SERS-Active Composites with Au-Ag Janus Nanoparticles/Perovskite in Immunoassays for Staphylococcus aureus Enterotoxins.

The accurate detection of enterotoxins (SEs) is vital for food safety owing to their high pathogenicity, which may be performed with surface-enhanced Raman scattering (SERS) if SERS-active nanostructures are used. Herein, a Au-Ag Janus nanoparticle (NPs)/perovskite composite-engineered SERS immunoassay was developed for SEC detection. Plasmonic Au-Ag Janus NPs demonstrated inherent SERS activity from the 2-mercaptobenzoimidazole-5-carboxylic acid ligands. CsPbBr@mesoporous silica nanomaterials (MSNs) were prepared and transformed into CsPbBr@MSNs in the aqueous phase. Paired SEC antibody-antigen-driven plasmonic Au-Ag Janus NP-CsPbBr@MSN composites were prepared. They showed amplified SERS activity, attributed to the depressed plasmonic decay due to electromagnetic field enhancement and the electron transfer mechanism. A positive relationship was established between SERS signals of composites and the SEC concentration. An additive-free SERS immunoassay was developed for simple, sensitive, and reproducible SEC detection. This study will be extended to develop multiple additive-free SERS-active plasmonic NP/perovskite composites that will open up the possibility of exploring more SERS detection probes for food safety monitoring.