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Full-Text Articles in Nanoscience and Nanotechnology

Gold Nanoparticles Propulsion From Surface Fueled By Absorption Of Femtosecond Laser Pulse At Their Surface Plasmon Resonance, Wenyu Huang, Wei Qian, Mostafa A. El-Sayed Jan 2006

Gold Nanoparticles Propulsion From Surface Fueled By Absorption Of Femtosecond Laser Pulse At Their Surface Plasmon Resonance, Wenyu Huang, Wei Qian, Mostafa A. El-Sayed

Wenyu Huang

Femtosecond laser irradiation of assembled nanoprisms on a quartz substrate at their strong absorbing surface plasmon resonance frequency causes their propulsion from the substrate. SEM and AFM show that the particles fly while keeping their prismatic shape, but they decrease in size by an amount that can be calculated assuming atomic sublimation. Several mechanisms are mentioned, but the sublimation mechanism, which rapidly builds up pressure under the particle and propels it away from substrate, is discussed in detail. From the kinetic energy given to the flying nanoparticle, an initial velocity of ∼160 m/s (∼360 miles/h) is calculated. The dependence of …


Photothermal Reshaping Of Prismatic Au Nanoparticles In Periodic Monolayer Arrays By Femtosecond Laser Pulses, Wenyu Huang, Wei Qian, Mostafa A. El-Sayed Jan 2005

Photothermal Reshaping Of Prismatic Au Nanoparticles In Periodic Monolayer Arrays By Femtosecond Laser Pulses, Wenyu Huang, Wei Qian, Mostafa A. El-Sayed

Wenyu Huang

Prismatic goldnanoparticles 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 …


The Optically Detected Coherent Lattice Oscillations In Silver And Gold Monolayer Periodic Nanoprism Arrays:  The Effect Of Interparticle Coupling, Wenyu Huang, Wei Qian, Mostafa A. El-Sayed Jan 2005

The Optically Detected Coherent Lattice Oscillations In Silver And Gold Monolayer Periodic Nanoprism Arrays:  The Effect Of Interparticle Coupling, Wenyu Huang, Wei Qian, Mostafa A. El-Sayed

Wenyu Huang

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 …


Coherent Vibrational Oscillation In Gold Prismatic Monolayer Periodic Nanoparticle Arrays, Wenyu Huang, Wei Qian, Mostafa A. El-Sayed Jan 2004

Coherent Vibrational Oscillation In Gold Prismatic Monolayer Periodic Nanoparticle Arrays, Wenyu Huang, Wei Qian, Mostafa A. El-Sayed

Wenyu Huang

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 …