Using a model metal–semiconductor–molecule–metal assembly designed for probing the charge-transfer (CT) mechanism of surface-enhanced Raman scattering (SERS), the current project measured the SERS of ZnO–PATP–Ag, Au–ZnO–PATP–Ag, and Cu–ZnO–PATP–Ag assemblies at excitation wavelengths of 514.5, 785, and 1064 nm.
The results demonstrate that the metal–semiconductor contact can alter the charge distribution through p-aminothiophenol (PATP) molecules. This is attributed to the chemical SERS enhancement mechanism with additional electrical transport properties within these assemblies. These inhibit the CT from the metal to the molecule, resulting in the different degrees to which CT contributes to the overall SERS enhancement of PATP. (publisher abstract modified)