New Insights of Charge Transfer at Metal/Semiconductor Interfacesfor Hot-Electron Generation Studied by Surface-Enhanced RamanSpectroscopy

Plasmonic nanostructures with hot spots are very efficient in generatingenergetic (hot) electrons to realize light-driven chemical reactions. This effect primarilyoriginates from high electricfields with nonuniform distribution in the hot-spot area. However,charge-transfer (CT) at plasmonic nanostructure interfaces and its effect on hot-electrongeneration have not been explored in detail. Here, a series of semiconductor/metal interfaces,with continuously adjustable energy-band structures, were constructed by the assembly ofCdxZn1-xS supports and Au nanoparticles (NPs) interconnected withp-aminothiophenol(PATP) molecules. The plasmon-mediated oxidation of PATP embedded in CdxZn1-xS/PATP/45 nm-Au NP molecular junctions was systematically investigated using gap-mode-liked surface-enhanced Raman spectroscopy (SERS). Combining in situ SERS studies withenergy-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 onthe hot-electron generation mechanism to facilitate the rational design of efficient plasmonicphotocatalysts.