Dialdehyde starch-enclosed silver nanoparticles substrate with controlled-release “hotspots” for ultrasensitive SERS detection of thiabendazole

[Display omitted] •In this study, we proposed a novel strategy the concept of controlled-release hotspots. On the one hand, Ag NPs were encapsulated in the dialdehyde starch granules to prevent oxidation and aggregation, which effectively prolongs the storing period time of the substrate. On the other hand, Ag NPs were released from dialdehyde starch granules, and abundant hotspots were generated at the same. Therefore, the as-prepared substrate can achieve high stability and sensitivity by means of controlled-release hotspots.•In particular, a flexible paper-based substrate based on Ag@CDS was also fabricated and successfully applied to detect the TBZ residues on the surface of the apple by simply wiping sampling. Pesticide residues have long been a major concern for food safety. In this study, a dialdehyde starch-encapsulated silver nanoparticles composite with controlled-release “hotspots” was developed as a surface-enhanced Raman scattering (SERS) substrate. At room temperature, most of the Ag NPs were encapsulated in dialdehyde starch, which is beneficial for improving stability, and when heated to the gelatinization point, Ag NPs are completely released and abundant hot spots are formed. We demonstrated sensitive detection of thiabendazole (TBZ) in or on the surface of an apple by means of two ways, i.e., detecting the analyte in solution after pretreatment and in-situ detecting the analyte by using a flexible paper-based substrate. The results showed that the detection limits of TBZ by the two ways were 0.052 ppm and 0.051 ppm respectively, and the recoveries of TBZ range from 96.80 % to 105.46 %. Overall, this SERS substrate shows great potential for pesticide residue detection in food.