Semiconducting SnO₂ nanoparticles for surface-enhanced Raman scattering applications

This study reports the synthesis of phase-pure SnO₂ nanoparticles using a sol-gel-assisted method and thermal annealing at 800 and 900 °C to optimize their structural and surface properties for non-plasmonic semiconductor-based surface-enhanced Raman scattering (SERS) applications. Comprehensive characterization using X-ray diffraction with Rietveld refinement, high-resolution electron microscopy, and X-ray photo electron spectroscopy confirmed the enhanced crystallinity, spherical morphology, and controlled generation of oxygen vacancies, particularly when annealed at 800 °C. These vacancies were found to play a critical role in facilitating charge transfer, which is the dominant enhancement mechanism in semiconductor-based SERS. Raman spectroscopy verified phonon activation and lattice coherence in post-annealed SnO₂ nanoparticles, while SERS using Nile blue as the analyte demonstrated strong signal enhancement with an estimated enhancement factor of 3.95 × 10³ and a detection limit down to 10^-6 mol L^-1. The substrate exhibited high spectral reproducibility and minimal fluorescence interference, even at low analyte concentrations. Notably, this performance was achieved without the use of noble metals or dopants, highlighting the effectiveness of defect engineering via thermal treatment. These findings establish thermally optimized SnO₂ as a robust, scalable, and cost-effective SERS platform, offering promising potential for chemical and biosensing applications.