Tip-Enhanced Raman Imaging of Photocatalytic Processes at the Nanoscale

Over the past decade, tip-enhanced Raman spectroscopy (TERS), an emerging analytical technique that provides single-molecule sensitivity and subnanometer spatial resolution, was broadly utilized to investigate fundamental physics of plasmon-driven catalysis, as well as to examine photocatalytic properties on mono and bimetallic nanostructures. In TERS, coherent oscillations of conductive electrons, which are also known as localized surface plasmon resonances (LSPRs), are induced by light at the apex of metalized scanning probes. LSPRs (i) enhance Raman scattering from molecules located directly under the scanning probe, as well as (ii) decay producing hot carriers, highly energetic species that can catalyze a large spectrum of chemical reactions. Consequently, TERS allows for both in situ catalysis and visualization of chemical reactions in the probe-sample junction. This Perspective critically discusses mechanism of plasmon-driven catalysis and photocatalytic properties of noble metal nanomaterials. It also demonstrates the advantage of TERS in nanoscale imaging of photocatalytic reactions on bimetallic nanostructures, including gold-platinum and gold-palladium nanoplates. Finally, this Perspective provides an outlook for the future of TERS in photochemistry and material sciences.