Local photochemical nanoscopy of hot-carrier-driven catalytic reactions using plasmonic nanosystems

Nanoscale investigation of the reactivity of photocatalyticsystemsis crucial for their fundamental understanding and improving theirdesign and applicability. Here, we present a photochemical nanoscopytechnique that unlocks the local spatial detection of molecular productsduring plasmonic hot-carrier-driven photocatalytic reactions withnanometric precision. By applying the methodology to Au/TiO2 plasmonic photocatalysts, we experimentally and theoretically determinedthat smaller and denser Au nanoparticle arrays present lower opticalcontribution with quantum efficiency in hot-hole-driven photocatalysisclosely related to the population heterogeneity. As expected, thehighest quantum yield from a redox probe oxidation is achieved atthe plasmon peak. Investigating a single plasmonic nanodiode, we unravelthe areas where oxidation and reduction products are evolved withsubwavelength resolution (similar to 200 nm), illustrating the bipolarbehavior of such nanosystems. These results open the way to quantitativeinvestigations at the nanoscale to evaluate the photocatalytic reactivityof low-dimensional materials in a variety of chemical reactions.