High performance and recyclable Au-Ag/TiO2/PS substrate for the detection of organic pollutants

A highly sensitive and recyclable surface-enhanced Raman scattering (SERS) substrate was successfully fabricated through in situ reduction of bimetallic gold-silver nanoparticles (Au-Ag NPs) on vertically aligned titanium dioxide nanorods (TiO ₂ NRs) grown on porous silicon (PS). The as-prepared Au-Ag/TiO ₂ /PS substrate demonstrated exceptional SERS performance for the detection of crystal violet (CV), reaching a low detection limit (LOD) of 10 ^− 11 M and a high enhancement factor (EF) of 1.74×10 ⁷ . This superior performance can be attributed to the synergistic effect of the appropriately sized Au-Ag NPs with nanoscale interparticle gaps that generate intense localized surface plasmon resonance (LSPR), as well as the large surface area of PS, which facilitates analyte enrichment. Moreover, the substrate exhibited excellent photocatalytic self-cleaning capability under UV irradiation. The rapid generation of non-equilibrium carriers within the TiO ₂ NRs, the directional transfer and efficient charge separation at the Au-Ag/TiO ₂ Schottky junction, together with the abundant active sites on PS, collectively contribute to the effective degradation of adsorbed CV molecules. Notably, the substrate maintains excellent recyclability and stability even after five consecutive cycles. These findings offer valuable insights for the design of multifunctional SERS platforms for the detection and degradation of organic pollutants.