2004},
	pages = {5230 - 5234},
	publisher = {American Chemical Society},
	abstract = {The optical and nonradiative relaxation dynamics of 5 nm thick silver nanodisks with a 25 nm diameter have been investigated in an organic solvent by continuous wave (cw) and femtosecond pump?probe time-resolved spectroscopies. Several surface plasmon absorption bands are observed due to the disk shape of these particles. In the time-resolved experiments, the time dependence of the bleach resulting from femtosecond pulsed excitation is studied. On the 1?3 ps time scale, a decay resulting from electron?phonon relaxation is observed. On a longer time scale (>20 ps), a rise rather than a further decay of the bleach intensity is observed. This is shown to result from the formation of a thermal lens due to the induced thermal gradients produced from heating the organic solvent by the phonon?phonon relaxation processes of the photoexcited nanodisks.The optical and nonradiative relaxation dynamics of 5 nm thick silver nanodisks with a 25 nm diameter have been investigated in an organic solvent by continuous wave (cw) and femtosecond pump?probe time-resolved spectroscopies. Several surface plasmon absorption bands are observed due to the disk shape of these particles. In the time-resolved experiments, the time dependence of the bleach resulting from femtosecond pulsed excitation is studied. On the 1?3 ps time scale, a decay resulting from electron?phonon relaxation is observed. On a longer time scale (>20 ps), a rise rather than a further decay of the bleach intensity is observed. This is shown to result from the formation of a thermal lens due to the induced thermal gradients produced from heating the organic solvent by the phonon?phonon relaxation processes of the photoexcited nanodisks.},
	isbn = {1520-6106},
	doi = {10.1021/jp049943z},
	url = {http://dx.doi.org/10.1021/jp049943z},
	author = {Maillard, Mathieu and Pileni, Marie-Paule and Link, Stephan and El-Sayed, Mostafa A}
}
@article {1178,
	title = {Picosecond self-induced thermal lensing from colloidal silver nanodisks},
	journal = {Journal of Physical Chemistry B},
	volume = {108},
	number = {17},
	year = {2004},
	note = {Maillard, M Pileni, MP Link, S El-Sayed, MA},
	month = {Apr},
	pages = {5230-5234},
	abstract = {The optical and nonradiative relaxation dynamics of 5 unit thick silver nanodisks with a 25 nm diameter have been investigated in an organic solvent by continuous wave (cw) and femtosecond pump-probe time-resolved spectroscopies. Several surface plasmon absorption bands are observed due to the disk shape of these particles. In the time-resolved experiments, the time dependence of the bleach resulting from femtosecond pulsed excitation is studied. On the 1-3 ps time scale, a decay resulting from electron-phonon relaxation is observed. On a longer time scale (>20 ps), a rise father than a further decay of the bleach intensity is observed. This is shown to result from the formation of a thermal lens due to the induced thermal gradients produced from heating the organic solvent by the phonon-phonon relaxation processes of the photoexcited nanodisks.},
	isbn = {1520-6106},
	doi = {10.1021/jp049943z},
	author = {Maillard, Mathieu and Pileni, Marie-Paule and Link, Stephan and El-Sayed, Mostafa A}
}
@article {838,
	title = {Propylene hydrogenation over cubic Pt nanoparticles deposited on alumina},
	journal = {BULLETIN-KOREAN CHEMICAL SOCIETY},
	volume = {25},
	year = {2004},
	pages = {843-846},
	publisher = {Korean Chemical Society},
	abstract = {Pt nanoparticles loaded on alumina through an impregnation at room temperature was prepared using K2PtCl4 and acrylic acid as capping material. Transmission electron microscopy showed that the deposited Pt particles indicate ca. 80\% cubic shapes with a narrow distribution of 8-10 nm in size. Propylene hydrogenation over the catalyst has been carried out to evaluate their catalytic performance by the values of activation energy. It is determined from the initial rate, reaction order, and rate constant and is found to be 9.7 {\textpm} 0.5 kcal/mol. This value has been discussed by comparing to those of encapsulated- and truncated octahedral Pt nanoparticles deposited on alumina, respectively, to study influence of the particle size and shape, and capping material used
on the activation energy.},
	isbn = {0253-2964},
	url = {http://www.journal.kcsnet.or.kr/main/j_search/j_abstract_view.htm?code=B040616\&qpage=j_search\&spage=b_bkcs\&dpage=ar},
	author = {Yoo, J. W. and Lee, S.M. and Kim, H.T. and El-Sayed, Mostafa A}
}
@article {847,
