SERS-Based Detection\nof Thiram in Apple Peel Samples\nUsing Thiomalic Acid-Ag/Au Nanoparticles

This study employs a seed-mediated growth method alongside\ngalvanic\nreplacement to synthesize thiomalic acid-silver/gold nanoparticles\n(TMA-Ag/AuNPs), with precise control over the morphology of the TMA-Ag/AuNPs\nachieved by adjusting the volume ratios of TMA-AgNPs to Au<sup>3+</sup>, which alters the rates of chemical reduction and galvanic replacement.\nIn the exploration of surface-enhanced Raman scattering (SERS), Ag\ndendritic structures were electroplated onto FTO substrates to fabricate\nAgFTO substrates, which, when combined with TMA-Ag/AuNPs, exhibit\nenhanced Raman signals due to optimal particle size and increased\nsurface roughness, facilitating significant adsorption of Raman probe\nmolecules. This integration results in a SERS enhancement factor of\n5.8 × 10<sup>6</sup>. Specifically focusing on the thiram detection,\nthe TMA-Ag/AuNPs demonstrate a strong affinity for sulfur components\nof thiram, promoting the cleavage of the S–S bond to form dimethylthiocarbamates,\nthereby amplifying the Raman signal. Under optimized conditions, the\nproposed method exhibits a linear detection range from 0.005 to 0.1\nppm, a coefficient of determination of 0.984, and a detection limit\nof 0.258 ppb. The method applied to fruit peel analysis showed a 93–109%\nrecovery rate with a relative standard deviation of less than 5.95%.\nThe developed TMA-Ag/AuNPs-AgFTO substrate showcases simplicity in\npreparation, excellent selectivity, and high sensitivity, successfully\ndetecting thiram in real samples and offering a promising approach\nfor enhancing food safety.