This talk describes two recent projects where we have used a combination of experiments and theory to study the excited state dynamics of gold nanoparticles and semiconductor nanocrystals on time scales from 100 fs to many ns.  In both cases the initial electronic excitation undergoes dephasing and relaxation, exciting phonons in the nanoparticles, and then evolving to heat in the surrounding solvent.  Connections with photocatalysis will be discussed.In a project that was done with Emily Weiss, we considered the influence of ligands on the time-resolved absorption spectrum of gold nanoparticles.  Here we used electronic structure calculations to show that the ligands contribute significantly to the plasmonic density of states, and also influence the electron-phonon coupling strength.  As a result as a result, the ligands play a crucial role in the rate of energy flow between electrons and phonons, and also the flow of energy to the surrounding solvent.A project with Richard Schaller concerns CdSe and other nanocrystals, where we have modeling time-resolved photoluminescence and FSRS experiments.  Here the initially excited states relax to the band gap, leading to phonon excitation which vibronically assists emission from the band-gap state.  Subsequently the phonon energy flows to the solvent with a rate that is determined by solvent thermal diffusion.

Modeling excited state dynamics in nanoparticles and nanocrystals

246th National Meeting (2013)

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