Fluorophore-assisted synthesis of silver flowers on copper-patterned flexible substrates for SERS detection of thiram residues on apples

A rapid and non-destructive Surface-Enhanced Raman Spectroscopy (SERS) approach using silver flowers (AgFws) as a substrate was successfully developed for the detection of trace amounts of thiram, a dithiocarbamate fungicide. In this study, we report the facile preparation of AgFws on a copper-coated polyethylene terephthalate (PET) substrate utilizing a “complexation-triggered crystallization” phenomenon. The 2,5-di(pyridin-4-yl)thiazolo[5,4-d]thiazole (Py₂TTz) dye serves as both a reducing agent and a nucleation site for the crystallization of silver ions, forming AgFws on the copper layer, thereby yielding a flexible SERS substrate. The copper coating enhances the formation of AgFws due to the excellent adsorption properties of the Py₂TTz dye. The high surface area-to-volume ratio of the AgFws enables sensitive detection of food contaminants. The developed SERS substrate successfully identified trace amounts of thiram residues on apple peel with a detection limit of 1 pg/cm² and in solutions with a concentration as low as 10⁻¹⁴ M.