Liquid–Liquid Interfacial Self-Assembly of Au-Ag Nanoparticles for High-Performance SERS Detection of Thiram in Environmental Water Samples

Gold and silver nanoparticles have attracted extensive attention in SERS detection due to their excellent plasmonic properties. In this study, a high-performance SERS substrate was successfully prepared by a liquid–liquid self-assembly strategy. Driven by the Marangoni effect, Au-Ag nanoparticles spontaneously form a uniform and dense monolayer structure on the silicon wafer, constructing an efficient plasmon ”hotspot” region, which significantly improves the detection sensitivity of the substrate. The performance of the SERS substrate was systematically evaluated using CV and Me B as Raman probe molecules. The results show that the substrate exhibits an excellent enhancement effect and good SERS sensitivity for both probe molecules. The characteristic vibration peak can be clearly identified, and the detection limit (LOD) of crystal violet is 6.76 × 10−11 M. The substrate was applied to detect thiram residues in lake water with a LOD of 1.084 × 10−7 M, achieving highly sensitive detection. This study shows that Au-Ag nanoparticles deposited on silicon wafers by liquid–liquid self-assembly strategy can be used as a high-performance SERS substrate. It can be used for rapid and sensitive detection of thiram pesticide residues in water, and provides an efficient and feasible analysis tool for water environment safety monitoring.