Plasmonic nanomaterials show great promise as highly selective photocatalysts, however their utility is currently limited by a lack of understanding of the ultrafast mechanisms relevant in the conversion of light to chemical energy. We have developed ultrafast surface-enhanced Raman spectroscopic (SERS) techniques to probe the dynamics in coupled plasmonic nanomaterial-molecular systems. This talk will discuss our use of ultrafast SERS to probe the contributions of plasmon-generated hot electron transfer, heating, and vibrational energy transfer on timescales relevant to photocatalysis. Specifically, we probe plasmon to molecular carrier transfer on the picosecond timescale by quantitating the growth of radical molecular species. We probe the effects of temperature on chemical reactivity by monitoring transient Stokes and anti-Stokes Raman intensities to quantify vibrational kinetic energy in adsorbates, finding that heating is not a major contributor to plasmonic photocatalysis. Finally, I’ll discuss our discovery of a highly selective plasmon-driven methyl migration reaction in which the plasmonic substrate can provide nanoscale spatial control of reactivity. These efforts in developing a fundamental understanding of plasmon-mediated processes in molecules will ultimately aid in the rational design of cost-effective plasmonic materials capable of driving chemistry using solar radiation.

Ultrafast surface enhanced Raman spectroscopic probes of plasmon-molecule dynamics

ACS Fall 2021

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