Gold-Decorated Oxidized Porous Silicon Nanoscaffolds as SERS Platform for Plasmonic Pesticide Sensing

The exploration of innovative materials for the chemical detection of organic contaminants remains an ongoing endeavor. Pesticides are a threat to human health because they are present in water bodies, crops, and processed foods. Oxidized porous silicon (OPSi) materials offer a versatile platform for plasmonic architectures by integrating a high surface area with adjustable optical properties. In this study, a Surface-Enhanced Raman Spectroscopy (SERS) substrate was developed by decorating OPSi layers with gold nanoislands through a controlled sputter deposition process. By systematically varying the gold deposition time, we identified clear correlations between the morphology of the nanoislands, localized surface plasmon resonance characteristics, and SERS improvement of the Raman signals. Scanning electron microscopy and UV-visible reflectance spectroscopy revealed a tunable plasmonic response, optimal at a 5 s deposition, where isolated islands maximize the electromagnetic hot-spot density without percolation. The optimized architecture facilitated sensitive, label-free detection of acetamiprid as a model pesticide analyte, achieving a detection limit of less than 0.2 μg/mL (8.9 8 × 10^-7 mol/L) with a linear response from 0.2 to 15 μg/mL (8.98 × 10^-7 to 6.37 × 10^-5 mol/L). The substrate maintained spectral specificity in complex chemical environments, demonstrating that controlled gold deposition on OPSi layers produces a robust and reproducible SERS platform.