Synthesis and characterization of transition-metals-doped ZnO nanoparticles by sol-gel auto-combustion method

Transition-metals chromium (Cr) and iron (Fe) doped ZnO nanoparticles are synthesized by sol-gel auto-combustion and characterized by different techniques. X-ray diffraction (XRD) analysis reveals that the synthesized nanoparticles have a typical hexagonal wurtzite structure. The crystallite size measured by Scherrer's formula was in the range of 36-38 nm at different doping concentrations. The scanning electron microscope (SEM) results show the nano-sized nanoparticles with well-defined boundaries are observed. Fourier transform infrared (FTIR) spectra show a wide absorption band at 1589 cm^-1 for whole composition range, corresponding to the stretching vibration of zinc and oxygen Znsbnd O bond. A decrease in optical band gaps from 3.20 eV for ZnO to 3.16 eV for Zn_0.95Cr_0.05Fe_0.05O nanoparticles was observed by UV-Vis spectroscopy analysis. The field-dependent magnetization M-H loops measured by using vibrating sample magnetometer (VSM) reveal that diamagnetic behavior of ZnO nanoparticles changed into ferromagnetic depending on the doping concentration. Our results provided an active route to improve magnetic properties of the ZnO nanoparticles, which may get considerable attention in the coming days.