@article {1649,
	title = {Operando Investigation into Dynamic Evolution of Cathode{\textendash}Electrolyte Interfaces in a Li-Ion Battery},
	journal = {Nano letters},
	year = {2019},
	author = {Chen, D. and Mahmoud, M.A. and Wang, J.H. and Waller, G.H. and Zhao, B. and Qu, C. and El-Sayed, M.A. and Liu, M.}
}
@article {1636,
	title = {Dual-excitation nanocellulose-plasmonic membranes for molecular and cellular SERS detection},
	journal = {ACS applied materials \& interfaces},
	year = {2018},
	author = {S. Zhang and R. Xiong and Mahmoud, M A and E. Quigley and H. Chang and El-Sayed, M. A. and Tsukruk, V. V.}
}
@article {1329,
	title = {Antiandrogen Gold Nanoparticles Dual-Target and Overcome Treatment Resistance in Hormone-Insensitive Prostate Cancer Cells},
	journal = {Bioconjugate Chemistry},
	volume = {23},
	number = {8},
	year = {2012},
	note = {Times Cited: 0Dreaden, Erik C. Gryder, Berkley E. Austin, Lauren A. Defo, Brice A. Tene Hayden, Steven C. Pi, Min Quarles, L. Darryl Oyelere, Adegboyega K. El-Sayed, Mostafa A.},
	month = {Aug},
	pages = {1507-1512},
	abstract = {prostate cancer is the most commonly diagnosed cancer among men in the developed countries.(1) One in six males in the U.S.(2) and one in nine males in the U.K.(3) will develop the disease at some point during their lifetime. Despite advances in prostate cancer screening, more than a quarter of a million men die from the disease every year(1) due primarily to treatment-resistance and metastasis. Colloidal nanotechnologies can provide tremendous enhancements to existing targeting/treatment strategies for prostate cancer to which malignant cells are less sensitive. Here, we show that antiandrogen gold nanoparticles-multivalent analogues of antiandrogens currently used in clinical therapy for prostate cancer-selectively engage two distinct receptors, androgen receptor (AR), a target for the treatment of prostate cancer, as well as a novel G-protein coupled receptor, GPRC6A, that is also upregulated in prostate cancer. These nanoparticles selectively accumulated in hormone-insensitive and chemotherapy resistant prostate cancer cells, bound androgen receptor with multivalent affinity, and exhibited greatly enhanced drug potency versus monovalent antiandrogens currently in clinical use Further, antiandrogen gold nanoparticles selectively stimulated GPRC6A with multivalent affinity, demonstrating that the delivery of nanoscale antiandrogens can also be facilitated by the transmembrane receptor in order to realize increasingly selective, increasingly potent therapy for treatment-resistant prostate cancers.},
	isbn = {1043-1802},
	doi = {10.1021/bc300158k},
	author = {Dreaden, E. C. and Gryder, B. E. and Austin, Lauren and Defo, B. A. T. and Hayden, S. C. and Pi, M. and Quarles, L. D. and Oyelere, A. K. and El-Sayed, M. A.}
}
@article {1343,
	title = {Photoelectric Conversion Properties of Dye-Sensitized Solar Cells Using Dye-Dispersing Titania},
	journal = {Journal of Physical Chemistry C},
	volume = {116},
	number = {7},
	year = {2012},
	note = {Times Cited: 1Nishikiori, Hiromasa Uesugi, Yohei Setiawan, Rudi Agus Fujii, Tsuneo Qian, Wei El-Sayed, Mostafa A.},
	month = {Feb},
	pages = {4848-4854},
	abstract = {The time-resolved fluorescence and photoelectrochemical properties of dye-sensitized solar cells using crystalline titania electrodes coated with N3 dye-dispersing amorphous titania gel were investigated to clarify the influence of the dye titania interaction and electron transfer on their photoelectric conversion performance. The photocurrent quantum efficiency of the electrodes was remarkably increased by a steam treatment due to the crystallization and densification of the amorphous titania layer compared to that of the untreated electrode. The electron injection from the dye to the crystalline titania foundation via the steam-treated titania dispersing the dye was confirmed to be more efficient than that in the conventional electrodes. The dye-dispersing titania layer prevented interaction between the dye molecules and back electron transfer from the titania to the electrolyte. The charge separation and photoelectric conversion performance of the dye-sensitized solar cells were improved by forming the specific dye-dispersing titania layer.},
	isbn = {1932-7447},
	doi = {10.1021/jp2094388},
	author = {Nishikiori, H. and Uesugi, Y. and Setiawan, R. A. and Fujii, T. and Qian, W. and El-Sayed, M. A.}
}
@article {1076,
	title = {Following Charge Separation on the Nanoscale in Cu(2)O-Au Nanoframe Hollow Nanoparticles},
	journal = {Nano Letters},
	volume = {11},
	number = {8},
	year = {2011},
	note = {A. Mahmoud, Mahmoud Qian, Wei El-Sayed, Mostafa A.},
	month = {Aug},
	pages = {3285-3289},
