Fabrication,Photocatalysis And Bioactivity Of TiO₂-Based Nanotube Heterojunction With Micro/Nano Structrue

Environment pollution and human health have emerged as two major obstacles for the sustainable development of human society. Titanium oxide ?TiO₂?,as a typical semiconductor material, has exhibited widely potential application in pollutant degradation,solar cells and biomedicine. Anodizing TiO₂ nanotubes,as a photocatalysis material,fabricated on Ti substrate have been proved to been suitable for degradation of originic and inoriginic pollutant due to their large specific surface area, highly ordered alignment, faster electron transfer and good immobilization. However, limited to the broad band gap ?3.0 ?3.2 eV? and low quantum efficiency, TiO₂ nanotubes arrays, as photocatalyst, do still not fullfill the requirement of Industrial application.Meanwhile,TiO₂,as the actual surfce active material of Ti implant, its excellent biocompatibility have been widely reported. TiO₂ nanotubes is a bioactive coating and could foster the deposition of bone-like hydroxyapatite ?HAP? layer The large surface area of TiO₂ NTs and the hollow tubes structrue render it a good platform to load or immobilize functional drugs, trace elements, or growth factors in the realization of in situ controlled delivery to the implant-tissue interfaces to accelerate tissue reconstruction and healing.Consequently, in this thesis, We try to preliminary explore the potential application of TiO₂ nanotubes arrays in photocatalysis and biomedicine. We modified the morphology and compositions of TiO₂ nanotube arrays to furtherly understand the principles of photocatalysis and biological activities enhancement. Related results provide theory and experiment basis of TiO₂ nanotube arrays in photocatalytic pollutants degradation and biological materials. The main content in this work is as follow:1?SrTiO₃/TiO₂ heterojunction nanotubes with dominant ?001? facets of TiO₂ ?SrT? were fabricated by a self-template anodization following an in situ hydrothermal treatment. Their compositions can be adjusted by changing the hydrothermal reaction time. The heteroepitaxial growth on ?001? plane of SrTiO₃ led to dominant ?001? facets of anatase TiO₂ attributing to their excellent surface lattices match. Compared with the pure TiO₂ nanotubes,SrTiO₃/TiO₂ heterojunction nanotubes improved photoelectrochemical properties due to the synergetic contributions of the directional transfer of photo-generated charges and decreased Fermi level arised from heterostructure.2?Micro/nano structural SrTiO₃/TiO₂ heterojunction nanotubes ?MNST? were fabricated on 3D microporous Ti substrate prepared by acid etching. 3D micro/nano structure could not only increase surface areas providing more reactive activesites, but also absorb more light. The enhanced PC activity of MNST can be ascribed to the synergistic contributions of positive heterojunction effect of the SrTiO₃/TiO₂ nanotubes and 3D microporous structure-introduced improvements. Meanwhile, MNST can promote CaP deposition and increase the amount of protein adsorption, benefited from 3D micro/nano structure and SrTiO₃ component.3?Micro/nano structural CaTiO₃/TiO₂ composite were prepared based on 3D microporous Ti substrate. 3D micro/nano porous structure can offer more active sites and benefit CaP,deposition of protein adsorption and cell contact. Meanwhile, CaTiO₃ could release the Ca2+ ions in SBF, the aggregation of Ca2+ ions in the surface can promote the deposition of PO43- and Ca2+ ions and accelerate the biomineralization of CaP. The more protein and cells adsorbed on the surface containing Ca2+ ions. The activity of cells adsorbed on the surface containing Ca2+ ions were higher than samples without containing Ca2+ ions.4.Mo doped TiO₂ nanotube arrays were fabricated by in situ anodization. The doping amount of Mo in TiO₂ nanotubes can be adjusted by charging the additive amount of Na₂MO₄ in the electrolyte. Mo⁶⁺ ions could dope into TiO₂ lattice and replace Ti4+ ions,forming the doping level below TiO₂ conduction band. After Mo doped, Mo-TNTs showed obvious visible-light absorption. The doping level, as the shallow trap of electron, could effectively suppress the recombination of photo-generated charges. Mo-TNTs exhibited excellent photocatalytic activity and reusability under visible-light.