@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 {1120,
	title = {Can the observed changes in the size or shape of a colloidal nanocatalyst reveal the nanocatalysis mechanism type: Homogeneous or heterogeneous?},
	journal = {Topics in Catalysis},
	volume = {48},
	number = {1-4},
	year = {2008},
	note = {Narayanan, Radha Tabor, Christopher El-Sayed, Mostafa A.},
	month = {May},
	pages = {60-74},
	abstract = {The surface energy of metallic nanocrystals is relatively high compared to bulk materials due to the metal-metal bond deficiency of the surface atoms. This results in an insufficient chemical valency. In addition, smaller nanoparticles possess a higher degree of curvature, weakening, the bonding of their surface atoms. This is especially true for non-spherical shapes, which are comprised of a large number of sharp corner and edge sites. These atomic sites possess higher surface energies due to the lower number of shared bonds with the nanoparticle, resulting in instability of the surface atoms and rendering them physically unstable and chemically active. In many instances, the constant "bombardment" of these surface atoms by the solvent molecules as well as by the reactant molecules when these nanocrystals are in colloidal solution could lead to surface atom dissolution, both physically and/or chemically. This phenomenon could alter the functionality of the metallic colloidal nanoparticle from supplying catalytically active sites (in heterogeneous catalysis) to serving as a reservoir of catalytically active species to the solution (in homogeneous catalysis). In the latter type, if the atoms of the nanocatalyst appear in the products, the nanoparticle is no longer a catalyst but a reactant. In this review we attempt to answer the question raised in the title by examining our Previous work on the changes in size, shape, and other physical and chemical properties of colloidal transition metal nanoparticles during the nanocatalysis of two fundamentally different and important reactions: (1) the gentle electron-transfer reaction at room temperature involving the reduction of hexacyanoferrate (III) ions with thiosulfate ions and (2) the more harsh Suzuki cross-coupling reaction between phenylboronic acid and iodobenzene that takes place at 100 degrees C for 12 h. Changes in the nanoparticle dimensions were followed with TEM and HRTEM. Raman and FTIR spectroscopies were used to follow the chemical changes. For each change, we will use the above definition to see if the observed change can help us determine whether the catalysis is homogeneous or heterogeneous.},
	isbn = {1022-5528},
	doi = {10.1007/s11244-008-9057-4},
	author = {Narayanan, Radha and Tabor, C. E. and El-Sayed, Mostafa A}
}
@article {1123,
	title = {Comparative study of the assemblies and the resulting plasmon fields of Langmuir-Blodgett assembled monolayers of silver nanocubes and gold nanocages},
	journal = {Journal of Physical Chemistry C},
	volume = {112},
	number = {37},
	year = {2008},
	note = {Mahmoud, M. A. El-Sayed, M. A.},
	month = {Sep},
	pages = {14618-14625},
	abstract = {Silver nanocubes (72 nm) and gold nanocages (75 nm) were assembled by varying the average interstitial particle distances by the Langmuir-Blodgett technique. The shape of the surface pressure-area isotherms for the two types of nanoparticles are discussed in terms of the degree of surface capping of each nanoparticle which depends on the surface quality. Monolayer films formed at different surface pressures were transferred by the vertical dipping method to silicon and glass substrates where their optical spectra and SEM. images were examined. A red-shift of the strong plasmon peak maximum was observed as the average particle distance was decreased. From the SEM images, the morphology as well as the percent area of the substrate surface covered at different pressures was determined. A linear relationship was observed between the percent of covered area and the plasmon peak maximum, the slope of which reflects the average plasmon field felt by the nanoparticles. The increase in the average field with increasing percent covered area is a result of the decrease in the average nanoparticle separation and/or the increase in the number of nanoparticles in each cluster in the distribution formed. The strength of the plasmon field resulting from gold cages is found to be much higher than that from the silver cubes and increases as the gold wall thickness decreases. These results are discussed in terms of the coupling between the two separate fields of the cage wall surfaces.},
	isbn = {1932-7447},
	doi = {10.1021/jp8040499},
	author = {Mahmoud, M A and El-Sayed, Mostafa A}
}
@article {1141,
