Simple and rapid capillarity-assisted ultra-trace detection of thiram on apple surface with a silver nanoparticles/filter paper SERS substrate

Thiram is a readily synthesized, cost-effective antimicrobial agent widely used to control diseases in fruits and vegetables. Given the potential health hazards associated with thiram residues and advancements in detection methods, it is crucial to develop a rapid and sensitive technique for detecting these residues on fruit surfaces. Here, we prepared the Ag@filter paper (Ag@FP) surface-enhanced Raman scattering (SERS) substrate in a controlled manner and innovatively developed a capillarity-assisted SERS (CA-SERS) detection method. Sampling can be completed in less than 1 min by either wiping or using the CA-SERS method. Utilizing a portable Raman device, the detection limit for thiram residues on apple surfaces can reach as low as 0.005 ng/cm² with the CA-SERS detection method. Furthermore, the substrate is cost-effective, can be prepared in just 7 min, and remains stable at room temperature for up to 40 days. Additionally, we developed a cost-effective, centimeter-scale auxiliary detection device to facilitate efficient on-site detection.