Sol–gel assisted hydrothermal synthesis of ZnO microstructures: Morphology control and photocatalytic activity

•We report a sol−gel assisted hydrothermal method to synthesize ZnO microstructures.•Four kinds of ZnO microstructure were obtained by adjusting the pH of the solution.•The flower-like ZnO shows enhanced photocatalytic activity.•The relationship between microstructure and photocatalytic property is proposed.

ZnO microstructures of different morphologies were synthesized by the sol–gel assisted hydrothermal method using Zn(NO3)2, citric acid and NaOH as raw materials. Twining-hexagonal prism, twining-hexagonal disk, sphere and flower-like ZnO microstructures could be synthesized only through controlling the pH of the hydrothermal reaction mixture at 11, 12, 13 and 14, respectively. The as-synthesized samples were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM). Optical properties were examined by UV–Vis absorption/diffuse reflectance spectroscopy and room-temperature photoluminescence measurements (PL). Photocatalytic activities of the samples were evaluated by degradation of Reactive Blue 14 (KGL). The results indicated that the flower-like ZnO composed of nanosheets possessed superior photocatalytic activity to other ZnO microstructures and commercial ZnO, which could be attributed to the morphology, surface defects, band gap and surface area. The formation mechanisms of different ZnO morphologies were also investigated based on the experimental results.

Graphical abstractSchematic illustration of the formation process of the as-synthesized ZnO samples.Figure optionsDownload full-size imageDownload as PowerPoint slide