Synthesis and Characterization of Flower-Like Bundles of ZnO Nano sheets by a Surfactant-Free Hydrothermal Process

Flower-like bundles of ZnO nano sheets have been prepared by using preheating hydrothermal process without any surfactants. The flower-like bundles consist of many thin and uniform hexagonal-structured ZnO nano sheets, with a thickness of 50 nm. The selected area electronic diffraction (SAED) and high-resolution transmission electron microscope (HRTEM) images indicate that the ZnO nano sheets are single crystal in nature. The growth mechanism of the flower-like bundles of ZnO nano sheets is discussed based on the morphology evolution with growth times and reaction conditions. It is believed that the formation of flower-like bundles of ZnO nano sheets is related to the shielding effect of OH^- ions and the self-assembly process, which is dominated by a preheating time. Room temperature photoluminescence spectra results show that the annealing atmosphere strongly affects the visible emission band, which is sensitive to intrinsic and surface defects, especially oxygen interstitials, in flower-like bundles of ZnO nano sheets