Ionic-strength induced control of the shape and the aspect ratio of ZnO nano-structures prepared by using the hydrothermal process

Abstract

Control of the morphology and the aspect ratio of zinc oxide nanostructures by varying mainly the anionic and cationic strengths of the mother solution in the hydrothermal process is reported. This is studied by choosing five different cationic ([Zn²⁺]) concentrations in two different anionic ([OH⁻]) concentrations each, giving totally ten combinations. A change in the concentration of the mother solution greatly altered the size and the aspect ratio of the nanostructures, as seen in the scanning electron microscopy images of the nanostructures. Changing the ionic strength directly influenced the growth parameters such as the interfacial energy and the formation of nuclei, which resulted in different nanostructures. By using an X-ray diffraction analysis, we confirmed the produced nanostructures to be wurtzite-structured hexagonal zinc oxide in all cases. A characteristic predominant growth along the polar planes with angular tips was also observed by using transmission electron microscopy.