	title = {Cancer cells assemble and align gold nanorods conjugated to antibodies to produce highly enhanced, sharp, and polarized surface Raman spectra: A potential cancer diagnostic marker},
	journal = {Nano Letters},
	volume = {7},
	number = {6},
	year = {2007},
	note = {Huang, Xiaohua El-Sayed, Ivan H. Qian, Wei El-Sayed, Mostafa A.},
	month = {Jun},
	pages = {1591-1597},
	abstract = {Human oral cancer cells are found to assemble and align gold nanorods conjugated to anti-epidermal growth factor receptor (anti-EGFR) antibodies. Immnoconjugated gold nanorods and nanospheres were shown previously to exhibit strong Rayleigh (Mie) scattering useful for imaging. In the present letter, molecules near the nanorods on the cancer cells are found to give a Raman spectrum that is greatly enhanced (due to the high surface plasmon field of the nanorod assembly in which their extended surface plasmon fields overlap), sharp (due to a homogeneous environment), and polarized (due to anisotropic alignments). These observed properties can be used as diagnostic signatures for cancer cells.},
	isbn = {1530-6984},
	doi = {10.1021/nl070472c},
	author = {Huang, Xiaohua and El Sayed, I.H. and Qian, Wei and El-Sayed, Mostafa A}
}
@article {1136,
	title = {Change in titania structure from amorphousness to crystalline increasing photoinduced electron-transfer rate in dye-titania system},
	journal = {Journal of Physical Chemistry C},
	volume = {111},
	number = {26},
	year = {2007},
	note = {Nishikiori, Hiromasa Qian, Wei El-Sayed, Mostafa A. Tanaka, Nobuaki Fujii, Tsuneo},
	month = {Jul},
	pages = {9008-9011},
	abstract = {Thin titania gel films containing well-dispersed fluorescein dye were prepared by the sol-gel method and treated with steam to promote crystal growth of the titania particles. It is known that steam treatment converts the titania structure from amorphousness to crystalline. In the present study, such change is found to increase the rate of the photoinduced electron transfer from and to dispersed fluorescein dye molecules.},
	isbn = {1932-7447},
	doi = {10.1021/jp072625q},
	author = {Nishikiori, H. and Qian, Wei and El-Sayed, Mostafa A and Tanaka, N. and Fujii, T.}
}
@article {1150,
	title = {Calculated absorption and scattering properties of gold nanoparticles of different size, shape, and composition: Applications in biological imaging and biomedicine},
	journal = {Journal of Physical Chemistry B},
	volume = {110},
	number = {14},
	year = {2006},
	note = {Jain, PK Lee, KS El-Sayed, IH El-Sayed, MA},
	month = {Apr},
	pages = {7238-7248},
	abstract = {The selection of nanoparticles for achieving efficient contrast for biological and cell imaging applications, as well as for photothermal therapeutic applications, is based on the optical properties of the nanoparticles. We use Mie theory and discrete dipole approximation method to calculate absorption and scattering efficiencies and optical resonance wavelengths for three commonly used classes of nanoparticles: gold nanospheres, silica-gold nanoshells, and gold nanorods. The calculated spectra clearly reflect the well-known dependence of nanoparticle optical properties viz. the resonance wavelength, the extinction cross-section, and the ratio of scattering to absorption, on the nanoparticle dimensions. A systematic quantitative study of the various trends is presented. By increasing the size of gold nanospheres from 20 to 80 nm, the magnitude of extinction as well as the relative contribution of scattering to the extinction rapidly increases. Gold nanospheres in the size range commonly employed (similar to 40 nm) show an absorption cross-section 5 orders higher than conventional absorbing dyes, while the magnitude of light scattering by 80-nm gold nanospheres is 5 orders higher than the light emission from strongly fluorescing dyes. The variation in the plasmon wavelength maximum of nanospheres, i.e., from similar to 520 to 550 nm, is however too limited to be useful for in vivo applications. Gold nanoshells are found to have optical cross-sections comparable to and even higher than the nanospheres. Additionally, their optical resonances lie favorably in the near-infrared region. The resonance wavelength can be rapidly increased by either increasing the total nanoshell size or increasing the ratio of the core-to-shell radius. The total extinction of nanoshells shows a linear dependence on their total size, however, it is independent of the core/shell radius ratio. The relative scattering contribution to the extinction can be rapidly increased by increasing the nanoshell size or decreasing the ratio of the core/shell radius. Gold nanorods show optical cross-sections comparable to nanospheres and nanoshells, however, at much smaller