Simple hydrothermal preparation of new type of sea urchin-like hierarchical ZnO micro/nanostructures and their formation mechanism

We have used a simple hydrothermal method with single ammonia-based system to successfully fabricate 3D sea urchin-like hierarchical ZnO micro/nanostructures. Synthesized products were characterized by X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy, electron energy-dispersive spectroscopy, and UV–vis diffuse reflectance spectroscopy. The results showed the effect of the reaction time on the morphologies of ZnO micro/nanostructures and UV–vis absorption spectra. The sea urchin-like ZnO samples were shown to be typical wurtzite structures with high crystallinity and better absorption in the UV-light region with several 1D ZnO nanoneedles radiating from their centers. On the basis of experimental results, the formation mechanism of sea urchin-like hierarchical ZnO micro/nanostructures was elucidated from the viewpoint of nucleation and self-assembly of building blocks, which would be the foundation of their applications.