Charge Transfer in 4-Mercaptobenzoic Acid-Stabilized Au Nanorod@Cu₂O Nanostructures: Implications for Photocatalysis and Photoelectric Devices

Nanoscale materials have an irreplaceable advantage in solar energy utilization because of their perfect match with visible light wavelength on the length scale. Charge transfer (CT) between a metal nanoparticle and contacted nanoscale semiconductor plays a significant role in photoinduced energy transfer. Here, we fabricated a new complex, a gold nanorod-4-mercaptobenzoic acid@Cu2O (Au NR-MBA@Cu2O) core–shell nanostructure, and used surface-enhanced Raman scattering (SERS) spectroscopy of the interlayer MBA molecules to investigate the CT process occurring between the Au NRs and Cu2O. In our system, different surface plasmon absorption bands were adjusted by tuning the thicknesses of the Cu2O shells on the Au NR core to explore the influence of plasmon absorption at different incident Raman laser lines. By analyzing the SERS spectra, the degree of CT was calculated, and the consequences can be fully explained by photoexcitation across interface electron transfer and plasmon-induced interfacial charge transfer transition at laser excitation wavelengths of 633 and 785 nm. This experiment introduced a simple, effective, and intuitive approach to observe the CT process in metal semiconductors by SERS. The results of our study will improve in photocatalytic efficiency and photoelectric devices.