Plasmon-driven oxidation of ferrocyanide ions inside surface-enhanced Raman spectroscopy (SERS) active hot spots is studied with continuous wave (CW) pump-probe SERS. By comparing with corresponding electrochemical (EC)-SERS measurements, the characteristic SER spectral variances observed upon 532 nm optical pumping can be unambiguously identified as the oxidation process occurs to the surface species. We propose that under 532 nm optical pumping, hot-holes generated during plasmon decay are transferred to adsorbed ferrocyanide ions while hot-electrons generated at the same time are being transferred to adjacent gold nanospheres, which play the role of electron scavengers. Our observation complements previous literature that demonstrated the possibility of hot-electron transfer in the same system in the presence of hole scavengers. These findings undoubtedly shed light onto the possibility of controlling the plasmon-driven charge transfer processes by tuning the local environment and counter species. Moreover, together with the rapid progression of this reaction at relatively low laser powers and the ease to identify both the reactant and the product species with lack of undesirable byproducts, this is an ideal model system for future fundamental studies on plasmon-driven charge transfer.

Directly observing plasmon-driven oxidation of ferrocyanide using SERS: Towards a model system for plasmonic reactions

2019 Fall National Meeting

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