Observation of Enhanced Raman Scattering for Molecules Adsorbed on TiO2 Nanoparticles: Charge-Transfer Contribution

Surface-enhanced Raman scattering from molecules adsorbed on TiO2 nanoparticles has been observed. This is attributed to the dominant contribution of the TiO2-to-molecule charge-transfer mechanism. The charge-transfer process is largely dependent on the intrinsic nature of the adsorbed molecules and the surface properties of the semiconductor. Both the stronger electron attracting ability of groups para- to the mercapto group bonded with TiO2 surface and the plentiful surface states of TiO2 nanoparticles are favorable to TiO2-to-molecule charge-transfer and SERS for molecules adsorbed on TiO2.