Synthesis and formation mechanism of ZnO nanotubes via an electrochemical method

ZnO nanotube arrays were synthesized by a two-step process: electrodeposition and selective dissolution. In the first step, ZnO nanorod arrays were grown on an Au/Si substrate by using a homemade electrodeposition system. ZnO nanorod arrays were then selectively dissolved in an etching solution composed of 0.125 M NaOH, resulting in hollow ZnO nanotube arrays. It is suggested that the formation mechanism of the ZnO nanotube arrays might be attributed to the preferred surface adsorption of hydroxide ion (OH ^-1) on a positive polar surface followed by selective dissolution of the metastable Zn-terminated ZnO (0001) polar surface caused by the difference in the surface energy per unit area between the ZnO nanorod and nanotube.