A dual strategy integrating “geometric design” and “defect engineering” for tuning SERS performance on non-noble metal substrates

Research on surface-enhanced Raman scattering (SERS) substrates free of noble metals continues to encounter considerable challenges. In this work, a dual-strategy integrating “geometric design” and “defect engineering” is employed to substantially enhance SERS performance. Initially, a pristine-C@TiO 2 @W 18 O 49 composite structure was precisely fabricated via a hydrothermal route. By utilizing the Mie resonance effect generated by the submicron structure of C@TiO 2 , stable electromagnetic hotspots are produced in the near-field region. Subsequently, photoreduction generates abundant oxygen vacancies (OVs) in WO 3 , thereby introducing defect energy levels (Vo) into its band structure and enhancing the charge transfer (CT) efficiency. Through synergistic Mie resonance effects and CT enhancement, this material exhibits remarkable SERS performance toward Rhodamine 6G (R6G), with a detection limit (LOD) of 7.12 × 10 −7 mol/L and an enhancement factor (EF) as high as 1.16 × 10 7 . Moreover, composite material exhibits excellent specific detection for a series of dye molecules (MB, CV, and RhB). This study proposes a novel approach for developing low-cost, high-performance SERS substrates through the coupled effects of electromagnetic enhancement and tunable oxygen vacancy energy levels.