Regulating the silica shell thickness of magnetic nanoparticles to enhance surface fluorescence enhancement properties.

Surface-enhanced fluorescence (SEF) and surface-enhanced Raman scattering (SERS) technologies are widely used in high-sensitivity detection but are limited by the susceptibility of noble metal nanoparticles to oxidation and agglomeration, as well as fluorescence quenching. In this paper, Fe3O4@SiO2@Ag@SiO2 core-shell magnetic nanoparticles with tunable outer SiO2 thickness were synthesized by adjusting the dosage of tetraethyl orthosilicate (TEOS). Fe3O4 endows them with superparamagnetic, Ag NPs enhances signals via the localized surface plasmon resonance (LSPR) effect, and the SiO2 shell inhibits oxidation and regulates the distance between molecules and metals. Performance tests show that Fe3O4@SiO2@Ag@SiO2-35 exhibits the optimal SEF performance with an enhancement factor of 7.37, along with good stability and recyclability. Fe3O4@SiO2@Ag@SiO2-25 achieves significant SERS enhancement for Rhodamine 6G (R6G) with excellent signal uniformity (RSD ≤ 6.8%). These multifunctional nanoparticles provide a novel material for the highly sensitive detection of environmental pollutants and hold great value in the field of environmental safety monitoring.