ZnO/TiO2 core-brush nanostructure: processing, microstructure and enhanced photocatalytic activity

Heterostructure ZnO/TiO2 core-brush nanostructures were synthesized on glass substrates by a combination of aqueous solution growth and magnetron sputtering method. The microstructure and morphology were characterized using scanning electron microscopy, X-ray diffraction and transmission electron microscopy. The heterostructure core-brush shows the single crystal ZnO nanorod as the core and polycrystalline TiO2 nanowires as the brush-like outer layer. Surface electronic states and optical transmittance were measured using X-ray photoelectron spectroscopy and a UV-vis spectrometer. The growth mechanism was proposed as a slow particle-by-particle mechanism. The photocatalytic activity of the ZnO/TiO2 core-brush nanostructure was evaluated by the decomposition reaction of Bromo-Pyrogallol Red dye under UV (245 nm) and visible-light (450 nm) irradiation. The results revealed that the core-brush structure exhibited much higher photocatalytic activities than that of a TiO2 film and a TiO2/ZnO composite film. The photocatalytic activity enhancement of the ZnO/TiO2 core-brush could be attributed to the interaction effect, lower band gap energy and its unique core-brush feature which can lower the recombination rate of electron-hole pairs, extend the absorption range and provide a high density of active sites.