Synthesis, characterization of Fe3O4@SiO2@ZnO composite with a core-shell structure and evaluation of its photocatalytic activity

The Fe3O4, Fe3O4@SiO2, and Fe3O4@SiO2@ZnO composites that can be magnetically separated were synthesized using hydrothermal and sol-gel methods. SEM-EDS, ICP-AES, TEM, XRD, FT-IR, UV–vis, VSM, and XPS analyzes were used for the characterization of the composites. With TEM and SEM results, it has been determined that the average diameters of the Fe3O4, Fe3O4@SiO2, and Fe3O4@SiO2@ZnO composites are 210, 220 and 230 nm, respectively, and the composites have a spherical structure and homogeneous distribution. The weight percentage of the composites were determined by the ICP-AES analysis. The XRD analysis determined that the crystal structures of the composites are compatible with the standard diffraction data cards. The average particle diameters of composites were calculated using the formula of Debye-Scherrer, and similar results were obtained with the diameters determined by TEM and SEM results. The properties of bond structures of composites were determined by the results of FT-IR analysis. The bandgap energies of Fe3O4, Fe3O4@SiO2, Fe3O4SiO2@ZnO were calculated by the Tauc method using the UV–vis measurement results and found as 1.3, 1.68, and 2.21 eV, respectively. The magnetic properties of composites were determined by VSM analysis. Acid Blue 161 solution was used to evaluate the photocatalytic activities of the produced photocatalyst composites. The experiments carried out in the dark medium revealed that the decomposition of Acid Blue 161 was not due to adsorption. In the experiments performed in the presence of Fe3O4 and Fe3O4@SiO2 composites, the photocatalytic activity was found to be very low. Compared with Fe3O4@SiO2@ZnO composite and commercial ZnO nanoparticles, which show the highest photocatalytic activity, Fe3O4@SiO2@ZnO composite has achieved 100 % the decomposition of Acid Blue 161 within 120 min, while the dye decomposition of ZnO nanoparticles is 70.9 %. The results revealed that the Fe3O4@SiO2@ZnO composite has an effective photocatalytic activity.