Study of charge transfer effect in Surface-Enhanced Raman scattering (SERS) by using Antimony-doped tin oxide (ATO) nanoparticles as substrates with tunable optical band gaps and free charge carrier densities

Surface-enhanced Raman scattering (SERS) has been applied in many fields, but still has the limitation of widespread applications on semiconductor substrates. In this work, a series of antimony-doped tin oxide (ATO) nanoparticles (NPs) have been synthesized by a hydrothermal method and were used as SERS substrates for the first time. Interestingly, a charge transfer (CT) effect was revealed between the probing molecules of 4-mercaptobenzoic acid (4-MBA) and the substrates of ATO NPs, which accounts for the SERS enhancement and shows dependence to the Sb ions doping ratios in ATO NPs. By considering the energy level diagram of the ATO-MBA complexes and the doping theory of semiconductors, this phenomenon is believed to connect to the variance of the optical band gap energy (E-g), which is accompanied with the changes of free charge carrier densities in conduction bands (CBs) of ATO NPs due to different doping contents. The study of the E-g- or free-charge-carrier-density-dependent property of the semiconductor-based SERS provides a new point of view for the development of new semiconductor SERS substrates and also contributes to the SERS CT mechanism. (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

In this study, a series of antimony-doped tin oxide nanoparticles were synthesized and used as SERS substrates for the first time, revealing a dependence of the SERS enhancement on the doping ratios. The research indicates a connection between the enhancement effect and the variation of optical band gap energy and free charge carrier densities in conduction bands of the nanoparticles. This provides a new perspective for the development of semiconductor-based SERS substrates and contributes to the understanding of the SERS charge transfer mechanism.