Cobalt doping induced shape transformation and its effect on luminescence in zinc oxide rod-like nanostructures

The structural and optical propertie of semiconducting oxide nanomaterials offer several possibilities for applications in photocatalytic activities, solar cells and gas sensing owing to their reduced dimensions and large surface/volume ratios as compared to their bulk counterparts. In this study, undoped and Co doped ZnO nanostructures were prepared by a chemical co-precipitation method. The XRD patterns confirmed that all the samples were crystalline with a wurtzite hexagonal phase without forming any additional phases. A drastic change in the morphology from the transformation of spherically shaped nanoparticles (NP’s) to rod-like shaped NP’s after Co doping was revealed by SEM and TEM micrographs. Raman spectra confirmed the presence of a defect associated peak in Co doped ZnO NP’s. A direct correlation of change in surface morphology after Co doping was observed with PL emission, where near band edge emission in undoped ZnO was transformed into strong blue defect emission