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.