effective size. Their optical resonance can be linearly tuned across the near-infrared region by changing either the effective size or the aspect ratio of the nanorods. The total extinction as well as the relative scattering contribution increases rapidly with the effective size, however, they are independent of the aspect ratio. To compare the effectiveness of nanoparticles of different sizes for real biomedical applications, size-normalized optical cross-sections or per micron coefficients are calculated. Gold nanorods show per micron absorption and scattering coefficients that are an order of magnitude higher than those for nanoshells and nanospheres. While nanorods with a higher aspect ratio along, with a smaller effective radius are the best photoabsorbing nanoparticles, the highest scattering contrast for imaging applications is obtained from nanorods of high aspect ratio with a larger effective radius.},
	isbn = {1520-6106},
	doi = {10.1021/jp057170o},
	author = {Jain, Prashant K and Lee, K. S. and El Sayed, I.H. and El-Sayed, Mostafa A}
}
@article {1164,
	title = {Carbon-supported spherical palladium nanoparticles as potential recyclable catalysts for the Suzuki reaction},
	journal = {Journal of Catalysis},
	volume = {234},
	number = {2},
	year = {2005},
	note = {Narayanan, R El-Sayed, MA},
	month = {Sep},
	pages = {348-355},
	abstract = {Carbon-supported PVP-Pd nanoparticles prepared by adsorption of colloidal PVP-Pd nanoparticles onto activated carbon are used as catalysts for the Suzuki reaction between phenylboronic acid and iodobenzene to form biphenyl. These carbon-supported nanoparticles result in a lower biphenyl yield during the first cycle than the colloidal Pd nanoparticles that we studied previously. The carbon-supported Pd nanoparticles retain 69\% of its activity upon recycling (second cycle), which is almost double the recycling potential observed in colloidal Pd nanoparticles (37\% retention of activity). In addition, the carbon-supported Pd nanoparticles retain 73 +/- 3\% of their catalytic activity during the second through fifth cycles of the Suzuki reaction, while the catalytic activity of the colloidal Pd nanoparticles greatly decreases during that time frame. The carbon support that the palladium nanoparticles are adsorbed onto helps to preserve its catalytic activity for longer time periods. The effect of catalysis and recycling on the nanoparticle size is also investigated. The average size of the carbon-supported palladium nanoparticles is 1.9 +/- 0.1 nm initially, 2.6 +/- 0.1 nm after the first cycle, and 3.1 +/- 0.1 nm after the second cycle. The continued growth of the supported nanoparticles suggests that the carbon support protects the palladium nanoparticles during the harsh Suzuki reaction and prevents aggregation and precipitation unlike the colloidal palladium nanoparticles. In addition, a narrow size distribution during the growth process (Ostwald ripening) is observed for the carbon-supported nanoparticles. This could be due to the adsorption method for preparing carbon-supported Pd nanoparticles because excess unaggregated palladium atoms will not be adsorbed onto the carbon support. (c) 2005 Elsevier Inc. All rights reserved.},
	isbn = {0021-9517},
	doi = {10.1016/j.jcat.2005.06.024},
	author = {Narayanan, Radha and El-Sayed, Mostafa A}
}
@article {1165,
	title = {Catalysis with transition metal nanoparticles in colloidal solution: Nanoparticle shape dependence and stability},
	journal = {Journal of Physical Chemistry B},
	volume = {109},
	number = {26},
	year = {2005},
	note = {Narayanan, R El-Sayed, MA},
	month = {Jul},
	pages = {12663-12676},
	abstract = {While the nanocatalysis field has undergone an explosive growth during the past decade, there have been very few studies in the area of shape-dependent catalysis and the effect of the catalytic process on the shape and size of transition metal nanoparticles as well as their recycling potential. Metal nanoparticles of different shapes have different crystallographic facets and have different fraction of surface atoms on their corners and edges, which makes it interesting to study the effect of metal nanoparticle shape on the catalytic activity of various organic and inorganic reactions. Transition metal nanoparticles are attractive to use as catalysts due to their high surface-to-volume ratio compared to bulk catalytic materials, but their surface atoms could be so active that changes in the size and shape of the nanoparticles could occur during the course of their catalytic function, which could also affect their recycling potential. In this Feature Article, we review our work on the effect of the shape of the colloidal nanocatalyst on the catalytic activity as well as the effect of the catalytic process on the shape and size of the colloidal transition metal nanocatalysts and their recycling potential. These studies provide important clues on the mechanism of the reactions we studied and also can be very useful in the process of designing better catalysts in the future.},
