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 SiO 2 -coated Fe 3 O 4 core, an ordered TiO 2 hierarchically structured shell, and a Pt nanoparticle layer dispersed on the surface of the TiO 2 nanoplatelets have been successfully synthesized using a facile and efficient method. The shells of TiO 2 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 TiO 2 nanoplatelets, with a concentration of ∼1 wt %. The resulting composite microspheres exhibited flower-like hierarchical structures with a 202.42 m 2 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 TiO 2 with exposed high-energy {001} facets and the Pt nanoparticle deposits on TiO 2 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.