Ultrasound-assisted synthesis of six-fold-symmetrical ZnO hierarchical architecture assembled by nanorods arrays

Wurtzite ZnO with six-fold-symmetry hierarchical architecture was successfully fabricated by a simple sonochemical method at 40 °C. The structure and the morphology of the hierarchical ZnO characterized by X-ray diffraction spectra, scanning electron microscopy, transmission electron microscopy and high-resolution show that hierarchical ZnO is assembled with six nanorods arrays, standing perpendicular to a central axis of prism ZnO nanorods. The nanorod arrays epitaxially grow on the side face of the central ZnO nanorod with a 6-fold symmetry. A formation mechanism of hierarchical ZnO is also proposed in the paper. Ostwald-ripening assisted oriented attachment plays a crucial role in the growth behavior.