	isbn = {1520-6106},
	doi = {10.1021/jp051066p},
	author = {Narayanan, Radha and El-Sayed, Mostafa A}
}
@article {836,
	title = {Chemistry and properties of nanocrystals of different shapes},
	journal = {Chemical Reviews},
	volume = {105},
	year = {2005},
	pages = {1025-1102},
	publisher = {ACS Publications},
	isbn = {0009-2665},
	doi = {10.1021/cr030063a},
	url = {http://dx.doi.org/10.1021/cr030063a},
	author = {Burda, Clemens and Chen, X. and Narayanan, Radha and El-Sayed, Mostafa A}
}
@article {1172,
	title = {Chemistry curricula in the future},
	journal = {Chemical \& Engineering News},
	volume = {83},
	number = {20},
	year = {2005},
	note = {El-Sayed, MA},
	month = {May},
	pages = {6-6},
	isbn = {0009-2347},
	author = {El-Sayed, Mostafa A}
}
@article {1176,
	title = {Changing catalytic activity during colloidal platinum nanocatalysis due to shape changes: Electron-transfer reaction},
	journal = {Journal of the American Chemical Society},
	volume = {126},
	number = {23},
	year = {2004},
	note = {Narayanan, R El-Sayed, MA},
	month = {Jun},
	pages = {7194-7195},
	isbn = {0002-7863},
	doi = {10.1021/ja0486061},
	author = {Narayanan, Radha and El-Sayed, Mostafa A}
}
@article {1179,
	title = {Coherent vibrational oscillation in gold prismatic monolayer periodic nanoparticle arrays},
	journal = {Nano Letters},
	volume = {4},
	number = {9},
	year = {2004},
	note = {Huang, WY Qian, W El-Sayed, MA},
	month = {Sep},
	pages = {1741-1747},
	abstract = {We studied the ultrafast laser-induced coherent phonon oscillation in prismatic shaped gold nanoparticles assembled in monolayer periodic arrays by using the nanosphere lithographic technique. The amplitude and phase of the oscillation observed by ultrafast pump-probe transient spectroscopy is monitored as the wavelength of the dipolar surface plasmon absorption decreases. At a certain wavelength, the oscillation could not be observed. As the monitoring wavelength decreases further, the sign of the amplitude changes. From the wavelength at which the oscillation is not detected, the dependence of the absorption maxima on the size of the nanoparticles, the changes in the nanoparticle size are estimated during its oscillation. This large change in the size of the prismatic nanoparticle compared to the small change reported previously for the nanosphere oscillations is discussed.},
	isbn = {1530-6984},
	doi = {10.1021/nl048875p},
	author = {Huang, Wenyu and Qian, Wei and El-Sayed, Mostafa A}
}
@article {1190,
	title = {Characterization of pt nanoparticles encapsulated in Al2O3 and their catalytic efficiency in propene hydrogenation},
	journal = {Journal of Physical Chemistry A},
	volume = {106},
	number = {10},
	year = {2002},
	note = {Yoo, JW Hathcock, D El-Sayed, MA},
	month = {Mar},
	pages = {2049-2054},
	abstract = {Pt nanoparticles supported in nanoporous Al2O3 catalyst are prepared by reduction of K2PtCl4 solution using 112 in the presence of Al2O3 and poly(acrylic acid) as capping; material. After thorough washing with water to remove Pt nanoparticles located on the external surface of the Al2O3 and drying at 70 degreesC for 12 h, they were used in propene hydrogenation to evaluate catalytic activity as measured by the value of the activation energy in the temperature range between 30 and 90 degreesC. The Pt nanoparticles are characterized by using transmission electron microscopy (TEM). The particles in Pt/Al2O3 are found to be encapsulated and uniformly dispersed inside the Al2O3; however, the size and shapes are not clearly seen. After extraction of the Pt nanoparticles from the Al2O3 channels by using an ethanol-diluted HF solution, various shapes such as truncated octahedral, cubic, tetrahedral, and spherical with a size around 5 nm are observed. The encapsulated particles have various shapes but are smaller in size than those prepared in K2PtCl4 solution with polyacrylate in the absence of Al2O3. Using FT-IR studies, the capping material initially used in Pt/Al2O3 is not found in the Al2O3 channels. This might be due to the fact that the polymer (average MW 2100) is too large to be accommodated within the Al2O3 pores. The nanopores of Al2O3 have several roles in the synthesis of these nanoparticles. It allows for uniform dispersion and encapsulation of Pt nanoparticles. It controls the Pt sizes with narrow distribution that is determined by the pore dimension (5.8 nm). It protects against metal particle aggregation and produces various shapes even in the absence of the capping material. Using these Pt nanoparticles, the catalysis of hydrogenation of propene gas was studied. The initial rates, reaction order, rate constants, and activation energy for the hydrogenation are determined by use of mass spectrometric techniques. The activation energy is found to be 5.7 kcal/mol, which is about one-half that previously reported for catalysis by Pt metal deposited in SiO2 and TiO2 synthesized by using H2PtCl6 and Pt(allyl)(2) by impregnation method.},
