Geometric and Electronic Structure Modulation to Optimize the Charge Transfer of TiO₂ for Ultrasensitive and Stable SERS Sensing

Exploring the relationship between semiconductor structure and surface-enhanced Raman scattering (SERS) activity was essential for the development of ultrasensitive SERS substrates. Herein, we report an ytterbium atomic doping strategy to render TiO₂ (Yb-TiO₂) highly SERS sensitive superior to pure TiO₂, with a detection limit as low as 1 × 10^-9 M for 4-mercaptobenzoic acid. First-principles density functional theory calculations reveal that ytterbium doping leads to high electrostatic properties, allowing for significant charge transfer from molecules to semiconductors. Theoretical and experimental results indicate that Yb-TiO₂ has a smaller band gap and higher density of states, which effectively enhance charge transfer between molecules and substrates, resulting in significant SERS activity. More importantly, Yb-TiO₂ was particularly stable in air and acid solution and can be used for trace molecule detection in extreme environments. We demonstrate a promising approach to construct ultrasensitive SERS by optimizing the electronic structure induced by geometric structures.