Gelatin‑silver nanocube composite hydrogel SERS substrate for sensitive detection of thiram.

Surface-enhanced Raman scattering (SERS) is a powerful tool for rapid on-site detection of pesticide residues, but its performance heavily relies on the substrate. Herein, a gelatin‑silver nanocube (Ag NC) composite hydrogel SERS substrate was developed via mild EDC-NHS crosslinking coupled with low-temperature gelation. The three-dimensional porous hydrogel efficiently enriches target molecules, while the sharp edges of Ag NCs generate abundant electromagnetic hotspots. Using rhodamine 6G as a probe, the optimized substrate (20% gelatin, Ag NC/gelatin volume ratio 3:1) exhibited good uniformity, reproducibility, and stability. For thiram detection, a linear response was obtained from 10-4 to 10-7 M with a limit of detection (LOD) of 4.45 × 10-8 M in standard solution. Practical applicability was demonstrated in orange juice, where thiram was detected down to 1.0 × 10-6 M (LOD = 4.78 × 10-7 M) with recoveries of 96.9-97.9%. This work provides a gelatin-based, stable and sensitive SERS platform for food safety monitoring.