Since to describe the dependence of the charge-transfer resonance of Raman measurements in nanosized semiconductor–molecule–metal interfaces as a function of the excitation energy with four models (Cu–ZnO–PATP–Ag, Cu–Ag–PATP–ZnO, Cu–ZnO–Ag–PATP, and Cu–Ag–ZnO–PATP assemblies) provides a powerful tool to study the chemical mechanism of surface enhanced Raman scattering (SERS), the current project measured the SERS spectra of self-assembled p-aminothiophenol (PATP) molecule junctions at 488, 514, 633, and 785 nm excitation wavelengths.
The project followed changes at the molecule junctions during the conditioning and eventually effect of charge-transfer (CT) through molecule–ZnO interfaces. The results demonstrate that the interaction between the semiconductor bands and molecular energy levels can lead to novel charge behavior. The typical ZnO-PATP interfacial electron–hole recombination causes an increase in the CT resonance enhancement of Raman scattering, which is mainly responsible for the drastic change in molecular polarizability. Researchers also proposed a complementary interpretation of the mechanism responsible for the highly variable enhancement observed in SERS. (publisher abstract modified)