Plasmonic materials offer a promising approach for developing new light harvesting devices and for directing the outcome of chemical reactions. Their ability to concentrate light to nanometer<sup>3</sup> volumes leads to the formation of hot spots and hot electron generation, which can modify potential energy surfaces, direct energy flow, and enable new photochemical and photophysical processes.  Currently, a fundamental mechanistic understanding of how photoreactions occur at plasmonic surfaces is lacking. We utilize ultrafast Raman techniques to follow structural dynamics in molecules adsorbed to or proximal to plasmonic materials, providing picosecond and femtosecond scale information on bond-making and bond-breaking processes.<br/><br/>This talk will focus on the use of various time-resolved surface-enhanced Raman spectroscopies to follow chemical reaction dynamics of molecular plasmonic systems. Both femtosecond and picosecond Raman spectroscopies, coupled with a femtosecond plasmon excitation pulse, will be discussed. Two systems of interest will be examined: the plasmonically-enhanced breakdown of an organic pollutant, and a plasmonically-enhanced electron transfer process. In both systems, we consider the roles of hot spot formation and hot electron generation in driving the relevant photochemistry.  By obtaining time-resolved structural snapshots of molecules reacting on the ultrafast timescale of nuclear motion, we are able to determine the impact of the plasmon on the reaction mechanism and rate.  Efforts to determine plasmon shape effects on reaction dynamics at the single particle level will also be discussed.  We anticipate that our fundamental research will lead to exciting developments in the use of plasmonic systems to drive photochemical and photophysical processes.

Following plasmonically-enhanced chemical reactions with ultrafast Raman spectroscopies

249th National Meeting (2015)

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