Reusable SERS substrates based on flexible polyamide supports with hierarchical structures for in-situ detection of pesticide residues

Abstract

Performance optimization and functionality expansion of surface-enhanced Raman scattering (SERS) substrates are the main challenges towards their practical applications. Targeting the urgent need for rapid detection of trace pesticide residues in food safety monitoring, a reusable and highly sensitive SERS substrate based on soft polyamide (PA) fabric was developed. Dense ripple-like nanostructures, proven to significantly enhance SERS performance, were successfully created on the interwoven PA fibers through oxygen plasma (OP) treatment. Followed by thermal deposition of Ag, the optimal Ag-35/PA-20 substrate exhibited an EF of 1.28 × 10⁸ and satisfactory uniformity. The substrate's real-world detection capability was demonstrated by in-situ detection of 0.1 ppm thiram, a concentration much lower than the U.S. regulatory limit, on apple surfaces by a swabbing method. Beyond generating nanostructures, OP treatment simultaneously modified the PA surface chemistry, as confirmed by FTIR and XPS analyses. The introduction of strongly polar groups not only altered the Ag growth mode, but also ensured the robust adhesion between Ag and PA surface, as verified by peel-off tests. Owing to its excellent mechanical stability, the substrate demonstrated superior reusability, maintaining high activity even after five reuse cycles. This cost-effective, flexible substrate combines high sensitivity with excellent reusability, creating new opportunities for SERS-based rapid food safety monitoring.