Synthesis of a superparamagnetic MFNs@SiO2@Ag4SiW12O40/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@SiO2@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 Ag4SiW12O40 and form a strong bond with silver ions for their loading after -SH surface modification. The Ag4SiW12O40 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.