	abstract = {Cu(2)O-Au nanoframes with different nanolayer thicknesses of Cu(2)O were prepared, and their photocatalytic properties in aqueous solutions were studied. Cu(2)O semiconductor excitation leads to electron-hole separation. In aqueous solution, the hole is known to oxidize water to produce hydroxyl radicals whose concentration (and that of the holes) can be monitored by the rate of the degradation of dissolved methylene blue dye. The exciton lifetime is determined by femtosecond techniques and is determined by electron-hole recombination which depends on the rates of a number of competing processes such as, electron or hole transfer to an acceptor such as a gold nanoframe and/or the electron or hole trapping processes at the Cu(2)O-Au nanoframe interface. We measured the exciton lifetime as a function of the average Cu(2)O-Au layer separation. A good correlation was found between the rate of the photocatalytic degradation of methylene blue and the exciton lifetime. The exciton lifetime is found to increase as the Cu(2)O thickness is increased. This leads to an increase in the electron-hole separation time and thus an increase in the hole (and so the hydroxyl radical) concentration leading to an observed enhanced rate of the dye degradation.},
	isbn = {1530-6984},
	doi = {10.1021/nl201642r},
	author = {Mahmoud, M A and Qian, Wei and El-Sayed, Mostafa A}
}
@article {1075,
	title = {Influence of Steam Treatment on Dye-Titania Complex Formation and Photoelectric Conversion Property of Dye-Doped Titania Gel},
	journal = {Journal of Physical Chemistry C},
	volume = {115},
	number = {6},
	year = {2011},
	note = {Nishikiori, Hiromasa Uesugi, Yohei Takami, Shohei Setiawan, RudiAgus Fujii, Tsuneo Qian, Wei El-Sayed, Mostafa A.},
	month = {Feb},
	pages = {2880-2887},
	abstract = {Xanthene dye molecules form a chelate complex with the titanium species on the titania surface in dye-titania systems. The complex formation causes a fast electron injection into the titania conduction band. In this study, simple spectroscopic and photocurrent measurements of the xanthene dye-doped titania gels prepared by the sol-gel method were conducted in order to clarify the influence of a steam treatment on the dye-titania interaction and electron transfer. The photocurrent quantum efficiency of the fluorescein-doped electrode was remarkably increased by the steam treatment compared to that of the untreated electrode consisting of an amorphous titania gel. The photocurrent action spectrum was red-shifted, and the short circuit photocurrent and open circuit voltage values increased with the steam treatment time. The steam treatment promoted the dye-titania complex formation, a negative shift in the conduction band potential of the titania, and the electron injection from the dye to the titania.},
	isbn = {1932-7447},
	doi = {10.1021/jp109958z},
	author = {Nishikiori, H. and Uesugi, Y. and Takami, S. and Setiawan, R. and Fujii, T. and Qian, Wei and El-Sayed, Mostafa A}
}
@article {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 {1097,
	title = {Comparative study of photothermolysis of cancer cells with nuclear-targeted or cytoplasm-targeted gold nanospheres: continuous wave or pulsed lasers},
	journal = {Journal of Biomedical Optics},
	volume = {15},
	number = {5},
	year = {2010},
	note = {Huang, Xiaohua Kang, Bin Qian, Wei Mackey, Megan A. Chen, Po C. Oyelere, Adegboyega K. El-Sayed, Ivan H. El-Sayed, Mostafa A.},
	month = {Sep-Oct},
	abstract = {We conduct a comparative study on the efficiency and cell death pathways of continuous wave (cw) and nanosecond pulsed laser photothermal cancer therapy using gold nanospheres delivered to either the cytoplasm or nucleus of cancer cells. Cytoplasm localization is achieved using arginine-glycine-aspartate peptide modified gold nanospheres, which target integrin receptors on the cell surface and are subsequently internalized by the cells. Nuclear delivery is achieved by conjugating the gold nanospheres with nuclear localization sequence peptides originating from the simian virus. Photothermal experiments show that cell death can be induced with a single pulse of a nanosecond laser more efficiently than with a cw laser. When the cw laser is applied, gold nanospheres localized in the cytoplasm are more effective in inducing cell destruction than gold nanospheres localized at the nucleus. The opposite effect is observed when the nanosecond pulsed laser is used, suggesting that plasmonic field enhancement of the nonlinear absorption processes occurs at high localization of gold nanospheres at the nucleus. Cell death pathways are further investigated via a standard apoptosis kit to show that the cell death mechanisms depend on the type of laser used. While the cw laser induces cell death via apoptosis, the nanosecond pulsed laser leads to cell necrosis. These studies add mechanistic insight to gold nanoparticle-based photothermal therapy of cancer. (c) 2010 Society of Photo-Optical Instrumentation Engineers. [DOI: 10.1117/1.3486538]},
	isbn = {1083-3668},
	doi = {10.1117/1.3486538},
	author = {Huang, Xiaohua and Kang, Bin and Qian, Wei and Mackey, M. A. and Chen, P. C. and Oyelere, A. K. and El Sayed, I.H. and El-Sayed, Mostafa A}
}
@article {810,
	title = {Dark-field light scattering imaging of living cancer cell component from birth through division using bioconjugated gold nanoprobes},
	journal = {Journal of Biomedical Optics},
	volume = {15},
	year = {2010},
	pages = {046025},