	isbn = {1089-5639},
	doi = {10.1021/jp0121318},
	author = {Yoo, J. W. and Hathcock, D. J. and El-Sayed, Mostafa A}
}
@article {1191,
	title = {Comparison of the dynamics of the primary events of bacteriorhodopsin in its trimeric and monomeric states},
	journal = {Biophysical Journal},
	volume = {83},
	number = {3},
	year = {2002},
	note = {Wang, JP Link, S Heyes, CD El-Sayed, MA},
	month = {Sep},
	pages = {1557-1566},
	abstract = {In this paper, femtosecond pump-probe spectroscopy in the visible region of the spectrum has been used to examine the ultrafast dynamics of the retinal excited state in both the native trimeric state and the monomeric state of bacteriorhodopsin (bR). It is found that the excited state lifetime (probed at 490 nm) increases only slightly upon the monomerization of bR. No significant kinetic difference is observed in the recovery process of the bR ground state probed at 570 nm nor in the fluorescent state observed at 850 nm. However, an increase in the relative amplitude of the slow component of bR excited state decay is observed in the monomer, which is due to the increase in the concentration of the 13-cis retinal isomer in the ground state of the light-adapted bR monomer. Our data indicate that when the protein packing around the retinal is changed upon bR monomerization, there is only a subtle change in the retinal potential surface, which is dependent on the charge distribution and the dipoles within the retinal-binding cavity. In addition, our results show that 40\% of the excited state bR molecules return to the ground state on three different time scales: one-half-picosecond component during the relaxation of the excited state and the formation of the J intermediate, a 3-ps component as the J changes to the K intermediate where retinal photoisomerization occurs, and a subnanosecond component during the photocycle.},
	isbn = {0006-3495},
	author = {Wang, Jianping and Link, Stephan and Heyes, C D and El-Sayed, Mostafa A}
}
@article {853,
	title = {The correlation between emission in freshly prepared porous silicon and the carrier density in silicon water},
	journal = {Asian Journal of Spectroscopy},
	volume = {6},
	year = {2002},
	author = {Zou, Bingsuo and Wang, Jianping and El-Sayed, Mostafa A}
}
@article {1236,
	title = {Comparison between the polarized Fourier-transform infrared spectra of aged porous silicon and amorphous silicon dioxide films on Si (100) surface},
	journal = {Journal of Molecular Structure},
	volume = {508},
	number = {1-3},
	year = {1999},
	note = {Wang, JP Zou, BS El-Sayed, MA},
	month = {Sep},
	pages = {87-96},
	abstract = {The s- and p-polarized Fourier transform infrared spectra were measured for an aged porous silicon (PS) film on Si (100) surface. The asymmetric stretching and symmetric stretching modes as well as the bending or rocking mode of the Si-O-Si group are studied. The deconvoluted spectra in Si-O-Si asymmetric stretching frequency region at different polarization directions show two pairs of vibrational modes, and can be assigned to the longitudinal-optic (LO) and transverse-optic (TO) pair of the corresponding vibrational modes. The smaller LO-TO pair splitting, the broader bandwidth, and the lower polarization ratio of the PS vibration bands as compared with those observed in an a-SiO2 film on Si wafer, suggest a less ordered SiO2 structure and a shorter range of coulombic interaction in PS. (C) 1999 Elsevier Science B.V. All rights reserved.},
	isbn = {0022-2860},
	doi = {10.1016/s0022-2860(99)00003-4},
	author = {Wang, Jianping and Zou, Bingsuo and El-Sayed, Mostafa A}
}
@article {1235,
	title = {Crystallographic facets and shapes of gold nanorods of different aspect ratios},
	journal = {Surface Science},
	volume = {440},
	number = {1-2},
	year = {1999},
	note = {Wang, ZL Mohamed, MB Link, S El-Sayed, MA},
	month = {Oct},
	pages = {L809-L814},