	title = {Preparation and Growth Mechanism of Gold Nanorods (NRs) Using Seed-Mediated Growth Method},
	journal = {Chemistry of Materials},
	volume = {15},
	year = {2003},
	note = {doi: 10.1021/cm020732l},
	month = {2003},
	pages = {1957 - 1962},
	publisher = {American Chemical Society},
	isbn = {0897-4756},
	url = {http://dx.doi.org/10.1021/cm020732l},
	author = {Nikoobakht, Babak and El-Sayed, Mostafa A}
}
@article {1184,
	title = {Propene hydrogenation over truncated octahedral Pt nanoparticles supported on alumina},
	journal = {Journal of Catalysis},
	volume = {214},
	number = {1},
	year = {2003},
	note = {Yoo, JW Hathcock, DJ El-Sayed, MA},
	month = {Feb},
	pages = {1-7},
	abstract = {Colloidal Pt nanoparticles synthesized by a 1 : 5 concentration ratio of K2PtCl4 to polyacrylate were loaded on nanoporous alumina using the impregnation method at room temperature. The deposited Pt particles, present on the external surfaces of the support, were characterized by transmission electron microscopy, which indicated predominantly truncated octahedral (TO) shapes with a mean diameter of 10 nm. Their catalytic performance in the hydrogenation of propene at 30-80 degreesC was studied as a test reaction. The initial rate, reaction order, rate constant, activation energy, and turnover frequency were determined. The activation energy was found to be 8.4 +/- 0.2 kcal/mol, which is slightly lower than results reported for other platinum systems (10-14 kcal/mol). The TO platinum nanoparticles have atom-high surface steps, ledges, and kinks, and these atomic-scale fine structures are expected to decrease the activation energy. The reactivity of the surface atoms in this nanoparticle is so high that above 50 degreesC side reactions leading to complete surface poisoning take place within a few minutes. The effect of the polymer concentration of the polyacrylate-capped TO Pt/Al2O3 on the hydrogenation catalytic activity was also investigated. (C) 2003 Elsevier Science (USA). All rights reserved.},
	isbn = {0021-9517},
	doi = {10.1016/s0021-9517(02)00136-7},
	author = {Yoo, J. W. and Hathcock, D. J. and El-Sayed, Mostafa A}
}
@article {841,
	title = {Proton transfer reactions in native and deionized bacteriorhodopsin upon delipidation and monomerization},
	journal = {Biophysical journal},
	volume = {85},
	year = {2003},
	pages = {426-434},
	publisher = {Elsevier},
	abstract = {We have investigated the role of the native lipids on bacteriorhodopsin (bR) proton transfer and their connection with the cation-binding role. We observe that both the efficiency of M formation and the kinetics of M rise and decay depend on the lipids and lattice but, as the lipids are removed, the cation binding is a much less important factor for the proton pumping function. Upon 75\% delipidation using 3-[(cholamidopropyl)dimethylammonio]-propanesulfonate (CHAPS), the M formation and decay kinetics are much slower than the native, and the efficiency of M formation is \~{}30\%{\textendash}40\% that of the native. Upon monomerization of bR by Trition X-100, the efficiency of M recovers close to that of the native (depending on pH), M formation is \~{}10 times faster, and M decay kinetics are comparable to native at pH 7. The same results on the M intermediate are observed if deionized blue bR (deI bbR) is treated with these detergents (with or without pH buffers present), even though deionized blue bR containing all the lipids has no photocycle. This suggests that the cation(s) has a role in native bR that is different than in delipidated or monomerized bR, even so far as to suggest that the cation(s) becomes unimportant to the function as the lipids are removed.},
	isbn = {0006-3495},
	doi = {10.1016/S0006-3495(03)74487-7},
	url = {http://dx.doi.org/10.1016/S0006-3495(03)74487-7},
	author = {Heyes, C D and El-Sayed, Mostafa A}
}
@article {852,
	title = {The pump power dependence of the femtosecond relaxation of CdSe nanoparticles observed in the spectral range from visible to infrared},
	journal = {The Journal of chemical physics},
	volume = {116},
	year = {2002},
	pages = {3828},
