A SERS sensor of Au/Ag nanoparticles grown on the surface of ZnO/PPy@PEDOT: PSS film for detecting norfloxacin residues in milk.

A surface-enhanced Raman scattering (SERS) sensor of Au/Ag nanoparticles (NPs) grown on ZnO/polypyrrole@Poly(3,4-ethylene dioxythiophene)-poly(styrene sulfonate) (PPy@PEDOT:PSS) film for detecting norfloxacin (NFX) residues in milk is presented. The ZnO/PPy@PEDOT:PSS film was prepared by the electrochemical deposition method. Subsequently, Ag NPs and Au NPs were deposited on the surface of ZnO/PPy@PEDOT:PSS film to form a Au/Ag/ZnO/PPy@PEDOT:PSS film by an electrochemical deposition process and the magnetron sputtering process, respectively. Owing to the charge transfer between the SERS substrate and the NFX molecules, this SERS sensor could effectively identify low-concentration NFX molecules with a limit of detection (LOD) of 0.84 nM. Moreover, it could also recognize NFX residues in milk with recoveries of 91.2% to 108.4%. The SERS sensor of Au/Ag/ZnO/PPy@PEDOT:PSS film had a high sensitivity, excellent long-term stability, and significant potential in food safety monitoring applications.