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

## TL;DR

A new Raman spectroscopy method using silver-dotted titanium dioxide nanocomposites improves detection of hard-to-measure molecules for applications like environmental monitoring and diagnostics.

## Contribution

A novel PIERS platform using Ag-dot TiO2 nanocomposites significantly enhances Raman signals for weak-Raman-response molecules.

## Key findings

- PIERS achieved an 8.9-fold Raman signal enhancement over standard SERS for Congo red.
- The PIERS platform reliably detected trace levels of thiram and urea.
- Signal enhancement depends on pre-irradiation duration and recovery time of the substrates.

## 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.

In this work, a photo-induced enhanced Raman spectroscopy (PIERS) platform based on Ag-dotted TiO2 nanocomposites was developed to overcome the limitations of conventional SERS in detecting weak-Raman-response molecules.