	abstract = {The pump power dependence of the relaxation dynamics of CdSe nanoparticles (NPs) was studied with femtosecond pump probe spectroscopy at observation wavelengths of the first exciton transition at 560 nm, the near infrared (NIR) absorption at 2 μm, and the transient mid-infrared (IR) absorption at 4.5 μm. Excitation with less than one photon per particle leads to bleaching of the excitonic transitions, and the bleach intensity is initially linear to the pump power. At higher pump power the bleach intensity levels off, when complete saturation of the excitonic transition is reached. At the same time, increasing pump power causes an acceleration of the bleach decay, which is due to additional Auger processes when multiple excitons are formed in the NPs. In addition, the pump power effect was investigated for the NIR and IR regions, at 2 and 4.5 μm wavelength, respectively. Whereas the IR transients are very similar to the ones observed for the bleach, the NIR transients behave completely different. No pump power dependence was found for the transients at 2 μm when pumped in a power range from 0.5 to 5 μJ per pulse. The results show that the fs transients in the visible (bleach) and IR (absorption) regions are due to electron relaxation in the conduction band and the NIR transients are due to the relaxation of the hole. Furthermore, it suggests that in the investigated CdSe NPs, Auger processes act much more efficiently on the electrons than for the holes. },
	doi = {10.1063/1.1446851},
	url = {http://link.aip.org/link/doi/10.1063/1.1446851},
	author = {Burda, Clemens and Link, Stephan and Mohamed, MB and El-Sayed, Mostafa A}
}
@article {1215,
	title = {Photoluminescence of CdSe nanoparticles in the presence of a hole acceptor: n-butylamine},
	journal = {Journal of Physical Chemistry B},
	volume = {105},
	number = {15},
	year = {2001},
	note = {Landes, C Burda, C Braun, M El-Sayed, MA},
	month = {Apr},
	pages = {2981-2986},
	abstract = {Addition of butylamine to a solution of colloidal CdSe nanoparticles (NPs) caused a decrease in fluorescence intensity, with no effect on the picosecond bleach recovery of the exciton formation or on the luminescence dynamics. The relative fluorescence quantum yield was found to decrease with increasing butylamine concentration and to level off at high concentrations, but the fluorescence lifetimes were not influenced. The nonlinear concentration dependence of the fluorescence quantum yield did not follow the Stern-Volmer equation. This is in agreement with the observation that the CdSe luminescence lifetime was not affected by the addition of butylamine. A mechanism is proposed in which the emission observed in CdSe is assumed to result from the combination of surface-trapped electrons and holes. n-Butylamine occupies hole sites, thus blocking the recombination process, which results in decreasing the density of luminescent centers. These results will be discussed in terms of the nature of the binding sites of the amine on the nanoparticle surface.},
	isbn = {1089-5647},
	doi = {10.1021/jp0041050},
	author = {Landes, Christy F. and Burda, Clemens and Braun, Markus and El-Sayed, Mostafa A}
}
@article {1225,
	title = {Probing the primary event in the photocycle of photoactive yellow protein using photochemical hole-burning technique},
	journal = {Photochemistry and Photobiology},
	volume = {72},
	number = {5},
	year = {2000},
	note = {Mascianglioli, T Devanathan, S Cusanovich, MA Tollin, G El-Sayed, MA},
	month = {Nov},
	pages = {639-644},
	abstract = {Photochemical hole-burning spectroscopy was used to study the excited-state electronic structure of the 4-hydroxycinnamyl chromophore in photoactive yellow protein (PYP), This system Is known to undergo a trans-to-cis isomerization process on a femtosecond-to-picosecond time scale, similar to membrane-bound rhodopsins, and is characterized by a broad featureless absorbance at 446 nm, Resolved vibronic structure was observed for the hole-burned spectra obtained when PYP in phosphate buffer at pH 7 was frozen at low temperature and irradiated with narrow bandwidth laser light at 331 nm, The approximate homogeneous width of 752 cm(-1) could be calculated From the deconvolution of the hole-burned spectra leading to an estimated dephasing time of similar to 14 fs for the PYP excited-state structure. The resolved vibronic structure also enabled us to obtain an estimated change in the C=C stretching frequency, from 1663 cm(-1) in the ground state to similar to 1429 cm(-1) upon photoexcitation. The results obtained allowed us to speculate about the excited-state structure of PYP, We discuss the data for PYP in relation to the excited-state model proposed for the photosynthetic membrane protein bacteriorhodopsin, and use it to explain the primary event in the function of photoactive biological protein systems. Photoexcitation was also carried out at 475 nm, The vibronic structure obtained was quite different both in terms of the frequencies and Franck-Condon envelope. The origin of this spectrum was tentatively assigned.},
	isbn = {0031-8655},
