The Effect of Cobalt dopants on the Structural and Optical Properties of ZnO Oxide Nanocrystals prepared by coprecipitation method.

In this study, pure ZnO and Co-doped ZnO nanoparticles were synthesized with cobalt dopants of 5% and 10% with new zinc sulfate and cobalt chloride precursors in the presence of NaBH4 and CTAB stabilizers. In order to determine the crystalline, optical and morphological properties of the samples, XRD, TEM FTIR, EDX, FESEM and UV-DRS were analyzed. The XRD results showed that the samples had a hexagonal structure. Also, x-ray diffraction results showed that the size of the nanoparticles is reduced to 40 nm by increasing Co dopant up to 10%. The results of the FESEM analysis show the uniformity of nanoparticles is reduced with the increase in the cobalt impurity. Elemental analysis (EDX) revealed that weight percent of zinc element for samples with impurity of 0%, 5% and 10%, was 81% wt, 79.2% wt and 74.4% wt, respectively, which indicates that the cobalt impurities penetrates into the Zn matrix. The results of the TEM analysis showed that nanoparticles are quasi spherical with average diameter of 55 nm for 5% impurity. The results of the FTIR analysis indicate a very high absorption peak in the 434 cm-1 frequency belonging to the Zn-O vibrating band and the absorption peak generated in the 3434 cm-1 wavenumber associated with the activation of OH radicals which increase the photocatalytic activity in this sample. The UV-DRS analysis showed that the band gap energy of the sample decreases from 3.7 eV to 2.88 eV for pure and doped samples, respectiviely.