Controllable synthesis and optical characterizations of ZnO nanostructures by citric acid-assisted annealing process

By citric acid-assisted annealing process, ZnO nanostructures, including nanorods with diameters ranging from 25 to 88 nm and with length up to 1 μm and polygonal granules with diameters between 200 and 500 nm, were obtained. Morphologies of the ZnO nanostructures were controlled by calcine temperature. The samples were characterized by X-ray diffraction, field-emission scanning electron microscopy (FE-SEM), high-resolution transmission electron microscopy (HRTEM), FTIR spectrophotometer and ultraviolet–visible (UV–vis) spectroscopy. The influence of annealing temperature and time on the synthesis of ZnO nanostructures was investigated. This work presented a simple and effective route for the controllable syntheses of oxide nanostructures.