Magnetic Fe₃O₄@SiO₂@Ag@COOH NPs/Au Film with Hybrid Localized Surface Plasmon/Surface Plasmon Polariton Modes for Surface-Enhanced Raman Scattering Detection of Thiabendazole.

A magnetic Fe₃O₄@SiO₂@Ag@COOH nanoparticle (NPs)/Au film was fabricated as an effective surface-enhanced Raman scattering (SERS) substrate through a combination of a solvothermal reaction, the Stöber method and an in-situ reaction. The superparamagnetic property of Fe₃O₄@SiO₂@Ag and the decoration with -COOH groups allow efficient enrichment and capture of thiabendazole molecules. A large quantity of sub-10 nm gaps emerge when Ag NPs are decorated on the surface of the SiO₂ shell, offering a dramatic electromagnetic field enhancement induced by localized surface plasmon resonance (LSPR). Finite-difference time-domain (FDTD) simulations show that strong near-field enhancement around the gap areas between the Ag NPs and Au film occurs, which is caused by the coupling between the LSPR of the Ag NPs and surface plasmon polaritons (SPPs) of the Au film. Due to the superparamagnetic property and high electromagnetic field enhancement, the Fe₃O₄@SiO₂@Ag@COOH NPs/Au film as a SERS substrate can detect 1 μg/L thiabendazole in solution, showing great potential for SERS detection of environmental pollutants.