@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 {1129,
	title = {Photothermally excited coherent lattice phonon oscillations in plasmonic nanoparticles},
	journal = {European Physical Journal-Special Topics},
	volume = {153},
	year = {2008},
	note = {Huang, W. El-Sayed, M. A.14th International Conference on Photoacoustic and Photothermal Phenomena/1st US-Egypt Workshop on Photoacoustic and Photothermal PhenomenaJan 07-11, 2007Cairo, EGYPT},
	month = {Jan},
	pages = {325-333},
	abstract = {The photothermal property of (Ag and Au) plasmonic nanoparticles has brought about many important discoveries and applications in nanoscience and nanotechnology. In this review, we briefly summarize a photothermal effect, the coherent phonon oscillation, of plasmonic nanoparticles irradiated with ultrafast laser pulses of low power density. The coherent phonon oscillation is created in the nanoparticle by the ultrafast impulsive photothermal heating. The effects of size, shape, thickness, and interparticle interaction on the period of coherent phonon oscillations are discussed. The detection of the coherent lattice oscillation of metallic nanoparticles provides a powerful tool to characterize the mechanical and structural properties of nanostructures.},
	isbn = {1951-6355},
	doi = {10.1140/epjst/e2008-00456-x},
	author = {Huang, Wenyu and El-Sayed, Mostafa A}
}
@article {1130,
	title = {Pulsed laser photothermal annealing and ablation of plasmonic nanoparticles},
	journal = {European Physical Journal-Special Topics},
	volume = {153},
	year = {2008},
	note = {Huang, W. El-Sayed, M. A.14th International Conference on Photoacoustic and Photothermal Phenomena/1st US-Egypt Workshop on Photoacoustic and Photothermal PhenomenaJan 07-11, 2007Cairo, EGYPT},
	month = {Jan},
	pages = {223-230},
	abstract = {In this review, we briefly summarize the photothermal properties of plasmonic nanoparticles. Several photothermal effects of plasmonic nanoparticles irradiated with ultrafast laser pulses of various powers are introduced. Plasmonic nanoparticles have been synthesized by pulsed laser ablation of bulk materials. Melting and ablation of nanoparticles have also been used to modify the shape and the size distribution of plasmonic nanoparticle samples. Under certain circumstances, another interesting observation using high power femtosecond laser irradiation of plasmonic nanoparticles is also included in this review, namely the flying, by propulsion of the plasmonic nanoparticles.},
	isbn = {1951-6355},
	doi = {10.1140/epjst/e2008-00432-6},
	author = {Huang, Wenyu and El-Sayed, Mostafa A}
}
@article {1132,
	title = {Time-resolved investigation of the acoustic vibration of a single gold nanoprism pair},
	journal = {Journal of Physical Chemistry C},
	volume = {112},
	number = {30},
	year = {2008},
	note = {Burgin, J. Langot, P. Del Fatti, N. Vallee, F. Huang, W. El-Sayed, M. A.},
	month = {Jul},
	pages = {11231-11235},
	abstract = {The acoustic vibration of single gold nanoprism pairs on a glass substrate has been investigated in the time-domain combining a spatial modulation spectroscopy microscope with a high-sensitivity femtosecond pump-probe setup. Three modes were observed and ascribed to two in-plane and one out-of-plane vibration of the nanoprisms forming the pair, in agreement with a theoretical analysis. The periods of the two former modes with similar nature show weak (about 10\%) and well correlated pair to pair fluctuations that can be unambiguously ascribed to variation of the prism geometry. In contrast, strong fluctuations, by almost a factor of 6, of the mode damping are evidenced with no correlation with their period. This indicates large variations of the prism-substrate coupling, providing a unique way for its local investigation.},
	isbn = {1932-7447},
	doi = {10.1021/jp802365s},
	author = {Burgin, J. and Langot, P. and Del Fatti, N. and Vallee, F. and Huang, Wenyu 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 {1137,
	title = {On the universal scaling behavior of the distance decay of plasmon coupling in metal nanoparticle pairs: A plasmon ruler equation},
	journal = {Nano Letters},
	volume = {7},
	number = {7},
	year = {2007},
	note = {Jain, Prashant K. Huang, Wenyu El-Sayed, Mostafa A.},
	month = {Jul},
	pages = {2080-2088},
	abstract = {Localized surface plasmon resonances (LSPR) in lithographically fabricated gold (Au) nanodisc pairs are investigated using microabsorption spectroscopy and electrodynamic simulations. In agreement with previous work, we find that the fractional plasmon wavelength shift for polarization along the interparticle axis decays nearly exponentially with the interparticle gap. In addition, we find that the decay length is roughly about 0.2 in units of the particle size for different nanoparticle size, shape, metal type, or medium dielectric constant. The near-exponential distance decay and the interesting "universal" scaling behavior of interparticle plasmon coupling can be qualitatively explained on the basis of a dipolar-coupling model as being due to the interplay of two factors: the direct dependence of the single-particle polarizability on the cubic power of the particle dimension and the decay of the plasmonic near-field as the cubic power of the inverse distance. Using this universal scaling behavior, we are able to derive a "plasmon ruler equation" that estimates the interparticle separation between Au nanospheres in a biological system from the observed fractional shift of the plasmon band. We find good agreement of the interparticle separations estimated using this equation with the experimental observations of Reinhard et al.},
	isbn = {1530-6984},
	doi = {10.1021/nl071008a},
	author = {Jain, Prashant K and Huang, Wenyu 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 {1155,
	title = {Using silica films and powders modified with benzophenone to photoreduce silver nanoparticles},
	journal = {Journal of Photochemistry and Photobiology a-Chemistry},
	volume = {181},
	number = {2-3},
	year = {2006},
	note = {Eustis, Susie Krylova, Galina Smirnova, Natalie Eremenko, Anna Tabor, Christopher Huang, Wenyu El-Sayed, Mostafa A.},
	month = {Jul},
	pages = {385-393},
	abstract = {Porous silica (SiO2 films and powders), modified with benzophenone (BP), facilitates the formation of stable sliver nanoparticles by taking advantage of the solid supported photosensitizer. The silica serves as a carrier for the BP into an aqueous solution and its subsequent removal. Benzophenone, bound to a silica film, was able to reduce silver ions to generate nanoparticles in solution, while silica powder with bound BP generates silver nanoparticles that are attracted to the silica. Silver nanoparticles are also fabricated in porous silica films by incorporating silver ions into the films before casting and then irradiating the film in a solution containing BP. From pH studies, it is concluded that the ketyl-radicals and anion-radicals of BP and IPA both take part in the reduction of silver ions. These synthetic studies provide a new photochemical reduction method by immobilizing the reactant on a silica surface allowing generation of silver nanoparticles in solution attached to powders or inside a film for catalytic applications or increased conductivity of silica films. (c) 2006 Elsevier B.V. All rights reserved.},
	isbn = {1010-6030},
	doi = {10.1016/j.jphotochem.2005.12.024},
	author = {Eustis, Susie and Krylova, G. and Smirnova, N. and Eremenko, A. and Tabor, C. E. and Huang, Wenyu and El-Sayed, Mostafa A}
}
@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}
}
