Morphological evolution of 3D ZnO hierarchical nanostructures by diethylene glycol-assisted sol–gel synthesis for highly effective photocatalytic performance.

In this study, we focus on synthesizing various 3D ZnO hierarchical nanostructures (ZnH) for highly effective photocatalytic performance via an innovative sol-gel method using diethylene glycol as an assembly-guiding agent. The morphology of 3D ZnH can be turned from nanospheres into nanoplate blocks and nanosheet-based flowers by increasing the concentration of diethylene glycol. Possible growth mechanisms are proposed for different assembly architectures. Analysis of characterization techniques reveal that the synthesized hierarchical structures exhibited a large specific surface area, high degree of crystallinity, and a band gap in the range 2.95–3.11 eV, depending on their morphology. X-ray photoelectron and photoluminescence spectroscopy revealed the presence of rich oxygen vacancies introduced by the 3D ZnO hierarchical morphology. The photodegradation experiment results presented in ZnO nanosheet-based flower shown superior photoactivity of rhodamine B degradation compared with nanospheres and nanoplate blocks structures. This is attributed to the larger surface area, enhanced light absorption, and more effective photogenerated charge separation on account of their rich Vo. The establishment of relevant structural–optical property relationships is expected to provide deeper insights into the potential use of ZnH for innovative devices. Highlights: Three different 3D ZnO hierarchical nanostructures were successfully synthesized. The morphology-optical properties relationship of the obtained samples was studied. Optical properties and oxygen defects are dependent on 3D ZnO hierarchical morphology. The ZnO nanosheet-based flowers exhibit excellent photocatalytic activity. [ABSTRACT FROM AUTHOR]