Preparation of a high-performance thermally shrinkable polystyrene SERS substrate via Au@Ag nanorods self-assembled to detect pesticide residues

This paper reports a “bottom-up” substrate preparation method using a two-phase interface self-assembly technology that combines silver-coated gold core–shell nanorods with the thermally shrinkable polystyrene (TSP) support material for surface-enhanced Raman spectroscopy (SERS), that is, TSP-SERS substrate. The gold nanorods with long absorption wavelength were used as the core, and the silver shells were coated to obtain the core–shell nanostructures with a stronger resonance with the wavelength of the light source. The density of the nanostructures and numbers of “hot spots” within the light spot increased via the three-dimensional folding feature formed by thermal shrinkage. The combined effect of the two factors increases the enhancement factor by an order of magnitude to 10 7 after thermal contraction. The detection concentration of 4-mercaptobenzoic acid can reach 10 −9 M, and the maximum relative standard deviation is only 8.9%. In fact, the detection limit of benzimidazole on the surface of apple can reach 0.5 mg/L, and the recovery deviation is controlled within the range of 11.7%. The practical detection of benzimidazole pesticide residues showed that this method has wide application prospects in the detection of pesticide residues.