Synthesizing tubular and trapezoidal shaped ZnO nanowires by an aqueous solution method.

In this paper we present a novel bottom-up method suitable for developing vertically aligned hollow ZnO nanowires, ZnO nanotubes as well as longitudinally half ZnO nanowires. The procedures used for synthesizing such crystals combine chemical and electrochemical growth processes in aqueous solution at low temperatures (<90 °C), with a growth block process. A thin layer of gold, deposited when the nanowire growth process is at half way, has the crucial role of blocking the growth along the intended directions. The possibility of fabricating highly aligned crystals on a wide range of polymeric substrates, including flexible or transparent ones, is also illustrated. Our proposed methods hold potential for new developments in piezotronics and piezophotonics by allowing fabrication of nanodevices in the inner region of the hollow nanowires and nanotubes.