Synthesis and optical properties of Co2+-doped ZnO Network prepared by new precursors

Pure ZnO nanoparticles (NPs) and Co/ZnO alloy NPs were synthesized with different percentages of cobalt impurity (1%, 3%, 5%, and 25%) with new precursors through the coprecipitation method. The structural results of the XRD analysis indicated that the pure and impure samples have a wurtzite hexagonal structure such that with an elevation of Co impurity up to 1%, the size of the nanocrystals declines by up to 30 nm. Furthermore, the FESEM analysis results suggest the homogeneity of the NPs such that with increased cobalt impurity, its level declines. The TEM analysis results revealed that the NPs with 5% impurity have a mean size of 32 nm in spherical form. The FTIR optical analysis results suggest a very sharp absorption peak within the wavelength ranges of 434-448 cm(-1) , belonging to the Zn-O vibration bond. In addition, the absorption peak developed at the wavelength of 3428 cm(-1) is related to the activation of the OH radicals, whose absorption value grows with the addition of an impurity, thereby, causing enhanced photocatalytic activity. The UV-DRS optical analysis indicated that the absorption wavelength grows with increased impurity, causing the development of redshift and a reduction of the energy band gap. In this regard, for the pure sample, the band gap value was 3.18 eV, while for the sample with 5% impurity, the band gap was obtained as 2.68 eV. The VSM magnetic analysis suggests ferromagnetic development in the impure sample, with a saturation magnetism of 16 memu g(-1) and a coercivity field of 342 G.