Effect of synthesis conditions on the growth of various ZnO nanostructures and corresponding morphology-dependent photocatalytic activities

Well-aligned ZnO nanorod arrays have been prepared by using seed-assisted hydrothermal method, in which the c-axis oriented ZnO films prepared by a soft-chemical were used as the seed layers on quartz glass. The epitaxial growth mechanisms and corresponding morphology effect of samples are discussed. The results show that the morphology of ZnO nanorod arrays is closely related to the hydrothermal temperature, pH value and initial concentration of Zn source in precursor solution. The as-prepared samples are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Brunauer-Emmett-Teller (BET), Raman spectroscopy, photoluminescence (PL) spectra and UV-vis spectra. The well-aligned ZnO nanorod arrays exhibit improved photocatalytic degradation with Rhodamine 6G (R6G) solution under UV radiation, according with the UV-vis spectra investigation and photocatalytic improvement speculation. Noteworthy, the photocatalytic properties of well-aligned ZnO nanorod arrays have obviously improved comparing with other ZnO samples without proper alignment. The oxygen vacancies suppressed recombination process of photon induced electrons and holes, as the oxygen vacancy trapped the charge carriers.