Synthesis of a superparamagnetic MFNs@SiO₂@Ag ₄SiW₁₂O₄₀/Ag composite photocatalyst, its superior photocatalytic performance under visible light illumination, and its easy magnetic separation

A novel superparamagnetic Ag@silver-based salt photocatalyst, MFNs@SiO ₂@Ag₄SiW₁₂O₄₀/Ag, was created, which demonstrated highly efficient photocatalytic performance under visible light illumination in both the degradation of methylene blue (MB) and the disinfection of Escherichia coli (E. coli) bacteria. In this composite photocatalyst, well-dispersed, superparamagnetic magnesium ferrite nanoparticles (MFNs) were used as the core because of their easy magnetic separation capability. A passive SiO₂ mid-layer was used to separate MFNs and Ag₄SiW ₁₂O₄₀ and form a strong bond with silver ions for their loading after -SH surface modification. The Ag₄SiW₁₂O ₄₀ layer was subsequently formed by the reaction with silicotungstic acid to avoid the commonly adopted calcination procedure after deposition/precipitation, and silver nanoparticles were formed on the surface of Ag₄SiW₁₂O₄₀ layer after UV irradiation to further enhance their photocatalytic performance and stability under visible light illumination. The surface modification on the passive SiO₂ mid-layer and the bridging procedure for material loading developed in our approach could be readily applied to other material systems for the creation of novel composite materials with various functions.