Investigation on the influence of dichromate ion on the ZnO nano-dumbbells and ZnCr₂O₄ nano-walls

The effect of in situ addition of K₂Cr₂O₇ in controlling morphology, composition, structural and optical properties of ZnO nanostructures prepared by hydrothermal technique have been investigated. The effect of increasing dichromate ion concentration on the size and shapes of the ZnO nanostructures and spinel ZnCr₂O₄ nanowalls has been studied using field emission scanning electron microscopy and X-ray diffractometer. Further the optical properties of these nanostructures were investigated using photoluminescence spectroscopy, which showed emission in UV and visible regions. From diffused reflectance spectroscopic analysis the direct band gap of ZnO nanodumbbells and ZnCr₂O₄ nanowalls was estimated to be 3.27 and 3.7 eV respectively. The observed results have been explained on the basis of anisotropic growth of ZnO nanostructures in the presence of dichromate ion. Thus, we report a method to control the shape and dimension of nanostructures by varying concentration of dichromate ion, the reported nanostructures have tremendous potential for future development of ZnO based optoelectronic devices.