Graphene oxide-based three-dimensional Au nanofilm with high-density and controllable hotspots: A powerful film-type SERS tag for immunochromatographic analysis of multiple mycotoxins in complex samples

Co-contamination of mycotoxins in food and environment is a common phenomenon, which easily causes cumulative and synergistic damaging effects to human and animal health, poses great health and economy burdens to the world. A convenient technology for detection of multiple and low-concentration mycotoxins in real samples is highly desired but remains a challenge. Here, we proposed a multiplexed surface-enhanced Raman scattering (SERS)-immunochromatographic assay (ICA) that can sensitively and simultaneously detect three mycotoxins in unprocessed complex samples, using a graphene oxide-based three-dimensional (3D) Au nanofilm (called GO@Au-Au) as the film-type SERS tag. A precise sub-1 nm PEI layer was constructed into the GO@Au-Au nanostructure as built-in nanogap, which can accommodate Raman reporter molecules and create stable hotspots between the inner GO@Au film and outer assembled AuNP satellites. Grafting the 30 nm AuNPs onto the 2D GO@Au nanofilm greatly improved the SERS activity and colorimetric signal of film-type tags. Compared with traditional spherical SERS tags, the film-type GO@Au-Au can provide greater reaction interface, excellent stability and dispersibility and multiple SERS hotspots over large area for ICA using. Given these advantages, the proposed SERS-ICA can achieve simultaneous quantitative detection of fumonisin B1, aflatoxin B1, and zearalenone, with low detection limit (0.529, 0.745, and 5.90 pg mL⁻¹), short testing time (20 min), and high accuracy for real food/experimental samples. Our method shows great potential to fulfill practical requirements for detection of multiple mycotoxins.