Charge-Transfer-Induced Surface-Enhanced Raman Scattering on Ag−TiO2 Nanocomposites

Abstract

In this paper, a series of silver-deposited TiO 2 (Ag−TiO 2 ) nanoparticles (NPs) with a varying content of Ag were prepared by a photoreduction method and were attempted to serve as SERS-active substrates for the first time. SERS signals of 4-MBA molecules adsorbed on Ag−TiO 2 NPs were further enhanced considerably relative to those enhancements on pure TiO 2 NPs. The surface-deposited Ag on TiO 2 can inject additional electrons into molecules adsorbed on the TiO 2 surface through the conduction band of TiO 2 NPs because of plasmon resonance absorption of Ag under incident visible laser, besides the intrinsic TiO 2 -to-molecule charge-transfer (CT) contribution. The two contributions mentioned are responsible for the whole SERS intensity of the molecules adsorbed on Ag−TiO 2 NPs. This work is valuable in developing nanosized TiO 2 used as a promising, nontoxic and biologically compatible SERS-active substrate as well as in studying the CT mechanism between Ag and TiO 2 for potential photoelectrochemical applications.