SERS as a probe for the charge-transfer process in a coupled semiconductor nanoparticle system TiO2/MBA/PbS

Abstract

A coupled semiconductor nanoparticle system composed of TiO₂ NPs, 4-mercaptobenzoic acid (4-MBA) molecules and PbS NPs has been fabricated as a model to study the involved charge transfer (CT) effect using a Surface-Enhanced Raman Scattering (SERS) technique. In this TiO₂/MBA/PbS system, the MBA molecules function as both a linker between TiO₂ and PbS NPs and a SERS probe to reveal the CT process. For the SERS enhancement behaviors of the CT-sensitive vibrational mode in 4-MBA and the Raman spectra of the phonon vibrational mode in TiO₂ NPs, there are some evident changes after adding PbS to the TiO₂/MBA system. These changes are due to the interaction between TiO₂ NPs and PbS NPs. We found that these differences, closely related to the natures of TiO₂ and PbS NPs, are a reflection of the enhanced TiO₂-to-molecule CT process in SERS. The SERS spectra of the TiO₂/MBA/CdS system were also investigated and the result is in good accordance with our theory. This work will not only help in constructing nanoscale models to study interfacial CT processes but also be of considerable value for practical application of SERS technology.