A low-cost flexible SERS sensor based on bimetallic Au@AgNCs for sensitive in-situ detection of thiabendazole residues on apple

Background Rapid screening of pesticide residues directly on fruit surfaces is essential for food safety monitoring. However, conventional analytical methods usually require complicated sample pretreatment. This limitation restricts their practical use in in-situ residue analysis. Moreover, the non-planar morphology of fruit surfaces requires sensing platforms with good conformability. Results In this study, a low-cost flexible surface-enhanced Raman scattering (SERS) sensor was developed for thiabendazole (TBZ) residue detection on apple. Bimetallic Au@Ag core-shell nanocubes (Au@AgNCs) were immobilized onto inexpensive cellulose filter paper (CFP) through a simple polyelectrolyte-mediated layer-by-layer self-assembly strategy. The sharp corners of Au@AgNCs provided abundant plasmonic hotspots and strong Raman enhancement. The polyelectrolyte layers improved nanoparticle loading uniformity and substrate stability. The optimized sensor achieved an enhancement factor of 5.72 × 10 5 and showed good signal reproducibility. For in-situ detection of TBZ residues on apple, the sensor exhibited a linear response over 0.5–50 mg/L, with a correlation coefficient of 0.993 and a detection limit of 0.30 mg/L. The quantitative results were further validated by high-performance liquid chromatography (HPLC), confirming the reliability of the proposed sensor for real-sample analysis. Significance and novelty Overall, the Au@AgNCs/CFP/PSS flexible SERS sensor provides a low-cost and sensitive platform for in-situ detection of pesticide residues on irregular fruit samples.