Hydrothermal growth and optical properties of ZnO nanoflowers

A large amount of ZnO nanoflowers were fabricated on graphene/SiO2/Si substrate by the hydrothermal method. The ZnO nanoflowers were characterized by x-ray diffraction, scanning electron microscopy, energy dispersive x-ray spectrometry, photoluminescence and UV-visible spectrometry. The ZnO nanoflowers were of pure wurtzite phase with good crystalline quality. The shape of the ZnO nanoflowers showed a star-like morphology. Green and orange luminescences in the photoluminescence spectrum were attributed to O vacancies and O interstitials, respectively. Compared with ZnO powder, ZnO nanoflowers exhibited a smaller optical band gap, for which the O vacancy was responsible.