The Photocatalytic And Amphilicity Properties Of Nanosized TiO₂ And Composite Films

In recent years,it has attracted a great deal of attention that how to improve the photocatalytic activity of TiO₂ and prepare the films which possess high photocatalytic activity and photo-induced amphilicity.TiO₂ films,TiO₂-ZnO composite films,CNTs doped TiO₂-ZnO composite films and TiO₂/ZnO,ZnO/TiO₂, TiO₂/(TiO₂-ZnO),ZnO/(TiO₂-ZnO) stromatolith films were synthesized by the sol-gel process with spin-coating machine.Samples were characterized by modern testing means,such as X-ray powder diffraction(XRD),atomic force microscopy(AFM), scanning electron microscope(SEM),and determined the crystal phase,the crystal size,element content,film microstructure and roughness.UV-vis absorption spectra of the TiO₂-ZnO films and CNTs doped TiO₂-ZnO films in the wavelength region 200～800 nm were obtained.The photocatalytic activity and perdurability of samples were investigated by photocatalytic degradation of aqueous methyl orange under ultraviolet(UV) radiation. The photo-induced amphilicity of samples were investigated using H₂O as polarity solution and C₆H₆ as non-polarity solution.The effects of the annealing temperature, annealing time,thickness of films and roughness on the photocatalytic activity and amphilicity were studied.The results show that,doping ZnO can decrease the size of particles,counteract transformation from anatase to rutile,and then lead to a remarkable change in the photocatalytic activity and amphilicity.The best proportion of Zn²⁺ is 10%.The annealing temperature,annealing time,thickness affect crystal phase,the crystal size,element content and roughness of films,consequently affect the photocatalytic activity.TiO₂ film and TiO₂-ZnO composite film with 3 layers annealed at 450℃and 550℃respectively for 2 h has the highest photocatalytic activity,and the degradation rate is 55%and 72%.TiO₂ film and TiO₂-ZnO composite film annealed at 550℃for 2 h with 3 layers has the best amphilicity.The contact angle is 5°(4°) between TiO₂-ZnO film and H₂O(C₆H₆) and its is better than that of pure TiO₂ film which is 6°(5°).Doping CNTs appropriately can decrease the grain size of ZnO/TiO₂,make the recombination of e^-/h⁺ pairs less likely to occur.UV-vis absorption spectrum of CNTs-ZnO/TiO₂ film shows obvious blue shifts compared with TiO₂ and ZnO/TiO₂ film,and has a stability of absorption in visible light areas.When doped amount of CNTs is 1%,the film of CNTs-ZnO/TiO₂ with 3 layers deposited has the best photocatalytic activity.The degradation ratio is 90%.TiO₂/ZnO stromatolith film has the best photocatalytic activity.TiO₂/(TiO₂-ZnO) stromatolith film has the second highest photocatalytic activity and ZnO/TiO₂ film has the lowest photocatalytic activity.TiO₂/ZnO stromatolith film and TiO₂/(TiO₂-ZnO) stromatolith film both have the best amphilicity,which are better than ZnO/TiO₂ and ZnO/(TiO₂-ZnO) stromatolith film.The photocatalytic activity and amphilicity properties of stromatolith films are better than that of pure TiO₂ film.