	doi = {10.1562/0031-8655(2000)072<0639:ptpeit>2.0.co;2},
	author = {Mascianglioli, T. and Devanathan, S. and Cusanovich, M. A. and Tollin, G. and El-Sayed, Mostafa A}
}
@article {1221,
	title = {Proton polarizability of hydrogen-bonded network and its role in proton transfer in bacteriorhodopsin},
	journal = {Journal of Physical Chemistry A},
	volume = {104},
	number = {18},
	year = {2000},
	note = {Wang, JP El-Sayed, MA},
	month = {May},
	pages = {4333-4337},
	abstract = {Room-temperature time-resolved step-scan Fourier Transform Infrared (FTIR) spectroscopy has been used to study the photocycle of native bacteriorhodopsin (bR) suspension in both H2O and D2O. The kinetics of the retinal isomerization, and that of the protonation/deprotonation of the proton acceptor, Asp85, are compared in the mu s to Ins time domain. It is found that hydrogen/deuterium (H/D) isotope exchange does not significantly affect the kinetics of the retinal isomerization and relaxation processes. However, the protonation/deprotonation processes of Asp85 COO- become slower in D2O. We also studied the kinetics of the continuum absorbance change in the 1850-1800 cm(-1) frequency region, which has previously been proposed to correspond to the absorption of the delocalized proton that is involved in the proton transport to the surface during the photocycle. An H/D isotope shift of the frequency range of this continuum absorbance has been confirmed by the observation that the band in the 1850-1800 cm(-1) disappears in the photocycle of bR in D2O. These results could support the previous proposal that the intramolecular proton release pathway consists of an H-bonded network. Our results also suggest that the two independent processes, the transfer of a proton from the Schiff base to Asp85 and the release of a different proton to the extracellular surface, are closely coupled events.},
	isbn = {1089-5639},
	doi = {10.1021/jp994460u},
	author = {Wang, Jianping and El-Sayed, Mostafa A}
}
@article {1251,
	title = {Primary step in bacteriorhodopsin photosynthesis: Bond stretch rather than angle twist of its retinal excited-state structure},
	journal = {Journal of the American Chemical Society},
	volume = {120},
	number = {34},
	year = {1998},
	note = {Song, L El-Sayed, MA},
	month = {Sep},
	pages = {8889-8890},
	isbn = {0002-7863},
	doi = {10.1021/ja980390d},
	author = {Song, Li and El-Sayed, Mostafa A}
}
@article {1258,
	title = {Photofragment translational spectroscopy of CH2I2 at 304 nm: Polarization dependence and energy partitioning},
	journal = {Bulletin of the Korean Chemical Society},
	volume = {18},
	number = {12},
	year = {1997},
	note = {Jung, KW Ahmadi, TS El-Sayed, MA},
	month = {Dec},
	pages = {1274-1280},
	abstract = {The photodissociation dynamics of CH2I2 has been studied at 304 nm by state-selective photofragment translational spectroscopy. Velocity distributions, anisotropy parameters, and relative quantum yields are obtained for the ground I(P-2(3/2)) and spin-orbit excited state I*(P-2(1/2)) iodine atoms, which are produced from photodissociation of CH2I2 at this wavelength. These processes are found to occur via B-1 <-- A(1) type electronic transitions. The quantum yield of I*(P-2(1/2)) is determined to be 0.25, indicating that the formation of ground state iodine is clearly the favored dissociation channel in the 304 nm wavelength region. From the angular distribution of dissociation products, the anisotropy parameters are determined to be beta(I)=0.4 for the I(P-2(3/2)) and beta (I*)=0.55 for the I*(P-2(1/2)) which substantially differ from the limiting value of 1.13. The positive values of anisotropy parameter, however, show that the primary processes for I and I* formation channels proceed dominantly via a transition which is parallel to I-I axis. The above results are interpreted in terms of dual path formation of iodine atoms from two different excited states, i.e., a direct and an indirect dissociation via curve crossing between these states. The translational energy distributions of recoil fragments reveal that a large fraction of the available energy goes into the internal excitation of the CH2I photofragment; <E-int>/E-avl=0.80 and 0.82 for the I and I* formation channels, respectively. The quantitative analysis for the energy partitioning of available energy into the photofragments is used to compare the experimental results with the prediction of direct impulsive model for photodissociation dynamics.},
	isbn = {0253-2964},
	author = {Jung, Kwang-Woo and Ahmadi, Temer S. and El-Sayed, Mostafa A}
}
@article {1290,