	abstract = {Crystal structures of gold nanorods synthesized electrochemically using micelles as a capping material have been studied by high-resolution transmission electron microscopy. Short gold nanorods with aspect ratios of 3-7 are enclosed mainly by (100) and (110) facets and their axial growth direction is [001], whereas long gold nanorods of aspect ratios 20-35 are dominated by (111) and (110) facets and their growth axial direction is (112). The short rods are the dominant constituents, whereas the long rods are observed occasionally. Spherical-like Au particles with equivalent mass to the short rods are dominated by (111) and (100) facets with shapes of truncated octahedra, icosahedra and decahedra. The unique (110) facets of Au nanorods are expected to have interesting surface properties. (C) 1999 Elsevier Science B.V. All rights reserved.},
	isbn = {0039-6028},
	doi = {10.1016/s0039-6028(99)00865-1},
	author = {Wang, Z.L. and Mohamed, MB and Link, Stephan and El-Sayed, Mostafa A}
}
@article {1257,
	title = {Charge separation effects on the rate of nonradiative relaxation processes in quantum dots quantum well heteronanostructures},
	journal = {Journal of Physical Chemistry A},
	volume = {102},
	number = {33},
	year = {1998},
	note = {Little, RB Burda, C Link, S Logunov, S El-Sayed, MA},
	month = {Aug},
	pages = {6581-6584},
	abstract = {Using time-resolved optical hole (oh)-burning techniques with femtosecond lasers, the time dependence of the spectral diffusion of the oh is examined for both the CdS quantum dot (QD) and the CdS/HgS/CdS quantum dot quantum well (QDQW) nanoparticles. It is found that the nonradiative relaxation of the optical hole is at least 3 orders of magnitude slower in the QDQW than in the QD system. Analysis of the second derivative of the broad transient bleach spectrum of the QDQW system in the 1.6-2.5 eV energy region at 50 fs delay time is found to have a minimum at 2.1 eV, corresponding to a minimum in the radiative probability. Around this energy, the rise and decay times of the transient bleach in the spectrum an found to change greatly. These results suggest that spectral diffusion in the QDQW is a result of relaxation from high- to low-energy exciton states, involving an intervening dark state at an energy of similar to 2.0 eV. The energies of the maxima and minimum of the second-derivative curve are found to be in good agreement with recent theoretical calculations by Jaskolski and Bryant(1) of the energies of the radiative and dark charge-separated state, respectively. In the latter, the hole is in the CdS clad and the electron is in the HgS well. The slow nonradiative relaxation processes involving this state are expected to be slow owing to the large change in the charge carrier effective masses as they cross from the CdS clad to the HgS well.},
	isbn = {1089-5639},
	doi = {10.1021/jp9822687},
	author = {Little, Reginald and Burda, Clemens and Link, Stephan and Logunov, Stephan L. and El-Sayed, Mostafa A}
}
@article {1259,
	title = {A Comparison of the Photoelectric Current Responses Resulting from the Proton Pumping Process of Bacteriorhodopsin under Pulsed and CW Laser Excitations},
	journal = {The Journal of Physical Chemistry B},
	volume = {101},
	year = {1997},
	note = {doi: 10.1021/jp972475r},
	month = {1997},
	pages = {10599 - 10604},
	publisher = {American Chemical Society},
	abstract = {When excited with a pulsed laser, an electric field-oriented bacteriorhodopsin (bR) film on an indium-tin oxide (ITO) conductive electrode generates a photocurrent composed of at least three different components:  B1 (<100 ps), B2 (60 μs), and B3 (ms). When excited with an electronic shutter modulated CW light pulse (>200 ms in duration), a differential photocurrent (components D1 and D2 with decay times in milliseconds) is observed from the bR film. D1 is observed when the CW light is turned on, and D2 is observed when the CW light is turned off. In this paper, we compare the amplitudes and lifetimes of B2, B3, and D1 at various values of pH and ionic strength of the electrolyte solution in which the photocurrent is measured. It is found that changing the film orientation changes the polarity (sign) of B1 and B2, while it does not affect the polarity of B3 and D1. It is also found that B3 and D1 change their polarity upon changing the pH of electrolyte solution, whereas B1 and B2 do not. These results suggest that the origin of B3 and D1 is different from that of B1 and B2. Our results suggest that B3 and D1 are due to the formation of a transient proton capacitor between the two ITO electrodes resulting from the proton pumping in bR. The magnitude and sign of B3 and D1 are determined by the transient proton concentration change (accumulation or disappearance) occurring near the bR-modified ITO electrode interface on the millisecond time scale. The change of sign in B3 and D1 as a function of pH is due to the sequence of proton release/uptake in the bR photocycle:  It first releases protons into the aqueous solution at high pH, while it first takes up protons from the aqueous solution at low pH. The effects of buffer and ionic strength on B3 and D1 are discussed in terms of the kinetics of proton release/uptake and of the transportation of positive and negative ions in the electrolyte solution.},
