Facile Method to Fabricate Cactus-like Ag NPs/CuO/Cu₂O Nanocomposites for Recyclable SERS Detection of Trace Carbendazim Residues

Detection of trace carbendazim in agricultural products or environment is challenging but important for human health and environmental protection. Developing a sensitive and recyclable surface-enhanced Raman scattering (SERS) substrate is one of the effective methods to detect such pesticide residues. In this work, we developed a facile method to fabricate a three-dimensional cactus-like Ag nanoparticles/CuO/Cu2O nanocomposite (CACN) based on a galvanic replacement reaction between Tollens' reagent and Cu foam. This design combined the Raman enhancement effect and photocatalytic activity, providing a multifunctional and reusable substrate for highly sensitive SERS detection. It was found that the enhancement and photocatalysis of the CACN substrate were closely related to the concentration of Tollens' reagent, and the 10-CACN substrate (prepared at 10 mM) demonstrated excellent sensitivity, reproducibility, and recyclability. The substrate was successfully applied for the detection of carbendazim solution with a detection limit of 1.5 × 10-10 M and could be reused up to 7 times. More importantly, the substrate can be employed for the detection of trace carbendazim in real apple peels with a detection limit of ∼8.5 × 10-4 ppm, which is far below that of 2.0 × 10-1 ppm suggested by China, United Kingdom, and European Union. These results suggest that the facile fabrication method and the excellent substrate would facilitate the SERS technology closer to practical application in the detection of pesticide residues.