Geometric\nand Electronic Structure Modulation to Optimize\nthe Charge Transfer of TiO<sub>2</sub> for Ultrasensitive and Stable\nSERS Sensing

Exploring the relationship between semiconductor structure\nand\nsurface-enhanced Raman scattering (SERS) activity was essential for\nthe development of ultrasensitive SERS substrates. Herein, we report\nan ytterbium atomic doping strategy to render TiO<sub>2</sub> (Yb-TiO<sub>2</sub>) highly SERS sensitive superior to pure TiO<sub>2</sub>,\nwith a detection limit as low as 1 × 10<sup>–9</sup> M\nfor 4-mercaptobenzoic acid. First-principles density functional theory\ncalculations reveal that ytterbium doping leads to high electrostatic\nproperties, allowing for significant charge transfer from molecules\nto semiconductors. Theoretical and experimental results indicate that\nYb-TiO<sub>2</sub> has a smaller band gap and higher density of states,\nwhich effectively enhance charge transfer between molecules and substrates,\nresulting in significant SERS activity. More importantly, Yb-TiO<sub>2</sub> was particularly stable in air and acid solution and can\nbe used for trace molecule detection in extreme environments. We demonstrate\na promising approach to construct ultrasensitive SERS by optimizing\nthe electronic structure induced by geometric structures.