Ultrasensitive Detection of Pesticide Residues on Apple Surfaces with a Cavity-Enhanced Stick-Peel Sensing Platform

The extensive overuse of pesticides around the world has made the adoption of low-cost, easy, and versatile detection techniques even more crucial for ensuring food safety. Consequently, surface-enhanced Raman scattering (SERS) has garnered recent attention as a rapid, economical, and noninvasive approach for pesticide detection. In this study, we propose an ultrasensitive SERS platform for the detection of chlorpyrifos and carbendazim on apple surfaces. This platform utilizes the stick-peel principle, facilitating rapid, straightforward, and noninvasive pesticide detection without the need for labeling. The Raman signal is enhanced by two phenomena. First, there are the localized surface plasmons of Ag nanoparticles on a flexible polydimethylsiloxane (PDMS) support. Second, there is a separate reusable Ag mirror substrate with a quarter-wave spacer that generates constructive optical interference. The efficacy of this approach is substantiated by the corroboration from optical simulations, which validate the observed field enhancement and facilitate the optimization of the morphology. The optimized structure of the platform exhibits limits of detection as low as 0.004 ng/cm² and 2.16 ng/cm² for chlorpyrifos and carbendazim, respectively. These limits are considerably lower than the limits established by international regulatory bodies for these particular pesticides. The combination of high sensitivity and ease of use, in conjunction with the cost-effectiveness of lithography-free substrate fabrication, suggests promising potential for the commercialization of such platforms within the food safety industry.