	abstract = {Novel methods and technologies that could extend and complement the capabilities of the prevailing fluorescence microscope in following the cell cycle under different perturbations are highly desirable in the area of biological and biomedical imaging. We report a newly designed instrument for long-term light scattering live cell imaging based on integrating a homebuilt environmental cell incubation minichamber and an angled dark-field illumination system into a conventional inverted light microscope. Peptide-conjugated gold nanoparticles that are selectively delivered to either the cytoplasmic or nuclear region of the cell are used as light scattering contrast agents. The new system enables us to carry out continuous and intermittence-free dark-field live cell imaging over several tens of hours. A variety of applications of this imaging system are demonstrated, such as monitoring the nuclear uptake of peptide-conjugated gold nanoparticles, tracking the full cycle of cancer cells from birth to division, following the chromosome dynamics during cell mitosis, and observing the intracellular distribution of gold nanoparticles after cell division. We also discuss the overall effect of nuclear targeting gold nanoparticles on the cell viability of parent and daughter cells.},
	doi = {10.1117/1.3477179},
	url = {http://dx.doi.org/10.1117/1.3477179},
	author = {Qian, Wei and Huang, Xiaohua and Kang, Bin and El-Sayed, Mostafa A}
}
@article {1104,
	title = {Delivery of molecules into cells using carbon nanoparticles activated by femtosecond laser pulses},
	journal = {Nature Nanotechnology},
	volume = {5},
	number = {8},
	year = {2010},
	note = {Chakravarty, Prerona Qian, Wei El-Sayed, Mostafa A. Prausnitz, Mark R.},
	month = {Aug},
	pages = {607-611},
	abstract = {A major barrier to drug and gene delivery is crossing the cell{\textquoteright}s plasma membrane. Physical forces applied to cells via electroporation(1), ultrasound(2) and laser irradiation(3-6) generate nanoscale holes in the plasma membrane for direct delivery of drugs into the cytoplasm. Inspired by previous work showing that laser excitation of carbon nanoparticles can drive the carbon-steam reaction to generate highly controlled shock waves(7-10), we show that carbon black nanoparticles activated by femtosecond laser pulses can facilitate the delivery of small molecules, proteins and DNA into two types of cells. Our initial results suggest that interaction between the laser energy and carbon black nanoparticles may generate photo-acoustic forces by chemical reaction to create transient holes in the membrane for intracellular delivery.},
	isbn = {1748-3387},
	doi = {10.1038/nnano.2010.126},
	author = {Chakravarty, P. and Qian, Wei and El-Sayed, Mostafa A and Prausnitz, M. R.}
}
@article {1114,
	title = {The Dependence of the Plasmon Field Induced Nonradiative Electronic Relaxation Mechanisms on the Gold Shell Thickness in Vertically Aligned CdTe-Au Core-Shell Nanorods},
	journal = {Nano Letters},
	volume = {9},
	number = {11},
	year = {2009},
	note = {Neretina, Svetlana Dreaden, Erik C. Qian, Wei El-Sayed, Mostafa A. Hughes, Robert A. Preston, John S. Mascher, Peter},
	month = {Nov},
	pages = {3772-3779},
	abstract = {The dependence of the plasmon field enhancement of the nonradiative relaxation rate of the band gap electrons in vertically aligned CdTe-Au core-shell nanorods on the plasmonic gold nanoshell thickness is examined. Increasing the thickness of the gold nanoshell from 15 to 26 nm is found to change the decay curve from being nonexponential and anisotropic to one that is fully exponential and isotropic (i.e., independent of the nanorod orientation with respect to the exciting light polarization direction). Analysis of the kinetics of the possible electronic relaxation enhancement mechanisms is carried out, and DDA simulated properties of the induced plasmonic field of the thin and thick gold nanoshells are determined. On the basis of the conclusions of these treatments and the experimental results, it is concluded that by increasing the nanoshell thickness the relaxation processes evolve from multiple enhancement mechanisms, dominated by highly anisotropic Auger processes, to mechanism(s) involving first-order excited electron ejection process(es). The former is shown to give rise to nonexponential anisotropic decays in the dipolar plasmon field of the thin nanoshell, while the latter exhibits an exponential isotropic decay in the unpolarized plasmonic field of the thick nanoshell.},
	isbn = {1530-6984},
	doi = {10.1021/nl901960w},
	author = {Neretina, Svetlana and Dreaden, Erik and Qian, Wei and El-Sayed, Mostafa A and Hughes, Robert A and Preston, John S and Mascher, Peter}
}
@article {1113,
	title = {Exciton Lifetime Tuning by Changing the Plasmon Field Orientation with Respect to the Exciton Transition Moment Direction: CdTe-Au Core-Shell Nanorods},
	journal = {Nano Letters},
	volume = {9},
	number = {3},
	year = {2009},
	note = {Neretina, Svetlana Qian, Wei Dreaden, Erik C. El-Sayed, Mostafa A. Hughes, Robert A. Preston, John S. Mascher, Peter},
	month = {Mar},
	pages = {1242-1248},
	abstract = {We studied the anisotropy of the influence of plasmonic fields, arising from the optical excitation of a gold nanoshell plasmon absorption at 770 nm, on the lifetime of the bandgap state of the CdTe core in vertically aligned CdTe-Au core-shell nanorods. The previously observed decrease in the lifetime was studied as a function of the tilt angle between the long axis of the nanorod and the electric field polarization direction of the plasmon inducing exciting light. It is observed that the strongest enhancement to the exciton relaxation rate occurs when the two axes are parallel to one another. These results are discussed in terms of the coupling between the exciton transition moment of the CdTe rod and the electric field polarization direction of the gold nanoshell plasmon at 770 nm, which was determined from theoretical modeling based on the discrete dipole approximation.},