	isbn = {1520-6106},
	url = {http://dx.doi.org/10.1021/jp972475r},
	author = {Wang, Jianping and Song, Li and Yoo, Seoung-Kyo and El-Sayed, Mostafa A}
}
@article {1270,
	title = {Calcium and Magnesium Binding in Native and Structurally Perturbed Purple Membrane},
	journal = {The Journal of Physical Chemistry},
	volume = {100},
	year = {1996},
	note = {doi: 10.1021/jp952951i},
	month = {1996},
	pages = {929 - 933},
	publisher = {American Chemical Society},
	abstract = {The number and identity of the metal cations bound to wild-type bacteriorhodopsin (bR) are determined by using inductively coupled plasma mass spectrometry (ICP-MS) and ICP emission techniques. The results indicate that there at ≈2 total Ca2+ and Mg2+ per bR molecule with a ratio of ≈3:1 Ca2+ to Mg2+. This observed ratio is found to agree with the calculated ratio using previously determined binding constants for the two high affinity sites of Ca2+ to deionized bR (Zhang; et al. Biophys. J. 1992, 61, 1201). This suggests that the high-affinity binding sites in deionized bR are similar to those in native bR. Structural perturbation of the native membrane by cleavage of the C-terminus decreases the number of ions per bR to 1.4. The observed ratio of total ions in this sample to total ions in bR is found to agree with that calculated using known binding constants for each. The results on the number of metal cations/bR and their ratio in bacterio-opsin agrees with the calculated number using previously observed binding constants in deionized bO (Yang; et al. Biophys J., in press) only if one assumes that the second high-affinity site (not the first) is removed by retinal removal. Removal of 75\% of the lipids from the purple membrane is found to greatly reduce the number of metal cations from 2 to 0.16. This suggest that if metal cations are in the two high-affinity sites (which are the only type of binding sites evident in our native bR sample), the removal of lipids, known to change the protein tertiary structure, changes also the metal ion binding sites.The number and identity of the metal cations bound to wild-type bacteriorhodopsin (bR) are determined by using inductively coupled plasma mass spectrometry (ICP-MS) and ICP emission techniques. The results indicate that there at ≈2 total Ca2+ and Mg2+ per bR molecule with a ratio of ≈3:1 Ca2+ to Mg2+. This observed ratio is found to agree with the calculated ratio using previously determined binding constants for the two high affinity sites of Ca2+ to deionized bR (Zhang; et al. Biophys. J. 1992, 61, 1201). This suggests that the high-affinity binding sites in deionized bR are similar to those in native bR. Structural perturbation of the native membrane by cleavage of the C-terminus decreases the number of ions per bR to 1.4. The observed ratio of total ions in this sample to total ions in bR is found to agree with that calculated using known binding constants for each. The results on the number of metal cations/bR and their ratio in bacterio-opsin agrees with the calculated number using previously observed binding constants in deionized bO (Yang; et al. Biophys J., in press) only if one assumes that the second high-affinity site (not the first) is removed by retinal removal. Removal of 75\% of the lipids from the purple membrane is found to greatly reduce the number of metal cations from 2 to 0.16. This suggest that if metal cations are in the two high-affinity sites (which are the only type of binding sites evident in our native bR sample), the removal of lipids, known to change the protein tertiary structure, changes also the metal ion binding sites.},
	isbn = {0022-3654},
	doi = {doi: 10.1021/jp952951i},
	url = {http://dx.doi.org/10.1021/jp952951i},
	author = {Griffiths, Jennifer A. and King, John and Yang, Difei and Browner, Richard and El-Sayed, Mostafa A}
}
@article {863,
	title = {Catalysis of the retinal subpicosecond photoisomerization process in acid purple bacteriorhodopsin and some bacteriorhodopsin mutants by chloride ions.},
	journal = {Biophysical journal},
	volume = {71},
	year = {1996},
	month = {1996 Sep},
	pages = {1545-53},
