Novel hydrothermal approach to functionalize self-oriented twin ZnO nanotube arrays

• Highly crystalline HCP twin ZnO nanotubes were successfully prepared.
• Phase transformation and morphology evolution in ZnO were demonstrated.
• Deformation twinning in twin ZnO nanotube formation was elucidated.
• Blue shift of optical band gap due to quantum confinement effect was considered.

Surface modification in nanostructures enables a thorough control on intrinsic properties, surface activity and enhancement of their usefulness in several device applications. The crystal growth and design in a low temperature regime (<90 °C) has been intensively studied for the synthesis of highly crystalline nanostructures. In this paper, we demonstrated a novel two-step facile hydrothermal and air cooled hydrolysis method which tuned ZnO nanostructure from single nanorod to twin nanotube. A concise mechanism related to deformation twinning and self-selective phase etching on a-basal plane of ZnO is proposed and evidenced with the existence of (101) peaks under the increment of etching time. The diameter and the interspacing distance of adjacent nanorods were found to be linearly dependent on the etching time. A blue shift in the absorption edge of the synthetic ZnO samples reveals quantum confinement effect.