	isbn = {1530-6984},
	doi = {10.1021/nl900183m},
	author = {Neretina, Svetlana and Qian, Wei and Dreaden, Erik and El-Sayed, Mostafa A and Hughes, Robert A and Preston, John S and Mascher, Peter}
}
@article {1119,
	title = {Gold Nanoparticles Surface Plasmon Field Effects on the Proton Pump Process of the Bacteriorhodopsin Photosynthesis},
	journal = {Journal of the American Chemical Society},
	volume = {131},
	number = {7},
	year = {2009},
	note = {Biesso, Arianna Qian, Wei Huang, Xiaohua El-Sayed, Mostafa A.},
	month = {Feb},
	pages = {2442-+},
	abstract = {The rate of the proton pump of bacteriorhodopsin photosynthetic system is examined in the presence of a gold nanorod plasmon field. It is found that while the rate of the proton dissociation from the protonated Schiff base is not affected, the rate of its reprotonation increases. These results are qualitatively discussed in terms of several possible mechanisms.},
	isbn = {0002-7863},
	doi = {10.1021/ja8088873},
	author = {Biesso, A. and Qian, Wei and Huang, Xiaohua and El-Sayed, Mostafa A}
}
@article {1128,
	title = {Gigahertz optical modulation resulting from coherent lattice oscillations induced by femtosecond laser pumping of 2D photonic crystals of gold-capped polystyrene microspheres},
	journal = {Advanced Materials},
	volume = {20},
	number = {4},
	year = {2008},
	note = {Huang, Wenyu Qian, Wei El-Sayed, Mostafa A.},
	month = {Feb},
	pages = {733-+},
	abstract = {A gigahertz all-optical modulation technique, based on a mechanism in which the modulation of the transmitted light is caused by the coherent oscillation of the phonon modes of gold caps on periodic polystyrene sphere monolayer arrays, is demonstrated. The modulation frequency can be tuned by changing the size of the polystyrene spheres.},
	isbn = {0935-9648},
	doi = {10.1002/adma.200701543},
	author = {Huang, Wenyu and Qian, Wei and El-Sayed, Mostafa A}
}
@article {1133,
	title = {Gold nanoparticle plasmonic field effect on the primary step of the other photosynthetic system in nature, bacteriorhodopsin},
	journal = {Journal of the American Chemical Society},
	volume = {130},
	number = {11},
	year = {2008},
	note = {Biesso, Arianna Qian, Wei El-Sayed, Mostafa A.},
	month = {Mar},
	pages = {3258-+},
	abstract = {In regards to the effect of the surface plasmon field of gold nanospheres on the rate of primary steps leading to retinal photoisomerization in the photosynthesis of bacterirhodopsin (bR), 4 is believed that the light absorption of bR that leads to its retinal isomerization first involves the formation of a highly polar electronic excited state (1460) of the all-trans isomer which strongly polarizes the protein around it. This is followed by its decay to a viibrationally excited 13-cis isomer (J(625)). The effect of plasmonic field of gold nanospheres of different sizes and concentrations is found to slow down the rate of the isomerization of the polar electronic excited-state to the J625 but has no effect on the vibration relaxation of the isomeric state itself. This is consistent with the electrostatic nature of the plasmonic field.},
	isbn = {0002-7863},
	doi = {10.1021/ja7099858},
	author = {Biesso, A. and Qian, Wei and El-Sayed, Mostafa A}
}
@article {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 {1141,
	title = {Cancer cells assemble and align gold nanorods conjugated to antibodies to produce highly enhanced, sharp, and polarized surface Raman spectra: A potential cancer diagnostic marker},
	journal = {Nano Letters},
	volume = {7},
	number = {6},
	year = {2007},
	note = {Huang, Xiaohua El-Sayed, Ivan H. Qian, Wei El-Sayed, Mostafa A.},
	month = {Jun},
	pages = {1591-1597},
	abstract = {Human oral cancer cells are found to assemble and align gold nanorods conjugated to anti-epidermal growth factor receptor (anti-EGFR) antibodies. Immnoconjugated gold nanorods and nanospheres were shown previously to exhibit strong Rayleigh (Mie) scattering useful for imaging. In the present letter, molecules near the nanorods on the cancer cells are found to give a Raman spectrum that is greatly enhanced (due to the high surface plasmon field of the nanorod assembly in which their extended surface plasmon fields overlap), sharp (due to a homogeneous environment), and polarized (due to anisotropic alignments). These observed properties can be used as diagnostic signatures for cancer cells.},
	isbn = {1530-6984},
	doi = {10.1021/nl070472c},
	author = {Huang, Xiaohua and El Sayed, I.H. and Qian, Wei and El-Sayed, Mostafa A}
}
@article {1136,
	title = {Change in titania structure from amorphousness to crystalline increasing photoinduced electron-transfer rate in dye-titania system},
	journal = {Journal of Physical Chemistry C},
	volume = {111},
	number = {26},
	year = {2007},
	note = {Nishikiori, Hiromasa Qian, Wei El-Sayed, Mostafa A. Tanaka, Nobuaki Fujii, Tsuneo},
	month = {Jul},
	pages = {9008-9011},
	abstract = {Thin titania gel films containing well-dispersed fluorescein dye were prepared by the sol-gel method and treated with steam to promote crystal growth of the titania particles. It is known that steam treatment converts the titania structure from amorphousness to crystalline. In the present study, such change is found to increase the rate of the photoinduced electron transfer from and to dispersed fluorescein dye molecules.},
