Investigation on the formation, structural and photocatalytic properties of mixed Mn-Zn ferrites nanoparticles embedded in SiO2 matrix

The structure, morphology and photocatalytic features of the Mn-Zn ferrite nanoparticles embedded in SiO2 matrix produced by a modified sol-gel synthesis were investigated. The synthesis consists of mixing the metal nitrates, 1,4-butanediol and tetraethylorthosilicate, formation of the SiO2 matrix by gelation, formation of the metallic succinate precursors by heating the gel up to 200 degrees C and formation of the ferrite system by thermal treatment at higher temperatures. The formation of Mn-, Zn- and Fe-succinate precursors up to 200 degrees C and their decomposition into ferrites up to 400 degrees C was confirmed both by thermal analysis and Fourier-transform infrared spectroscopy. The X-ray diffraction provided information on the crystalline phases, crystallite size and lattice constant, while the morphology of the samples was investigated by transmission electron microscopy. The crystallite size increased (30.5-53.4 nm), while the energy band gap of the samples decreased (2.09-1.33 eV) with the increase of the Mn content in the ferrite; thus, the amount of manganese nitrate used in the synthesis could be an easy tailoring approach of the mixed Mn-Zn ferrites. All samples showed sonophotocatalytic activity, being able to degrade Rhodamine B under visible light irradiation, Mn0.3Zn0.7Fe2O4@SiO2 sample having the best sonophotocatalytic performance.