	title = {Photofragment Translational Spectroscopy of ICl at 304 nm},
	journal = {The Journal of Physical Chemistry A},
	volume = {101},
	year = {1997},
	note = {doi: 10.1021/jp970837p},
	month = {1997},
	pages = {6562 - 6567},
	publisher = {American Chemical Society},
	abstract = {The photodissociation dynamics of ICl is studied at 304 nm by state-selective photofragment translational spectroscopy. Velocity distributions, anisotropy parameters, and relative quantum yields are obtained for the ground I(2P3/2) and spin?orbit excited state I*(2P1/2) iodine atoms, which are produced from photodissociation of ICl at this wavelength. Two sharp velocity distributions are observed for the I channel, suggesting the existence of two dissociation pathways that correlate with ground state iodine formation. Based on the expected translational energy release and the energy separation between those peaks, the two distributions are assigned to dissociation of ICl to I(2P3/2) + Cl(2P3/2) and to I(2P3/2) + Cl*(2P1/2); the former channel appears at higher translational energy. The distribution of I* also shows two strong peaks, indicating that there are two dominant channels for the formation of I* atoms at this wavelength which we assign to the dissociation of ICl forming I*(2P1/2) + Cl(2P3/2) and I*(2P1/2) + Cl*(2P1/2), respectively. The quantum yield of I*(2P1/2) is determined to be 0.30, indicating that the formation of ground state iodine is clearly the favored dissociation channel at 304 nm. The observed anisotropy in the angular distribution of dissociation products (?) indicates that the I* + Cl and I* + Cl* channels are formed predominantly from the parallel transition (? = 1.7 for both channels) while the I + Cl and I + Cl* products are formed mainly from perpendicular transitions (? = ?0.5). The decrease in the anisotropy parameter of the I formation channels from their limiting value of ?1 is attributed to the presence of more than one path for the formation of I + Cl/Cl* photoproducts with opposite polarization for their absorbing transitions. The possible excited state dynamics, which give the observed results, are discussed in terms of the previously proposed energy correlation diagram for ICl.The photodissociation dynamics of ICl is studied at 304 nm by state-selective photofragment translational spectroscopy. Velocity distributions, anisotropy parameters, and relative quantum yields are obtained for the ground I(2P3/2) and spin?orbit excited state I*(2P1/2) iodine atoms, which are produced from photodissociation of ICl at this wavelength. Two sharp velocity distributions are observed for the I channel, suggesting the existence of two dissociation pathways that correlate with ground state iodine formation. Based on the expected translational energy release and the energy separation between those peaks, the two distributions are assigned to dissociation of ICl to I(2P3/2) + Cl(2P3/2) and to I(2P3/2) + Cl*(2P1/2); the former channel appears at higher translational energy. The distribution of I* also shows two strong peaks, indicating that there are two dominant channels for the formation of I* atoms at this wavelength which we assign to the dissociation of ICl forming I*(2P1/2) + Cl(2P3/2) and I*(2P1/2) + Cl*(2P1/2), respectively. The quantum yield of I*(2P1/2) is determined to be 0.30, indicating that the formation of ground state iodine is clearly the favored dissociation channel at 304 nm. The observed anisotropy in the angular distribution of dissociation products (?) indicates that the I* + Cl and I* + Cl* channels are formed predominantly from the parallel transition (? = 1.7 for both channels) while the I + Cl and I + Cl* products are formed mainly from perpendicular transitions (? = ?0.5). The decrease in the anisotropy parameter of the I formation channels from their limiting value of ?1 is attributed to the presence of more than one path for the formation of I + Cl/Cl* photoproducts with opposite polarization for their absorbing transitions. The possible excited state dynamics, which give the observed results, are discussed in terms of the previously proposed energy correlation diagram for ICl.},
	isbn = {1089-5639},
	doi = {doi: 10.1021/jp970837p},
	url = {http://dx.doi.org/10.1021/jp970837p},
	author = {Jung, Kwang-Woo and Ahmadi, Temer S. and El-Sayed, Mostafa A}
}
@article {1264,
	title = {Photodissociation dynamics of iodobenzene by state-selective photofragment translational spectroscopy},
	journal = {Journal of Photochemistry and Photobiology A: Chemistry},
	volume = {102},
	year = {1996},
	pages = {13-20},