	isbn = {1932-7447},
	doi = {10.1021/jp072625q},
	author = {Nishikiori, H. and Qian, Wei and El-Sayed, Mostafa A and Tanaka, N. and Fujii, T.}
}
@article {1134,
	title = {Dependence of the threshold energy of femtosecond laser ejection of gold nanoprisms from quartz substrates on the nanoparticle environment},
	journal = {Journal of Physical Chemistry C},
	volume = {111},
	number = {25},
	year = {2007},
	note = {Tabor, Christopher Qian, Wei El-Sayed, Mostafa A.},
	month = {Jun},
	pages = {8934-8941},
	abstract = {Recently, it was reported that gold nanoprisms in a monolayer array on a quartz substrate were ejected in air when irradiated with femtosecond laser pulses near their surface plasmon absorption maximum. It was deduced from the measured reduction in particle thickness upon irradiation that the ejection mechanism involved ablation of surface atoms from the gold particle, which generates an intense pressure at the particle-substrate interface. The present study reports on this phenomenon when the substrate-bound nanoparticle is immersed in a liquid environment. In this system, it is found that the nanoparticle ejection requires less than one tenth the energy required if the system was irradiated in air. The ejected nanoparticle is also found to increase in thickness instead of the decrease observed in air. These results suggest another photoinitiated ejection mechanism, different from surface ablation, when the particles are surrounded by a liquid environment. From this and other spectroscopic and microscopic results on the ejected nanoprisms, we suggest a mechanism that involves energy transfer from the photoexcited nanoprism to the solvent within cavities and defects at the particle-substrate interface. The hot-solvent molecules result in an intense pressure at the particle-substrate interface, resulting in particle ejection. Ejection is proposed to consist of two processes, namely nanoparticle-substrate dissociation and nanoparticle solvation and diffusion away from the substrate. These two processes have independently been studied as a function of solvent property.},
	isbn = {1932-7447},
	doi = {10.1021/jp070282q},
	author = {Tabor, C. E. and Qian, Wei and El-Sayed, Mostafa A}
}
@article {1143,
	title = {The effect of plasmon field on the coherent lattice phonon oscillation in electron-beam fabricated gold nanoparticle pairs},
	journal = {Nano Letters},
	volume = {7},
	number = {10},
	year = {2007},
	note = {Huang, Wenyu Qian, Wei Jain, Prashant K. El-Sayed, Mostafa A.},
	month = {Oct},
	pages = {3227-3234},
	abstract = {By using electron beam lithography, we fabricated pairs of gold nanoparticles with varying interparticle separation. Double-beam femtosecond transient absorption spectroscopy was used to determine the coherent lattice oscillation frequency as a function of the interparticle separation in the presence of the plasmon field excited by the monitoring probe light. We found that the fractional shift in the coherent lattice phonon oscillation frequency follows an exponential decay with respect to the interparticle gap scaled by the disc diameter with the same decay constant as that previously observed for the fractional shift in the surface plasmon electronic oscillation resonance frequency. This strongly suggests that it is the near-field coupling between the particles that shifts both the coherent electronic oscillation (plasmon) frequency and the coherent lattice oscillation (phonon) frequency. The similar trend in the effect of interparticle coupling on the plasmon frequency and the phonon frequency is essentially a reflection of the universal scaling behavior of the distance decay of the interparticle plasmonic near-field. It is shown that the observed decrease in the lattice oscillation frequency with decrease in the interparticle distance is the result of a reduction in the effective free electron density within each nanoparticle pair partner as a result of the polarizing perturbation of the plasmonic field of the other nanoparticle in the pair.},
	isbn = {1530-6984},
	doi = {10.1021/nl071813p},
	author = {Huang, Wenyu and Qian, Wei and Jain, Prashant K and El-Sayed, Mostafa A}
}
@article {1144,
	title = {Effect of the lattice crystallinity on the electron-phonon relaxation rates in gold nanoparticles},
	journal = {Journal of Physical Chemistry C},
	volume = {111},
	number = {29},
	year = {2007},
	note = {Huang, Wenyu Qian, Wei El-Sayed, Mostafa A. Ding, Yong Wang, Zhong Lin},
	month = {Jul},
	pages = {10751-10757},
	abstract = {In order to study the importance of surface phonons on the electron-phonon relaxation in plasmonic nanoparticles, the effect of size, shape, and materials have recently been studied. Gold and silver nanoparticles have shown no dependence on size and shape while copper nanoparticles have shown some size dependence. This suggests that the bulk phonons, which are sensitive to the bulk-phase structure, are solely responsible for the relaxation of the hot electron in gold and silver plasmonic nanoparticles. The importance of bulk phonons should depend on the degree of crystallinity. In the present study, we have found that the electron-phonon relaxation rate decreases greatly when polycrystalline prismatic gold nanoparticles are annealed and transformed into nearly single-crystalline nanospheres. The results are explained by the presence of high-density grain boundaries with dense, high-frequency molecular type vibrations which are effective in removing the energy of the excited electrons in the polycrystalline prismatic nanoparticles.},
