| With China's rapid economic development, environmental pollution, energy shortages and the people physical health become increasingly serious problems. In this thesis, with the rapid screening and remove the organic pollutants as goal, to improve the optical/electrical activity of the titanium dioxide nanotube arrays, we carry out the basic research in the field of function of titanium dioxide nano-composite materials in biosensing and removal of organic pollutants.Since their discovery in 2001, TiO2 nanotube (NT) arrays have been found great applications in photocatalytical and sensing fields, due to their highly ordered orientation, uniform surface morphology, adjustable pore size, length and special electrical, optical properties. However, the wide band gap of TiO2 (anatase Eg=3.2eV, rutile Eg=3.0eV) limits its effective utilization of sunlight since it can only absorbs UV light (λ< 400 nm). On the other hand, the low conductivity of TiO2 semiconductor materials can not effectively transfer the photogenerated pairs. The high photogenerated electrons-holes recombination reduces the photoconversion efficiency. This thesis studies the issues above, through doping and modification of the TiO2 NTs to enhance their absorption in visible light and increase the photoconversion efficiency. We have investigated the structure-activity relationship of functional nano-TiO2 composite materials and application the composites materials in the sensing and removal of the organic pollution. Specific contents are as follows:For the energy shortage problems, in this study we first carried out sensitization of TiO2 NTs and improve the photocatalytic efficiency of water into hydrogen. Organic metal complexes have a high absorption coefficient in the visible region and good electron transmission in their conjugated region form. Organic metal complexes M(bpy)2(FcphSO3)2 (M=Cu2+, Cd2+, Zn2+) were self-assembled onto the highly ordered TiO2 NT arrays. The designed composite allows more efficient light harvesting and photoelectrons transmission. Adding the electron donor to consume the photogenerated holes can reduce the electron-hole recombination. We studied the relationship between the electron donor type and catalytic efficiency. In the study of the three electron donor (acetone, methanol and ether), the ether shows the strongest electronic capabilities. In the presence of 3% ether alkaline, the photocurrent of TiO2 NTs was increased with an 8.8 times enhancement.The work function of noble metal (such as Au and Pt) is higher than that of TiO2. Electrons migrate from TiO2 to the vicinity of the metal particles, resulting in the formation of a Schottky barrier at each metal-semiconductor contacting region. The Schottky barrier can serve as an efficient electron trap to avoid the electron-hole recombination in a photocatalytic process, thereby enhance the photocatalytic activity of the electrode materials. At the same time, the excellent conductivity of noble metal is conducive to electronic transmission. Noble metal can be successfully deposited onto/into TiO2 NT arrays. The Au, Pt nanoparticles greatly promoted the photocatalytic activity of the TiO2 NTs. For Au nanoparticle-modified TiO2 NTs, the photoelectrocatalytic degradation rates for methyl orange (MO) and 2, 4, 6-trinitrophenol (TNP) were enhanced by 1.5 and 1.2 times, respectively. Benefiting from the synergistic effect between the TiO2 NTs and noble metal Au-Pt nanoparticles, the constructed glucose biosensor exhibits good electrocatalytic activity, with a linear response to glucose in the range of 0.1 0.8 mM and a detection limite of 0.1 mM.Based on the band matching principle, we have selected appropriate narrow-band semiconductor materials to composite with TiO2. When the conduction band of selected narrow-band semiconductor more negative than that of TiO2, the photogenerated electrons more easily transfer to the conduction band of TiO2, while the photogenerated holes accumulate in the valence band of the narrow-band semiconductor to form hole centers, which can be consumed by participation in oxidation. Therefore, the modification of narrow-band semiconductor materials can not only enhance the absorption of visible light can also promote the photo-carriers separation, thereby enhancing the optical properties of composite materials. Based on this, we studied the photocatalyic properties of narrow-band binary or ternary semiconductor heterostructures (CdS, CdSexTe1-x, ZnxCd1-xSe)/TiO2 composite materials. CdS nanoparticles and nano-Pt modified TiO2 NT arrays shows enhanced bactericidal effect to E. coli. Photoelectrochemical immunosensor based on CdSexTe1-x/TiO2 NTs performs ultra-sensitive, highly selective response to persistent organic pollutants pentachlorophenol (PCP), with a detection limit of 1 pM. This work opened a new perspective for the application of semiconductors in analytical field.In this thesis, we have designed, developed and applied the composite nano-materials based on TiO2 nanotube arrays. These researches have developed the photoelectric analysis sensoring technology based on semiconductor materials; the novel label-free immunosensor has unsealed the application of semiconductor materials in photoelectrochemical analysis. We have explored the bactericidal effect of multiple heterogeneous nanocomposites. This thesis provides a new way to realize the lock and remove of the environmental pollutants. We have investigated the performance of new electrode materials; it is a useful exploration to solve the energy shortage.
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