	publisher = {Elsevier},
	abstract = {State-selective photofragment translational spectroscopy is used to probe the detailed nature of the photodissociation dynamics of iodobenzene at 304 nm. Simultaneous determination of the recoil speed, the spatial anisotropy, and the final state of the iodine fragment reveals that three dissociation channels with different dynamical characteristics compete in the photodissociation of iodobenzene at 304 nm. Based on the observed energy partitioning between the internal and translational modes and the dissociation time td determined from the spatial anisotropy by using a rotational depolarization model, the three dissociation channels are assigned as follows. Two fast dissociation channels, which result in formation of I *(2P1/2) (td=0.4 ps, quantum yield Φ=0.005{\textpm}0.002) and high velocity I(2P3/2) (td=0.3 ps, Φ=0.70{\textpm}0.04), are due to a parallel transition to the repulsive 3Q0(n,σ*) state in the CI bond, followed by dissociation along the same state or curve crossing to the 1Q1 state respectively. A slow dissociation channel (td=0.5{\textendash}1.4 ps, Φ=0.30{\textpm}0.04) which produces low velocity I(2P3/2) is due to a parallel transition to the triplet π,π* state(s) in the phenyl ring that is predissociated by the repulsive n,σ* state(s). The dissociation times determined in the present work are in excellent agreement with those of the recent femtosecond real-time measurements by Cheng et al. at 278 nm},
	isbn = {1010-6030},
	doi = {10.1016/S1010-6030(96)04369-9},
	author = {Hwang, Hyun Jin and El-Sayed, Mostafa A}
}
@article {872,
	title = {Photoisomerization Quantum Yield and Apparent Energy Content of the K Intermediate in the Photocycles of Bacteriorhodopsin, Its Mutants D85N, R82Q, and D212N, and Deionized Blue Bacteriorhodopsin},
	journal = {The Journal of Physical Chemistry},
	volume = {100},
	year = {1996},
	note = {doi: 10.1021/jp9515242},
	month = {1996},
	pages = {2391 - 2398},
	publisher = {American Chemical Society},
	abstract = {The quantum yield of photoisomerization and the energy content of the K intermediate in the photocycle of bacteriorhodopsin and its mutants D85N, R82Q, and D212N and deionized blue bR were measured. Transient optical absorption and photoacoustic spectroscopy with excitation using 400 fs laser pulse were combined to obtain results. The spectroscopic characteristics of the excited state, the J and K intermediates in the photocycle of the mutants, and deionized blue bR were determined. The presence of both 13-cis and all-trans isomers in the ground state of light-adapted D85N, R82Q, and D212N and deionized blue bR makes extraction of the quantum yield for each isomer difficult. Thus, only average values of the quantum yield for these samples were determined. The replacement of charged groups in the vicinity of the retinal Schiff base was found to decrease the rate of the photoisomerization by up to 30 times, but with no signficant change in either the apparent quantum yield of the photoisomerization or the energy stored in the K intermediate. The results are discussed in terms of the different models for the excited and ground state potential surfaces of the retinal configuration in bacteriorhodopsin.The quantum yield of photoisomerization and the energy content of the K intermediate in the photocycle of bacteriorhodopsin and its mutants D85N, R82Q, and D212N and deionized blue bR were measured. Transient optical absorption and photoacoustic spectroscopy with excitation using 400 fs laser pulse were combined to obtain results. The spectroscopic characteristics of the excited state, the J and K intermediates in the photocycle of the mutants, and deionized blue bR were determined. The presence of both 13-cis and all-trans isomers in the ground state of light-adapted D85N, R82Q, and D212N and deionized blue bR makes extraction of the quantum yield for each isomer difficult. Thus, only average values of the quantum yield for these samples were determined. The replacement of charged groups in the vicinity of the retinal Schiff base was found to decrease the rate of the photoisomerization by up to 30 times, but with no signficant change in either the apparent quantum yield of the photoisomerization or the energy stored in the K intermediate. The results are discussed in terms of the different models for the excited and ground state potential surfaces of the retinal configuration in bacteriorhodopsin.},
	isbn = {0022-3654},
	url = {http://dx.doi.org/10.1021/jp9515242},
	author = {Logunov, Stephan L. and El-Sayed, Mostafa A and Song, Li and Lanyi, Janos K.}
