A mild synthetic route to Fe3O4@TiO2-Au composites: preparation, characterization and photocatalytic activity

Abstract To prevent and avoid magnetic loss caused by magnetite core phase transitions involved in high-temperature crystallization of sol-gel TiO 2 , a direct and feasible low-temperature crystallization technique was developed to deposit anatase TiO 2 nanoparticle shell on Fe 3 O 4 sphere cores. To promote the photocatalytic efficiency of the obtained core-shell Fe 3 O 4 @TiO 2 magnetic photocatalyst, uniformly distributed Au nanoparticles (NPs) were successfully immobilized on the core-shell Fe 3 O 4 @TiO 2 spheres via a seed-mediated growth procedure. The 3 nm Au colloid absorbed on Fe 3 O 4 @TiO 2 served as a nucleation site for the growth of Au NPs overlayer. The morphology, structure, composition and magnetism of the resulting composites were characterized, and their photocatalytic activities were also evaluated. In comparison to Fe 3 O 4 @TiO 2 , Fe 3 O 4 @TiO 2 -Au exhibited higher photocatalytic activity for organic degradation under UV irradiation. This enhanced mechanism may have resulted from efficient charge separation of photogenerated electrons and holes due to the Au NPs attached on the TiO 2 . In addition, the composites possessed superparamagnetic properties with a high saturation magnetization of 44.6 emu g −1 and could be easily separated and recycled by a magnet.