Ag₂O-decorated TiO₂ for ultrasensitive SERS detection of crystal violet

Surface-enhanced Raman scattering (SERS) technology has emerged as a powerful analytical tool for trace-level environmental pollutant detection, with its performance critically dependent on the physicochemical properties of substrate materials. While noble metal substrates (e.g., Au/Ag) demonstrate superior SERS enhancement through surface plasmon resonance (SPR), their practical deployment is hampered by inherent limitations including high material costs and susceptibility to oxidation-induced degradation. Herein, we report the rational design of Ag₂O/TiO₂ composite substrates via a facile wet-chemical precipitation method, wherein Ag₂O nanoparticles are uniformly decorated onto pre-synthesized TiO₂ nanospheres. Upon application in crystal violet (CV) detection, the optimized Ag₂O/TiO₂ composite substrate exhibits remarkable SERS performance with an enhancement factor (EF) of 6.7 × 10⁶ and an ultra-low detection limit (LOD) of 1.0 nM (1.0 × 10⁻⁹ M). Systematic investigations reveal that the Ag₂O modification induces photogenerated electron accumulation on the TiO₂ surface, promoting photoinduced charge transfer (PICT) between the substrate and adsorbed CV molecules. This work not only presents a cost-effective and stable SERS platform for environmental contaminant monitoring but also provides mechanistic insights into the rational engineering of semiconductor-based SERS substrates with enhanced sensitivity and durability.