Detection of pesticide residue using an Fe ₃ O ₄ /GO/Ag nanocomposite as a SERS substrate and mechanism investigation

Considering that pesticide residues cause significant harm to health and the environment, it is crucial and urgent to fabricate surface-enhanced Raman scattering (SERS) substrates with high sensitivity to detect pesticide residues. In this study, a three-layer structure of multifunctional Fe₃O₄/GO/Ag nanoparticles (NPs) as an active substrate for SERS was fabricated and comprehensively characterized through X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), elemental mapping, and X-ray photoelectron spectroscopy (XPS). The active substrate was used to detect thiram pesticide through SERS. Combined with the synergistic effect, Ag NPs and graphene oxide (GO) possessed high-density and ordered hot spots to enhance the electromagnetic field; therefore, signal amplification and fascinating sensitivity were achieved. The lowest concentration of thiram for clear presentation of the peak was 10^-12 mol L^-1. There was a satisfactory linear relationship, ranging from 10^-10 to 10^-4 mol L^-1, with a low limit of detection, high sensitivity, satisfactory enhancement factor (EF), stability, and repeatability. In addition, Fe₃O₄/GO/Ag was successfully applied to identify pesticide residues in a practical sample. Furthermore, the enhancement mechanism, including electromagnetic enhancement and chemical reinforcement, is discussed in detail. Fe₃O₄/GO/Ag is a potential active substrate for SERS and can be applied for rapid detection in the food industry, environmental fields and biomedicine with fascinating sensitivity.