	isbn = {1932-7447},
	doi = {10.1021/jp0738917},
	author = {Huang, Wenyu and Qian, Wei and El-Sayed, Mostafa A and Ding, Y. and Wang, Z.L.}
}
@article {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 {1153,
	title = {Cancer cell imaging and photothermal therapy in the near-infrared region by using gold nanorods},
	journal = {Journal of the American Chemical Society},
	volume = {128},
	number = {6},
	year = {2006},
	note = {Huang, XH El-Sayed, IH Qian, W El-Sayed, MA},
	month = {Feb},
	pages = {2115-2120},
	abstract = {Due to strong electric fields at the surface, the absorption and scattering of electromagnetic radiation by noble metal nanoparticles are strongly enhanced. These unique properties provide the potential of designing novel optically active reagents for simultaneous molecular imaging and photothermal cancer therapy. It is desirable to use agents that are active in the near-infrared (NIR) region of the radiation spectrum to minimize the light extinction by intrinsic chromophores in native tissue. Gold nanorods with suitable aspect ratios (length divided by width) can absorb and scatter strongly in the NIR region (650-900 nm). In the present work, we provide an in vitro demonstration of gold nanorods as novel contrast agents for both molecular imaging and photothermal cancer therapy. Nanorods are synthesized and conjugated to anti-epidermal growth factor receptor (anti-EGFR) monoclonal antibodies and incubated in cell cultures with a nonmalignant epithelial cell line (HaCat) and two malignant oral epithelial cell lines (HOC 313 clone 8 and HSC 3). The anti-EGFR anti body-conjugated nanorods bind specifically to the surface of the malignant-type cells with a much higher affinity due to the overexpressed EGFR on the cytoplasmic membrane of the malignant cells. As a result of the strongly scattered red light from gold nanorods in dark field, observed using a laboratory microscope, the malignant cells are clearly visualized and diagnosed from the nonmalignant cells. It is found that, after exposure to continuous red laser at 800 nm, malignant cells require about half the laser energy to be photothermally destroyed than the nonmalignant cells. Thus, both efficient cancer cell diagnostics and selective photothermal therapy are realized at the same time.},
	keywords = {display},
	isbn = {0002-7863},
	doi = {10.1021/ja057254a},
	author = {Huang, Xiaohua and El Sayed, I.H. and Qian, Wei and El-Sayed, Mostafa A.}
}
@article {1154,
	title = {Gold nanoparticles propulsion from surface fueled by absorption of femtosecond laser pulse at their surface plasmon resonance},
	journal = {Journal of the American Chemical Society},
	volume = {128},
	number = {41},
	year = {2006},
	note = {Huang, Wenyu Qian, Wei El-Sayed, Mostafa A.},
	month = {Oct},
	pages = {13330-13331},
	isbn = {0002-7863},
	doi = {10.1021/ja064328p},
	author = {Huang, Wenyu and Qian, Wei and El-Sayed, Mostafa A}
}
@article {1160,
	title = {Observation of optical gain in solutions of CdS quantum dots at room temperature in the blue region},
	journal = {Applied Physics Letters},
	volume = {88},
	number = {26},
	year = {2006},
	note = {Darugar, Q Qian, W El-Sayed, MA},
	month = {Jun},
	abstract = {The optical gain dynamics has been studied for two CdS quantum dot samples dispersed in toluene at room temperature. This was carried out by using femtosecond transient absorption technique with an excitation at 400 nm and gain measurement was studied at the fluorescence maxima (440 and 460 nm). The optical gain lifetime was found to be as long as 20 ps under pump fluence as low as 0.77 mJ/cm(2). The low threshold is the result of long lifetime of electrons and holes and narrow emission bandwidth. These results suggest that CdS quantum dots in solution are excellent gain media for optically pumped high power blue lasers.},
	isbn = {0003-6951},
	doi = {10.1063/1.2217138},
	author = {Darugar, Q. and Qian, Wei and El-Sayed, Mostafa A}
}
@article {1159,
	title = {Size-dependent ultrafast electronic energy relaxation and enhanced fluorescence of copper nanoparticles},
	journal = {Journal of Physical Chemistry B},
	volume = {110},
	number = {1},
	year = {2006},
	note = {Darugar, Q Qian, W El-Sayed, MA Pileni, MP},
	month = {Jan},
	pages = {143-149},
	abstract = {The energy relaxation of the electrons in the conduction band of 12 and 30 nm diameter copper nanoparticles in colloidal solution was investigated using femtosecond time-resolved transient spectroscopy. Experimental results show that the hot electron energy relaxation is faster in 12 nm copper nanoparticles (0.37 ps) than that in 30 nm copper nanoparticles (0.51 ps), which is explained by the size-dependent electron-surface phonon coupling. Additional mechanisms involving trapping or energy transfer processes to the denser surface states (imperfection) in the smaller nanoparticles are needed to explain the relaxation rate in the 12 nm nanoparticles. The observed fluorescence quantum yield from these nanoparticles is found to be enhanced by roughly 5 orders of magnitude for the 30 nm nanoparticles and 4 orders of magnitude for the 12 nm nanoparticles (relative to bulk copper metal). The increase in the fluorescence quantum yield is attributed to the electromagnetic enhancement of the radiative recombination of the electrons in the s-p conduction band below the Fermi level with the holes in the d bands due to the strong surface plasmon oscillation in these nanoparticles.},