	abstract = {The dynamics and the spectra of the excited state of the retinal in bacteriorhodopsin (bR) and its K-intermediate at pH 0 was compared with that of bR and halorhodopsin at pH 6.5. The quantum yield of photoisomerization in acid purple bR was estimated to be at least 0.5. The change of pH from 6.5 to 2 causes a shift of the absorption maximum from 568 to 600 nm (acid blue bR) and decreases the rate of photoisomerization. A further decrease in pH from 2 to 0 shifts the absorption maximum back to 575 nm when HCl is used (acid purple bR). We found that the rate of photoisomerization increases when the pH decreases from 2 to 0. The effect of chloride anions on the dynamics of the retinal photoisomerization of acid bR (pH 2 and 0) and some mutants (D85N, D212N, and R82Q) was also studied. The addition of 1 M HCl (to make acid purple bR, pH 0) or 1 M NaCl to acid blue bR (pH 2) was found to catalyze the rate of the retinal photoisomerization process. Similarly, the addition of 1 M NaCl to the solution of some bR mutants that have a reduced rate of retinal photoisomerization (D85N, D212N, and R82Q) was found to catalyze the rate of their retinal photoisomerization process up to the value observed in wild-type bR. These results are explained by proposing that the bound Cl- compensates for the loss of the negative charges of the COO- groups of Asp85 and/or Asp212 either by neutralization at low pH or by residue replacement in D85N and D212N mutants.},
	keywords = {Acoustics, Anions, Bacteriorhodopsins, Biophysical Phenomena, Biophysics, Catalysis, Chlorides, Halobacterium salinarum, Hydrogen-Ion Concentration, Kinetics, Photochemistry, Point Mutation, Retinaldehyde, Spectrophotometry},
	issn = {0006-3495},
	doi = {10.1016/S0006-3495(96)79357-8},
	author = {Logunov, Stephan L. and El-Sayed, Mostafa A and Lanyi, Janos K.}
}
@article {877,
	title = {{\textquotedblleft}Cubic{\textquotedblright} Colloidal Platinum Nanoparticles},
	journal = {Chemistry of Materials},
	volume = {8},
	year = {1996},
	note = {doi: 10.1021/cm9601190},
	month = {1996},
	pages = {1161 - 1163},
	publisher = {American Chemical Society},
	abstract = {Cubic platinum nanoparticles (4-18 nm) have been synthesized for the first time in solution by the controlled reduction of K2PtCl4 with hydrogen gas in the presence of sodium polyacrylate as a capping material. The nanoparticles are found to have fee structures, similar to the bulk metal with {100} facets.},
	isbn = {0897-4756},
	doi = {10.1021/cm9601190},
	url = {http://dx.doi.org/10.1021/cm9601190},
	author = {Ahmadi, Temer S. and Wang, Z.L. and Henglein, A. and El-Sayed, Mostafa A}
}
@article {860,
	title = {The Ca2+ binding to deionized monomerized and to retinal removed bacteriorhodopsin.},
	journal = {Biophysical journal},
	volume = {69},
	year = {1995},
	month = {1995 Nov},
	pages = {2056-9},
	abstract = {In our continuing effort to characterize the metal cation binding in bacteriorhodopsin (bR) using Ca(2+)-specific electrodes, potentiometric titration was carried out on deionized solubilized bR (containing monomeric units) and deionized bacterioopsin (bR with its retinal removed). Scatchard plots were analyzed. The monomer was found to have plots similar to those of the trimer, suggesting that the binding sites in bR are localized within the protein monomer unit and not between the molecules within the trimer structure. This also supports the previous assumption that the curvature in the Scatchard plot of regenerated bR is not due to cooperativity of metal cation within the trimer, but rather due to multiple sites. Recent studies further support the finding that the curved Scatchard plot is not due to the cooperativity between the metal ions in the two high affinity sites, wherever they are. The results of the analysis of the Scatchard plot for deionized bacterioopsin have shown a change in the binding characteristics of the high affinity but not the low affinity sites from that observed in bR. This result supports previous conclusions that metal cations in the high affinity sites are not far from the retinal cavity.},
	keywords = {Bacteriorhodopsins, Binding Sites, Biophysical Phenomena, Biophysics, Calcium, Electrochemistry, Halobacterium, Ions, Kinetics, Protein Conformation, Retinaldehyde},
	issn = {0006-3495},
	doi = {10.1016/S0006-3495(95)80075-5},
	author = {Yang, Difei and El-Sayed, Mostafa A}
}
@article {1275,
	title = {Comparison between the Binding of Ca2+ and Mg2+ to the Two High-Affinity Sites of Bacteriorhodopsin},
	journal = {The Journal of Physical Chemistry},
	volume = {99},
	year = {1995},
	note = {doi: 10.1021/j100029a043},
	month = {1995},
	pages = {11600 - 11604},
	publisher = {American Chemical Society},
	abstract = {See http://dx.doi.org/10.1021/j100029a043 for article{\textquoteright}s front page in lieu of an abstract },
	isbn = {0022-3654},
	doi = {doi: 10.1021/j100029a043},
	url = {http://dx.doi.org/10.1021/j100029a043},
	author = {Yoo, Seoung-Kyo and Awad, Elias S. and El-Sayed, Mostafa A}
}
