Surface-Enhanced Raman Scattering from Synergistic Contribution of Metal and Semiconductor in TiO₂/MBA/Ag(Au) and Ag(Au)/MBA/TiO₂ Assemblies

Abstract

Traditional metal SERS-active substrate (Ag or Au) and novel semiconductor SERS-active substrate (TiO2) are combined into the composite system for their synergetic contribution to SERS. A series of assemblies with 4-mercaptobenzoic acid (4-MBA) molecule, TiO2, and/or Ag (Au) nanoparticles (NPs) have been fabricated by a self-assembly method. In the sandwich-structure assemblies (TiO2/MBA/Ag(Au) and Ag(Au)/MBA/TiO2), the SERS signals of 4-MBA molecule exhibit obvious difference in not only the intensity but also Raman frequency as compared with that SERS enhancement in the TiO2/MBA, which is attributed to the introduce of metals and its interaction/synergistic action with TiO2 NPs. SERS enhancement behaviors of 4-MBA in the sandwich-structure assemblies strongly depend on the natures of metals and 4-MBA molecule, which can result in a influence on the TiO2-to-molecule charge transfer and consequent additional EM field effect. This work would like to be interesting and of considerable value for both theory development and practice application of SERS technology.