Charge transfer enhancement in the surface-enhanced Raman scattering of Ta2O5 superstructures

Semiconductor nanomaterials with the surface-enhanced Raman scattering (SERS) sensitivity are gradually attracting more and more attention due to their particular advantages. However, the wider applications of semiconductor SERS-active substrates still require considerable effort to improve their SERS sensitivity. An excellent enhancement of Raman scattering is achieved by Ta2O5 superstructures with a mean diameter of 29 nm. The Ta2O5 superstructure is constructed by crystallized Ta2O5 quantum dots with an average diameter of 2.39 nm and exhibits a very low detection limit of 10−7 M for both methyl violet and methylene blue molecules under the irradiation of 532 nm laser. The chemical enhancement, originating from the precise matching of energy levels and the facile charge transfer between Ta2O5 superstructures and dye molecules, predominantly contributes to the Raman enhancement. The detailed band structure analysis in this work does a good demonstration for achieving the energy level matching and charge transfer enhancement in semiconductor SERS-active substrates with the probed molecules.