Seed-mediated synthesis of high-performance silver-coated magnetic nanoparticles and their use as effective SERS substrates

A novel seed-mediated strategy was employed to synthesize high-performance silver-coated magnetic nanoparticles (Fe₃O₄@SiO₂@Ag MNPs). Ag seeds were produced on an inner SiO₂ shell with an electroless plating method. These seeds served as nucleation sites for the growth of the outer Ag shells. The morphological characteristics of the Ag shells were shown to be easily controlled by varying the concentration of AgNO₃. Moreover, the shell-coating process was completed within a few seconds and the resulting product was highly uniform in size and shape with monodispersity and good magnetic responsivity. Considering the synergistic effect of the target enrichment property and interparticle hotspots created by magnetism-induced aggregation, we propose that the Fe₃O₄@SiO₂@Ag MNPs could function as a versatile Surface-enhanced Raman scattering (SERS) substrate. The SERS ability was verified by detecting the Raman probe 4-aminothiophenol (PATP) and pesticide thiram with detection limits of as low as 10⁻¹¹ M and 10⁻⁹ M, respectively. The simple process and high sensitivity make the Fe₃O₄@SiO₂@Ag MNP a promising tool for SERS detection.