Sol–gel synthesis, structural, optical and magnetic properties of Co-doped ZnO nanoparticles

We report the synthesis of Zn1−xCoxO nanoparticles prepared by a sol–gel processing technique for x ranging from 0 to 0.05. The structural, morphological, optical and magnetic properties of the as-prepared nanoparticles were investigated by XRD, XPS, transmission electron microscopy, UV measurements, photoluminescence and superconducting quantum interference device. The structural properties showed that the obtained nanoparticles are single phase wurtzite structure and no secondary phases were detected which indicated that Co ions substituted for Zn ions. The energy gap decreased gradually with increasing doping concentration of Co. The photoluminescence spectra show a shift of the position of the ultraviolet emission to long wavelength and the intensity decreases with increasing Co. The Magnetic measurements at room temperature reveal diamagnetic behavior for sample with lower concentration and the presence of both paramagnetic and ferromagnetic behavior for increasing concentration.