}
@article {867,
	title = {Picosecond Dynamics of Colloidal Gold Nanoparticles},
	journal = {The Journal of Physical Chemistry},
	volume = {100},
	year = {1996},
	note = {doi: 10.1021/jp960484e},
	month = {1996},
	pages = {8053 - 8056},
	publisher = {American Chemical Society},
	abstract = {Colloidal gold nanoparticles with an average radius of 15 nm have a surface plasmon absorption band at 530 nm. Excitation by laser pulses of 450 fs duration, and wavelength of 600 or 380 nm ?bleached? the plasmon band and produced a transient absorption at the wings of the ?bleach? spectrum. The transient absorption was found to have a similar temporal behavior at different wavelengths. Analysis of their temporal behavior showed two time constants:? 2.5 ps, and a slower component of >50 ps. Laser excitation close to the plasmon band at 600 nm leads to the formation of ?hot? non-Fermi electronic distribution within the colloidal particles. Transient absorption from these ?hot? electrons led to different absorptions from that of the plasmon absorption of ?cold? electrons. The ?hot? electrons relax via electron?phonon coupling in 2.5 ps, and the phonon?phonon relaxation of the lattice occurs in >50 ps. At 380 nm excitation, the amplitude of the blue wing becomes smaller, and the slow component becomes longer, which could be due to possible excitation of the d-band electrons. These results are discussed in terms of Mie theory and a two-temperature model (TTM), and their consequences on the optical absorption spectrum.Colloidal gold nanoparticles with an average radius of 15 nm have a surface plasmon absorption band at 530 nm. Excitation by laser pulses of 450 fs duration, and wavelength of 600 or 380 nm ?bleached? the plasmon band and produced a transient absorption at the wings of the ?bleach? spectrum. The transient absorption was found to have a similar temporal behavior at different wavelengths. Analysis of their temporal behavior showed two time constants:? 2.5 ps, and a slower component of >50 ps. Laser excitation close to the plasmon band at 600 nm leads to the formation of ?hot? non-Fermi electronic distribution within the colloidal particles. Transient absorption from these ?hot? electrons led to different absorptions from that of the plasmon absorption of ?cold? electrons. The ?hot? electrons relax via electron?phonon coupling in 2.5 ps, and the phonon?phonon relaxation of the lattice occurs in >50 ps. At 380 nm excitation, the amplitude of the blue wing becomes smaller, and the slow component becomes longer, which could be due to possible excitation of the d-band electrons. These results are discussed in terms of Mie theory and a two-temperature model (TTM), and their consequences on the optical absorption spectrum.},
	isbn = {0022-3654},
	url = {http://dx.doi.org/10.1021/jp960484e},
	author = {Ahmadi, Temer S. and Logunov, Stephan L. and El-Sayed, Mostafa A}
}
@article {873,
	title = {Picosecond Electronic Relaxation in CdS/HgS/CdS Quantum Dot Quantum Well Semiconductor Nanoparticles},
	journal = {The Journal of Physical Chemistry },
	volume = {100},
	year = {1996},
	note = {doi: 10.1021/jp953708m},
	month = {1996},
	pages = {6381 - 6384},
	publisher = {American Chemical Society},
	abstract = {Subpicosecond photoexcitation of CdS/HgS/CdS quantum dot quantum well nanoparticles at wavelengths shorter than their interband absorption (390 nm) leads to a photobleach spectrum at longer wavelengths (440?740 nm). The photobleach spectrum changes and its maximum red-shifts with delay time. These results are explained by the rapid quenching of the initially formed laser-excited excitons by two types of energy acceptors (traps); one is proposed to be due to CdS molecules at the CdS/HgS interface, and the other trap is that present in the CdS/HgS/CdS well. The results of the excitation at longer wavelengths as well as the formation and decay of the bleach spectrum at different wavelengths support this description.Subpicosecond photoexcitation of CdS/HgS/CdS quantum dot quantum well nanoparticles at wavelengths shorter than their interband absorption (390 nm) leads to a photobleach spectrum at longer wavelengths (440?740 nm). The photobleach spectrum changes and its maximum red-shifts with delay time. These results are explained by the rapid quenching of the initially formed laser-excited excitons by two types of energy acceptors (traps); one is proposed to be due to CdS molecules at the CdS/HgS interface, and the other trap is that present in the CdS/HgS/CdS well. The results of the excitation at longer wavelengths as well as the formation and decay of the bleach spectrum at different wavelengths support this description.},
