The timescale of nuclear motion associated with bond-making and -breaking processes is the femtosecond and picosecond timescale of molecular vibrations. Our lab uses ultrafast Raman spectroscopy to probe structural dynamics in complex and highly reactive systems, with approaches ranging from ultrafast surface-enhanced Raman spectroscopy to femtosecond stimulated Raman spectroscopy. In this talk, I’ll first discuss how ultrafast surface-enhanced Raman spectroscopy can inform upon the mechanisms involved in plasmonic photocatalysis, an exciting field which capitalizes on the tunable nanostructures and strong optical cross sections of plasmonic materials in order to drive photoinduced chemical reactions. Ultrafast SERS is uniquely well-suited to examining contributions from hot carriers and heating on the ultrafast timescale, and we have quantitated energy transfer from photoexcited plasmons to proximal adsorbates. We find that contributions of heating to catalysis are generally insignificant, but can play a role when surrounding oxide materials inhibit energy flow. Secondly, I’ll discuss how our use of femtosecond stimulated Raman spectroscopy can inform on the nuclear dynamics associated with charge transfer and transport in organic photovoltaic systems. By probing structural degree of freedom on the ultrafast timescale, we have shown that different functional groups play a crucial role in facilitating charge transfer. Overall, these two approaches to examining reactive chemical systems through ultrafast Raman probing highlight the importance of structurally sensitive measurements in understanding mechanisms.<br/>

Ultrafast and nanoscale Raman probes of plasmonic photocatalysis and organic photovoltaics

2019 Fall National Meeting

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