New Insights of Charge Transfer at Metal/Semiconductor Interfaces for Hot-Electron Generation Studied by Surface-Enhanced Raman Spectroscopy.

Plasmonic nanostructures with hot spots are very efficient in generating energetic (hot) electrons to realize light-driven chemical reactions. This effect primarily originates from high electric fields with nonuniform distribution in the hot-spot area. However, charge-transfer (CT) at plasmonic nanostructure interfaces and its effect on hot-electron generation have not been explored in detail. Here, a series of semiconductor/metal interfaces, with continuously adjustable energy-band structures, were constructed by the assembly of Cd x Zn 1- x S supports and Au nanoparticles (NPs) interconnected with p -aminothiophenol (PATP) molecules. The plasmon-mediated oxidation of PATP embedded in Cd x Zn 1- x S/PATP/45 nm-Au NP molecular junctions was systematically investigated using gap-mode-liked surface-enhanced Raman spectroscopy (SERS). Combining in situ SERS studies with energy-level analysis, interfacial CT was found to be a primary determinant of hot-electron-induced oxygen activation on large Au NP surfaces. This study provides a new perspective on the hot-electron generation mechanism to facilitate the rational design of efficient plasmonic photocatalysts.