Controllable synthesis of hierarchical ZnO nanostructures via a chemical route

The strategy to manipulate nanoscale building blocks into well-organized hierarchical architectures is very important to both material synthesis and nanodevice applications. In this work, hierarchical ZnO nanostructures with controllable morphology were synthesized by a two-step chemical route. At step-one, hexagonal- and spherical-shaped ZnO nanostructures were deposited on glass slide substrates. At step two, the morphology of hierarchical ZnO nanostructures could be effectively controlled by changing the composition of solutions. The method described here is a simple and reproducible process, which does not require any templates, catalysts, or surfactants, but can control the morphology of ZnO crystals from simple to complex. The morphologies and structures of the products were characterized by field-emission scanning electron microscopy and X-ray diffraction measurements. Room-temperature photoluminescence spectra demonstrate that the variety of nanostructures can cause the variation of the photoluminescence intensity, suggesting that the controlled morphologies can be used to modulate the optical properties of ZnO nanostructures.