Fe3O4@SiO2@TiO2@Pt Hierarchical Core–Shell Microspheres: Controlled Synthesis, Enhanced Degradation System, and Rapid Magnetic Separation to Recycle

Magnetic composite microspheres consisting of a SiO2-coated Fe3O4 core, an ordered TiO2 hierarchically structured shell, and a Pt nanoparticle layer dispersed on the surface of the TiO2 nanoplatelets have been successfully synthesized using a facile and efficient method. The shells of TiO2 hierarchical microspheres were assembled from nanoplatelets, which exposed the high-energy {001} facets, and the Pt nanoparticles were evenly deposited on the surface of the TiO2 nanoplatelets, with a concentration of ∼1 wt %. The resulting composite microspheres exhibited flower-like hierarchical structures with a 202.42 m2 g–1 surface area and possessed superparamagnetic properties with a high saturation magnetization of 31.5 emu g–1. These features endow the obtained composite microspheres with a high adsorption capacity and strong magnetic responsivity that could be easily separated by an external magnetic field. The high photocatalytic activity toward Rhodamine B (RhB) degradation may be caused by the hierarchically structured TiO2 with exposed high-energy {001} facets and the Pt nanoparticle deposits on TiO2 surfaces, which would be efficient for the electron transfer reactions. In addition, the composite microspheres showed high recycling efficiency and stability over several separation cycles.