UV irradiation-promoted wet etching of ZnO nanorods to nanotubes

In this work, UV irradiation was introduced to promote the etching process of ZnO nanorods towards nanotubes. The ZnO nanorods with different diameters were grown on Au cylindrical spirals via hydrothermal decomposition, and then in the presence of UV irradiation, they were chemically etched to nanotubes. The results indicate that the ZnO nanorods with the larger diameter are easily etched to nanotubes due to enough oxygen vacancies (a kind of defect) within the centre parts, but the ZnO nanorods with the smaller diameter are difficult to form tubular structures because of the insufficient oxygen vacancies. With the introduction of UV irradiation, more oxygen vacancies are produced in the ZnO nanorods and hence, the nanorods with the larger diameter are etched more quickly, and the nanorods with the smaller diameter are etched more easily. Additionally, the UV light with the shorter wavelength is more beneficial for the formation of the ZnO nanotubes than the one with the longer wavelength. The results benefit the wet etching of ZnO nanorods towards nanotubes, especially those with smaller diameters.