Tunable High-Density nanogaps in compact Ag nanowires for Surface-Enhanced Raman scattering detection of pesticide residues

Surface-enhanced Raman scattering (SERS) has become a highly effective method for detecting residues, characterized by its exceptional sensitivity, rapid detection capabilities, and minimal sample consumption. The utilization of metal nanogaps in SERS is particularly appealing due to their pronounced surface plasmon effects. Nonetheless, the challenge remains in fabricating nanoscale, high-density, tunable nanogaps, which hinders their broader practical applications. In this study, we introduce an innovative and cost-effective methodology combining atomic layer deposition (ALD) with mechanical rolling to produce compact silver nanowires (Ag NWs) featuring tunable and densely packed nanogaps. The synthesized Ag NWs exhibit remarkable SERS sensitivity, achieving a detection limit (LOD) of 10-11 M for Rhodamine 6G (R6G), alongside excellent signal stability and reproducibility. Additionally, these high-density nanogap Ag NWs demonstrate efficacy in detecting the pesticide thiram in alcohol, with a LOD reaching 0.02 ppm. Moreover, they are capable of identifying thiram residues on apple peels, with a detection limit of 2 ppm (10 ng cm-2). This approach provides significant advancements in the fabrication of nanogaps and enhanced spectroscopy, offering substantial implications for future research and applications.