Silver-dotted titanium dioxide nanocomposites for highly efficient photo-induced enhanced Raman spectroscopy in trace detection of weak-Raman-response molecules

Abstract

Surface-enhanced Raman spectroscopy (SERS) enables highly sensitive molecular detection, including single-molecule analysis, for species with strong Raman scattering. However, conventional SERS platforms often fail to detect analytes with inherently weak Raman responses, limiting their applicability in trace sensing of these molecules. Here, we present photo-induced enhanced Raman spectroscopy (PIERS) as an advanced SERS technique based on silver-dotted titanium dioxide (Ag-dot TiO₂) nanocomposite (NC) substrates, which synergistically integrate plasmonic Ag nanoparticles with photo-activated TiO₂ to significantly amplify Raman signals beyond the capability of conventional SERS. Congo red (CR), a bulky dye molecule with low Raman activity, was selected as the model analyte. The PIERS signal exhibited an 8.9-fold enhancement over standard SERS with high reliability. The enhancement was strongly dependent on both the pre-irradiation duration and recovery time of the Ag-dot TiO₂ substrates, highlighting the tunable nature of the PIERS effect. To further assess its versatility, the PIERS platform was tested on thiram (a pesticide) and urea (a small biomolecule) and demonstrated reliable trace-level detection in both cases. These obtained results establish Ag-dot TiO₂-based PIERS platform as a promising approach for ultrasensitive detection of weak-Raman-response molecules, with broad implications for environmental monitoring, food safety, and biomedical diagnostics.