	isbn = {1520-6106},
	doi = {10.1021/jp0545445},
	author = {Darugar, Q. and Qian, Wei and El-Sayed, Mostafa A and Pileni, Marie-Paule}
}
@article {1148,
	title = {Ultrafast cooling of photoexcited electrons in gold nanoparticle-thiolated DNA conjugates involves the dissociation of the gold-thiol bond},
	journal = {Journal of the American Chemical Society},
	volume = {128},
	number = {7},
	year = {2006},
	note = {Jain, PK Qian, W El-Sayed, MA},
	month = {Feb},
	pages = {2426-2433},
	abstract = {Using UV-visible extinction spectroscopy and femtosecond pump-probe transient absorption spectroscopy, we have studied the effect of femtosecond laser heating on gold nanoparticles attached to DNA ligands via thiol groups. It is found that femtosecond pulse excitation of the DNA-modified nanoparticles at a wavelength of 400 nm leads to desorption of the thiolated DNA strands from the nanoparticle surface by the dissociation of the gold-sulfur bond. The laser-initiated gold-sulfur bond-breaking process is a new pathway for nonradiative relaxation of the optically excited electrons within the DNA-modified gold nanoparticles, as manifested by a faster decay rate of the excited electronic distribution at progressively higher laser pulse energies. The experimental results favor a bond dissociation mechanism involving the coupling between the photoexcited electrons of the nanoparticles and the gold-sulfur bond vibrations over one involving the conventional phonon-phonon thermal heating processes. The latter processes have been observed previously by our group to be effective in the selective photothermal destruction of cancer cells bound to anti-epidermal growth factor receptor-conjugated gold nanoparticles.},
	isbn = {0002-7863},
	doi = {10.1021/ja056769z},
	author = {Jain, Prashant K and Qian, Wei and El-Sayed, Mostafa A}
}
@article {1149,
	title = {Ultrafast electron relaxation dynamics in coupled metal nanoparticles in aggregates},
	journal = {Journal of Physical Chemistry B},
	volume = {110},
	number = {1},
	year = {2006},
	note = {Jain, PK Qian, W El-Sayed, MA},
	month = {Jan},
	pages = {136-142},
	abstract = {We report the effect of aggregation in gold nanoparticles on their ultrafast electron-phonon relaxation dynamics measured by femtosecond transient absorption pump-probe spectroscopy. UV-visible extinction and transient absorption of the solution-stable aggregates of gold nanoparticles show a broad absorption in the 550-700-nm region in addition to the isolated gold nanoparticle plasmon resonance. This broad red-shifted absorption can be attributed to contributions from gold nanoparticle aggregates with different sizes and/or different fractal structures. The electron-phonon relaxation, reflected as a fast decay component of the transient bleach, is found to depend on the probe wavelength, suggesting that each wavelength interrogates one particular subset of the aggregates. As the probe wavelength is changed from 520 to 635 nm across the broad aggregate absorption, the rate of electron-phonon relaxation increases. The observed trend in the hot electron lifetimes can be explained on the basis of an increased overlap of the electron oscillation frequency with the phonon spectrum and enhanced interfacial electron scattering, with increasing extent of aggregation. The experimental results strongly suggest the presence of intercolloid electronic coupling within the nanoparticle aggregates, besides the well-known dipolar plasmon coupling.},
	isbn = {1520-6106},
	doi = {10.1021/jp055562p},
	author = {Jain, Prashant K and Qian, Wei and El-Sayed, Mostafa A}
}
@article {1146,
	title = {Ultrafast electronic relaxation and charge-carrier localization in CdS/CdSe/CdS quantum-dot quantum-well heterostructures},
	journal = {Nano Letters},
	volume = {6},
	number = {9},
	year = {2006},
	note = {Schill, Alexander W. Gaddis, Christopher S. Qian, Wei El-Sayed, Mostafa A. Cai, Ye Milam, Valeria T. Sandhage, Kenneth},
	month = {Sep},
	pages = {1940-1949},
	abstract = {The relaxation and localization times of excited electrons in CdS/CdSe/CdS colloidal quantum wells were measured using subpicosecond spectroscopy. HRTEM analysis and steady-state PL demonstrate a narrow size distribution of 5-6 nm epitaxial crystallites. By monitoring the rise time of the stimulated emission as a function of pump intensity, the relaxation times of the electron from the CdS core into the CdSe well are determined and assigned. Two-component rise times in the stimulated emission are attributed to intraband relaxation of carriers generated directly within the CdSe well ( fast component) and charge transfer of core-localized carriers across the CdS/CdSe interface ( slow component). This is the first reported observation of simultaneous photon absorption in the core and well of a quantum-dot heterostructure. With increasing pump intensity, the charge-transfer channel between the CdS core CdSe well contributes less to the stimulated emission signal because of filling and saturation of the CdSe well state, making the interfacial charge-transfer component less efficient. The interfacial charge-transfer time of the excited electron was determined from the slow component of the stimulated emission build-up time and is found to have a value of 1.2 ps.},
