Hovenia acerba-inspired silver nanostructure-modified hydrogel SERS substrate with 3D high-density network hotspots for thiram detection on various fruit surfaces.

The detection performance of surface-enhanced Raman scattering (SERS) substrates is closely related to their three-dimensional plasmonic nanostructures. In this work, a series of three-dimensional porous hovenia acerba-like silver nanostructure-decorated polyvinyl alcohol hydrogel (HA-AgNPs@PVA) SERS substrates were fabricated by a facile in-situ chemical reduction strategy. Three-dimensional porous plasmonic nanostructures possess numerous nanopores, capable of forming multi-level and high-density hot spots. Additionally, the porous nanostructures can accommodate a greater number of probe molecules, significantly enhancing SERS performance. Using crystal violet as probe molecule, the optimized HA-AgNPs@PVA SERS substrate achieves a detection sensitivity of 10-10 M and an enhancement factor of 1.6 × 108. Moreover, flexible HA-AgNPs@PVA SERS substrate was applied for the detection of thiram on various fruit surfaces using a "stick-and-read" approach, delivering a high detection sensitivity of 10-8 M and demonstrating excellent quantitative detection capability. The developed flexible SERS platform exhibits great potential for on-site food safety monitoring.