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dc.contributor.advisor Halas, Naomi J.
dc.creatorWestcott, Sarah Linda
dc.date.accessioned 2009-06-04T07:58:02Z
dc.date.available 2009-06-04T07:58:02Z
dc.date.issued 2001
dc.identifier.urihttp://hdl.handle.net/1911/18049
dc.description.abstract In metallic nanostructures, the interaction of excited electrons with the nanostructure surface may result in electron relaxation dynamics that are significantly different than those predicted by electron-lattice coupling. These ultrafast electron dynamics were monitored by pump-probe measurements of the time-resolved change in transmission. Using femtosecond pulses from a cavity-dumped titanium-doped sapphire laser, two types of nanoparticles with a core-shell geometry were studied. Nanoshells are nanoparticles with a dielectric core surrounded by a continuous thin metal shell. For nanoshells, the plasmon resonance wavelength is tunable by changing the core and shell dimensions. For nanoshells with a gold sulfide core and a gold shell, two conditions were observed under which electron relaxation was different than predicted by electron-phonon coupling. First, electron relaxation occurred more rapidly for gold-gold sulfide nanoshells embedded in polymer films than for nanoshells dispersed in water, with lifetimes of 1.6 ps and 3 to 5 ps, respectively. Second, for nanoshells dispersed in water, the electron relaxation lifetime decreased with adsorption of p-aminobenzoic acid (to 1.7 ps) or aniline (to 1.9 ps) on the nanoshells. With adsorbed n-propylamine or p-mercaptobenzoic acid, electron relaxation transpired in 2.8 ps or 2.4 ps, respectively. Density functional theory calculations indicated that the molecules leading to the fastest electron relaxation possessed the largest induced dipole moments near a metal surface. Semicontinuous gold films grown around a silica nanoparticle core exhibited spectral and dynamical optical signatures of the percolation threshold. Compared to continuous shells, the electron dynamics in the semicontinuous shell layer were dramatically different as additional induced bleaching was observed in the first 500 fs. The observed dynamics are consistent with a rate equation model in which the electrons are initially excited in localized surface plasmons or "hot spots" and subsequently achieve an equilibrium with electrons throughout the film on a timescale faster than electron-phonon thermalization.
dc.format.extent 112 p.
dc.format.mimetype application/pdf
dc.language.iso eng
dc.subjectElectronics
Electrical engineering
Optics
dc.title Ultrafast electron dynamics in gold nanoshells
dc.type.genre Thesis
dc.type.material Text
thesis.degree.department Physics
thesis.degree.discipline Natural Sciences
thesis.degree.grantor Rice University
thesis.degree.level Doctoral
thesis.degree.name Doctor of Philosophy
dc.identifier.citation Westcott, Sarah Linda. "Ultrafast electron dynamics in gold nanoshells." (2001) PhD diss., Rice University. http://hdl.handle.net/1911/18049.


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