	isbn = {1530-6984},
	doi = {10.1021/nl061054v},
	author = {Schill, A. W. and Gaddis, C. S. and Qian, Wei and El-Sayed, Mostafa A and Cai, Y. and Milam, V. T. and Sandhage, K.}
}
@article {821,
	title = {The Optically Detected Coherent Lattice Oscillations in Silver and Gold Monolayer Periodic Nanoprism Arrays:  The Effect of Interparticle Coupling},
	journal = {The Journal of Physical Chemistry B},
	volume = {109},
	year = {2005},
	note = {doi: 10.1021/jp0526647},
	month = {2005},
	pages = {18881 - 18888},
	publisher = {American Chemical Society},
	abstract = {Using femtosecond transient spectroscopy, we studied the optically detected laser-induced coherent phonon oscillation of monolayers of periodic arrays of prismatic-shaped silver and gold nanoparticles, assembled by using the technique of nanosphere lithography. In this method, the same size of polystyrene sphere and the same vacuum conditions are used. Under these circumstances, the gold nanoprisms formed are found to have sharper tips than the corresponding silver nanoprisms. For both gold and silver nanoparticles, the surface plasmon absorption maximum is found to depend linearly on size. The coherent lattice oscillation periods are also found to depend linearly on size. However, although the observed dependence for the silver nanoparticle is found to follow the calculated dependence of a single particle on size (based on a one-dimensional standing wave model), the gold nanoparticle deviates from this model, and the deviation is found to increase with the size of the nanoparticles. This deviation can be explained by considering interparticle coupling. A simple interparticle lattice oscillating dipolar coupling model of the dimer is found to qualitatively account for both the sign and the size dependence of the deviation. The absence of this deviation in the silver nanoparticle arrays is blamed on the weak interparticle coupling due to their rounded tips and the possibility of oxidation of their surfaces.Using femtosecond transient spectroscopy, we studied the optically detected laser-induced coherent phonon oscillation of monolayers of periodic arrays of prismatic-shaped silver and gold nanoparticles, assembled by using the technique of nanosphere lithography. In this method, the same size of polystyrene sphere and the same vacuum conditions are used. Under these circumstances, the gold nanoprisms formed are found to have sharper tips than the corresponding silver nanoprisms. For both gold and silver nanoparticles, the surface plasmon absorption maximum is found to depend linearly on size. The coherent lattice oscillation periods are also found to depend linearly on size. However, although the observed dependence for the silver nanoparticle is found to follow the calculated dependence of a single particle on size (based on a one-dimensional standing wave model), the gold nanoparticle deviates from this model, and the deviation is found to increase with the size of the nanoparticles. This deviation can be explained by considering interparticle coupling. A simple interparticle lattice oscillating dipolar coupling model of the dimer is found to qualitatively account for both the sign and the size dependence of the deviation. The absence of this deviation in the silver nanoparticle arrays is blamed on the weak interparticle coupling due to their rounded tips and the possibility of oxidation of their surfaces.},
	isbn = {1520-6106},
	doi = {10.1021/jp0526647},
	url = {http://dx.doi.org/10.1021/jp0526647},
	author = {Huang, Wenyu and Qian, Wei and El-Sayed, Mostafa A}
}
@proceedings {817,
	title = {Optically detected coherent picosecond lattice oscillations in two dimensional arrays of gold nanocrystals of different sizes and shapes induced by femtosecond laser pulses},
	volume = {5927},
	year = {2005},
	pages = {592701},
	abstract = {The nanosphere lithography (NSL) technique is used to make periodic gold array of prismatic nanoparticles. We use the femtosecond time resolved double beam transient optical detection to determine the coherent lattice oscillation in gold nanoparticles. Coherent lattice oscillation is compared on gold nanoparticles of different sizes and shapes. The effect of changing shape on the oscillation period was studied. Different environmental effects on the coherent lattice oscillation are eliminated by measuring the oscillation of the prismatic shape before and after we anneal it to spherical shape of the same number of atoms. A large change in the oscillation period is observed which agrees with the calculated period using different equations for the corresponding shapes.},
	doi = {10.1117/12.620501},
	url = {http://dx.doi.org/10.1117/12.620501},
	author = {Huang, Wenyu and Qian, Wei and El-Sayed, Mostafa A}
}
@article {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 {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}
}
