Control of the Surface of ZnO Nanostructures by Selective Wet-Chemical Etching

In this article, we demonstrate successful application of a top-down strategy based on a selective wet-chemical etching technique in fabrication of nanostructures with a special morphology. Pagoda-like and hexagonal pyramidal ZnO nanostructures with the polar (000 (1) over bar) and {10 (1) over bar1} planes as exposed surfaces have been synthesized by refluxing ZnO columns mainly bounded with {10 (1) over bar0} nonpolar faces in the mixed solvent of oleic acid (OA) and 1-octylamine. Adequate evidence demonstrates that OA in the mixed solvent acts as the etchant in the process of morphology evolution, and the appropriate proportion of OA, reaction time, and reaction temperature are crucial for controlling the etching degree of ZnO. Through the selective wet-chemical etching, it has been confirmed that the dumbbell-like ZnO is of twinning morphologies growing along contrary direction on both sides of the (0001) twinning plane. Therefore, our present work provides a simple way to estimate the complicated twinning phenomena.