Effect of pH on the morphology of ZnO nanostructures and its influence on structural and optical properties

Pristine ZnO nanostructure of rods, flakes and flowers are synthesized by hydrothermal method, using equimolar aqueous solutions of zinc-nitrate and hexamethylenetetramine at different pH. The influence of pH value on the formation of different morphological structures of ZnO is investigated. The structural and morphological properties were investigated by X-ray diffraction (XRD) studies and field emission scanning electron microscopic (FESEM) analyses. The XRD results confirm that the crystallinity of ZnO nanostructures are improved after annealing with the wurtzite crystal structure. FTIR studies are carried out in order to ascertain the presence of various functional groups present in the material. Optical studies, using Raman and photoluminescence spectroscopy shows presence of novel defects with newly assigned zone boundary phonon mode.