Clean and reproducible SERS substrates for high sensitive detection by solid phase synthesis and fabrication of Ag-coated Fe _3O _4 microspheres

摘要

The solid-phase synthesis of Ag-coated Fe _3O _4 microsphere was elaborated under argon atmosphere. This straightforward process utilized neither reducing agents nor electric current and involved the dry mixing of a precursor of CH _3COOAg with Fe _3O _4 microspheres followed by heating in an inert atmosphere. Ag nanoparticles with diameters of 30-50 nm were well-decorated on the surfaces of Fe _3O _4 microspheres. The as-synthesized Ag-coated Fe _3O _4 microspheres were assembled into a surface-enhanced Raman scattering (SERS) substrate holding clean and reproducible properties under an externally exerted magnetic force. Using these nanoprobes, analyte molecules can be easily captured, magnetically concentrated, and analyzed by SERS. This clean SERS substrate was used to detect 4-aminothiophenol, even at a concentration as low as1.0 × 10 ~(-12) M. In particular, the Ag-coated Fe _3O _4 microspheres, acting as reproducible SERS substrates, were applied to detect methyl-parathion and 4-mercaptopyridine. Strong SERS signals were obtained with the analytes at a concentration of 1.0 × 10 ~(-6) M. The unique, clean, and reproducible properties indicate a new route in eliminating the single-use problem of traditional SERS substrates and show promising applications for detecting other organic pollutants. Similarly, this work may provide a new model system to a series of metal-Fe _3O _4 decorating reactions for a reproducible utilization.