ZnO Nanotube Arrays and Nanotube-Based Paint-Brush Structures: A Simple Methodology of Fabricating Hierarchical Nanostructures with Self-Assembled Junctions and Branches

ZnO nanotube arrays and self-assembled hierarchical nanostructures are reported here. The ZnO nanostructures were synthesized on Zn foils by a simple solvothermal approach. The hierarchical nanostructures resemble the paint-brush morphology, which consisted of a bunch of self-assembled thin nanowires on a comparatively thick ZnO nanotube wall. Successful creation of surface roughness through controlled etching of the ZnO nanotube walls provided the secondary nucleation centers for the nanowires.