SERS-enabled rapid detection of difenoconazole residues in tomatoes for food safety applications

Tomatoes are consumed worldwide at high volume, and difenoconazole (DFZ) is extensively applied to protect tomato crops from fungal diseases, making DFZ residue a growing food-safety concern. Surface-enhanced Raman scattering (SERS) provides a rapid and ultrasensitive approach for pesticide monitoring, but most DFZ-related studies rely solely on noble-metal electromagnetic enhancement. Integrating metals with semiconductors capable of strong charge-transfer interaction can unlock additional chemical enhancement, significantly improving low-level detection. In this work, an Ag nanoparticle-decorated α-Fe₂O₃ nanorod SERS substrate (Ag NPs/α-Fe₂O₃ NRs) is developed for rapid DFZ detection. This structure provides abundant active sites and synergistically integrates electromagnetic and chemical enhancement, enabling strong Raman signals at trace levels. The developed substrate achieves detection limits of 9.5 × 10^-9 M for standard DFZ solutions and 32 μg/kg for tomato samples. The direct-growth design also improves signal uniformity and reproducibility compared with powder-based substrates. These results demonstrate that the Ag NPs/α-Fe₂O₃ nanorod SERS substrate offers a rapid, sensitive, and reliable tool for monitoring DFZ residues in tomatoes and ensuring agricultural food safety.