Generalized green synthesis of Fe3O4/Ag composites with excellent SERS activity and their application in fungicide detection

This paper reports the generalized green synthesis of a series of Fe3O4/Ag composites by magnetron sputtering method. The amounts of silver nanoparticles located on the hollow Fe3O4 magnetic nanoparticles can be tuned by controlling the sputtering time. The surfaces of Fe3O4/Ag composites are rough with high density and numerous Ag nanogaps (which can serve as Raman active hot spots to amplify the Raman signal), providing the sound reliability and reproducibility of Raman detection. With p-aminothiophenol and Rhodamine 6G (R6G) for probe molecules, the surface-enhanced Raman scattering (SERS) properties of these Fe3O4/Ag composites were studied. It was found that the SERS signal reached the maximum with the sputtering time of 130 s, indicating that this compound had most hot spots. In this paper, we used the composite with the strongest SERS signal for thiram detection, and the detection limit can reach 5 × 10−7 mol/L (about 0.012 ppm), which is lower than the maximal residue limit of 7 ppm in fruit prescribed by the U.S. Environmental Protection Agency. The Fe3O4/Ag composites are readily available, easy to carry, and show great potential for applications in universal SERS substrates in practical SERS detection.