Size-controlled fabrication of ZnO micro/nanorod arrays and their photocatalytic performance

ZnO micro/nanorod arrays were successfully synthesized on Si substrates using two-step route at low-temperature without any surfactants or templates. The above two steps include spin coating seed on substrates and chemical bath deposition (CBD) growth. The size of ZnO micro/nanorods can be controlled by varying seed density on substrates or NaOH concentration in solution. As a result, the length and diameter of ZnO micro/nanorods changed from 0.6 μm to 7.0 μm and from 70 nm to 4.9 μm, respectively. Meanwhile, the change in aspect ratio, density and orientation of ZnO micro/nanorods was investigated in detail by X-ray power diffraction (XRD), scanning electron microscope (SEM) and transition electron microscopy (TEM). The effects of size, orientation and coverage rate of (0001) facet of ZnO samples on photocatalytic activity were also discussed. The results implied that photocatalytic activity of ZnO micro/nanorods strongly depends on the coverage rate of (0001) facet and the recombination of photogenerated electron–hole pairs.