CoFe2O4@SiO2@TiO2 core-shell nanoparticles for photocatalytic water decontamination

Abstract

In the present work is reported, following a facile process, the synthesis of cobalt ferrite nanoparticles covered with a shell of SiO2, and then, covered with a shell of TiO2. In the first step, cobalt ferrite nanoparticles were prepared by coprecipitation of Co+2 and Fe +2 ions in basic medium, followed by a simple controlled oxidation process carried out by nitrate ions in basic medium with inert atmosphere at 95°C for 24h. In the second step, SiO2 particles were deposited by heterogeneous nucleation onto the surface of the ferrite in alcohol medium by alkalinization of tetraethylortosilane solutions, finally, in the third step, the TiO2 shell film is deposited by using sol-gel technique. Characterization techniques were performed to determine the particle morphology and size distribution (Scanning electron microscopy), crystalline structure (X-ray diffraction). Results showed that cobalt ferrite nanoparticles can be obtained following this synthesis route without using surfactants as size drivers, which is a common reagent in nanoparticle preparation, giving a size distribution of 162 ± 30 nm and a polyhedral geometry. Also, it was observed that SiO2 is homogeneously distributed onto the surface of the cobalt ferrite, and that TiO2 shell films covered well, creating a catalyst that also presents magnetic response. This kind of catalyst nanomaterial, presents a magnetic response, and is a stable and environmentally safe, then could be separated easily from the aqueous medium at the end of the purification process by applying an external magnetic field.