	isbn = {0022-3654},
	url = {http://dx.doi.org/10.1021/jp953708m},
	author = {Kamalov, Valey F. and Little, Reginald and Logunov, Stephan L. and El-Sayed, Mostafa A}
}
@article {1288,
	title = {Photofragment translational spectroscopy of Ibr at 304 nm:  Polarization dependence and dissociation dynamics},
	journal = {Journal of Chemical Physics},
	volume = {103},
	number = {16},
	year = {1995},
	note = {Times Cited: 11},
	month = {Oct 22},
	pages = {6999-7005},
	abstract = {The photodissociation dynamics of IBr has been studied at 304 nm by state-selective photofragment translational spectroscopy. Velocity distributions, anisotropy parameters, and relative quantum yields are obtained for the ground I(P-2(3/2)) and spin-orbit excited state I*(P-2(1/2)) iodine atoms, which are produced from photodissociation of IBr at this wavelength. Two sharp velocity distributions observed for the I channel suggest the two dissociation pathways that correlate with ground-state iodine formation. Based on the expected translational energy release and the energy separation between the peaks, the two distributions have been assigned to dissociation of IBr to form I(P-2(3/2))+Br(P-2(3/2)) and I(P-2(3/2))+Br*(P-2(1/2)) with the former channel appearing at higher translational energy. The I* distribution shows one strong peak indicating that there is one dominant channel for formation of I* atoms at this wavelength which has been assigned to dissociation of IBr to form I*(P-2(1/2))+Br(P-2(3/2)) with a quantum yield of 0.1. The I* signal formed from the I*(P-2(1/2))+Br*(P-2(1/2)) dissociation channel is observed very weakly. The observed anisotropy parameter indicates that the I+Br* product (beta=-0.7) is formed mainly from the perpendicular (1) Pi(1)(2341)<--X transition while the I*+Br channel (beta=1.8) is formed predominantly from the parallel 3 Pi(0+)(2341)<--X transition followed by curve crossing to the (3) Sigma(0+)(-)(2422) State. The recoil energy dependence of the anisotropy parameter in the I atom produced in the I+Br channel shows a positive beta value above maximum of the peak recoil energy and a negative value below the peak maximum of the recoil energy distribution. These results are interpreted in terms of the presence of more than one path for the formation of I+Br photoproduct with opposite polarization for their absorbing transitions, most likely the (3) Pi(0+)(2341)<--X and the (3) Pi(1)(2341)<--X transitions. The possible excited state dynamics which give the observed results are discussed in terms of the previously proposed potential energy diagrams for IBr and ICl. (C) 1995 American Institute of Physics.},
	isbn = {0021-9606},
	doi = {10.1063/1.470326},
	author = {Jung, Kwang-Woo and Griffiths, Jennifer A. and El-Sayed, Mostafa A}
}
@article {1277,
	title = {pH Dependence of the Rate and Quantum Yield of the Retinal Photoisomerization in Bacteriorhodopsin},
	journal = {The Journal of Physical Chemistry},
	volume = {98},
	year = {1994},
	note = {doi: 10.1021/j100093a003},
	month = {1994},
	pages = {10674 - 10677},
	publisher = {American Chemical Society},
	abstract = {View http://dx.doi.org/10.1021/j100093a003 for article{\textquoteright}s front page in lieu of an abstract},
	isbn = {0022-3654},
	doi = {doi: 10.1021/j100093a003},
	url = {http://dx.doi.org/10.1021/j100093a003},
	author = {Logunov, Stephan L. and Song, Li and El-Sayed, Mostafa A}
}
@article {859,
	title = {The pH dependence of the subpicosecond retinal photoisomerization process in bacteriorhodopsin: evidence for parallel photocycles.},
	journal = {Biophysical journal},
	volume = {67},
	year = {1994},
	month = {1994 Nov},
	pages = {2008-12},
	abstract = {The pH dependence of the subpicosecond decay of the retinal photoexcited state in bacteriorhodopsin (bR) is determined in the pH range 6.8-11.3. A rapid change in the decay rate of the retinal photoexcited state is observed in the pH range 9-10, the same pH range in which a rapid change in the M412 formation kinetics was observed. This observation supports the previously proposed heterogeneity model in which parallel photocycles contribute to the observed pH dependence of the M412 formation kinetics in bR.},
	keywords = {Bacteriorhodopsins, Biophysical Phenomena, Biophysics, Hydrogen-Ion Concentration, Isomerism, Kinetics, Molecular Structure, Photochemistry, Retinaldehyde},
	issn = {0006-3495},
	doi = {10.1016/S0006-3495(94)80684-8},
	author = {Song, Li and Logunov, Stephan L. and Yang, Difei and El-Sayed, Mostafa A}
}
