An integrated "Sampling-SERS detection-regeneration" analytical platform based on flexible Ag/AgCl/CdS heterojunctions for pesticide monitoring

Surface-enhanced Raman scattering (SERS) has emerged as a powerful tool for the rapid detection of pesticide residues. As the demand for rapid on-site screening of agricultural products continues to rise, traditional SERS approaches that rely on rigid substrates and cumbersome pretreatment steps struggle to meet the diverse requirements of practical field testing. Therefore, achieving a seamless transition from direct on-site sampling to highly sensitive and accurate quantitative analysis remains a critical challenge.

An integrated analytical platform was developed by constructing a noble-metal/semiconductor Ag/AgCl/CdS (AASC) heterojunction on a flexible carbon cloth substrate. The substrate's flexibility ensures conformal contact with irregular surfaces for rapid in situ sampling. Driven by the synergy between the electromagnetic enhancement of localized surface plasmon resonance (LSPR) from Ag nanoparticles (Ag NPs) and the charge-transfer (CT) mechanism within the Z-scheme heterojunction, the AASC substrate exhibits exceptional SERS sensitivity, achieving a limit of detection (LOD) of 6.46 × 10^-11 M for 4-mercaptobenzoic acid (4-MBA). The integrated semiconductor components also impart photocatalytic activity, yielding an 83.64% degradation efficiency for malachite green (MG) within 90 min. For practical applications, the AASC platform enables swabbing-based in-situ screening of thiram (TRM) and thiabendazole (TBZ) residues on real fruit surfaces, achieving surface LODs of 0.096 and 0.805 ng/cm², respectively.

While inherently focused on surface-level contaminants rather than deeply penetrating systemic pesticides, this rapid swabbing strategy excels as a highly efficient and non-destructive frontline screening tool. The method demonstrates excellent quantitative reliability and supports alternating cyclic detection of different pesticides, followed by efficient substrate regeneration through photocatalytic degradation. This integrated "sampling-SERS detection-regeneration" strategy provides a sustainable and reliable solution for on-site pesticide monitoring and environmental safety analysis.