| Energy and the environment are two major problems which the human must face in the21st century. Semiconductor photocatalytic materials has huge application prospect in solving environmental pollution and energy shortage. Light catalysis by using solar energy has been research hot spot. Photocatalytic technology has extensive application prospect in the field of environmental pollution control because of its cheapness, environmental friendliness and high stability, etc. Semiconductor photocatalysis is one of the most active area of research at home and abroad in recent years. Especially with the rapid development of nanotechnology, photocatalytic nanomaterials can decompose environmental pollutants directly by absorbing sunlight, and no secondary pollution. So further study of nano semiconductor photocatalyst is of great significance to solve fundamentally the problem of environmental pollution.TiO2has its excellent photocatalytic activity and photoelectric properties as a member of the nanometer materials. Since1972, Fujishima found hydrogen production from water by photodecomposition in the TiO2electrode, a lot of research on the TiO2photocatalytic properties has been conducted, and it shows a broad application prospect in the photoelectric conversion, pollutants degradation, self clean, sensors and potential high-tech fields such as cancer treatment.TiO2nanotube arrays was prepared by anodic oxidation for the first time since2001, it gives rise to a lot of research interest because of its uniform surface morphology、large specific surface area、adjustable aperture length、high orientation、and the unique electrical and optical properties. Existing research shows that TiO2nanotube arrays has wide application prospection in the field of photocatalysis and sensing. However, due to the large forbidden band width of titanium dioxide(anatase and rutile type titanium dioxide forbidden band width are3.2eV and3.0eV, respectively.), it can only absorb ultraviolet light which accounts for only about5%of the sunlight. In contrast, the visible light accounts for about46%of sunlight energy, hence, the utilization of solar energy is very low. So make TiO2respond to visible light, and thus improve the utilization efficiency of sunlight of TiO2semiconductor materials is a hot spot in the present study. Furthermore, the conductivity of TiO2semiconductor material is low, and can’t transfer photo-generated carriers effectively which make it easier for the photo-generated electron and hole to recombine, and consequently reduce the photoelectric conversion efficiency.This thesis has carried out research aiming at the above problems, with the removal of organic pollutant andrapid screening for the target, and improving optical/electrical catalytic activity of the titanium dioxide nanotubes array as the research focus.The material of TiO2nanotube arrays were modified and improvedin order to improve the utilization ratio and the photoelectric conversion efficiency of sunlight, and application research in the field of organic pollutant removal and biological sensing. The concrete research content is as follows:(1) The preparation, characterization and the study about photocatalysis of the CdTe/TiO2nanotubes:By using pulse electrodeposit technology, the narrow band gap semiconductor CdTe nanoparticles have been modified into TiO2nanotube arrays. Because the band gap (Eg) of CdTe is about1.5eV which matchs well with sunlight energy, it can absorb effectively visible light. The photocatalytically oxidative decomposition of P-Nitrophenol (PNP) with the CdTe nanoparticles-modified TiO2nanotube arrays (CdTe/TiO2NTAs) as catalyst was investigated under visible light (400nm<λ<800nm)irradiation. The CdTe/TiO2NTAs show much higher degradation rate (0.0312min-1) than the unmodified TiO2NTAs (0.0071min-1). The enhanced photocatalytic activity is attributed to the extended absorption in the visible light resulting from the narrow-band-gap semiconductor CdTe and the effective separation of photogenerated carriers.The two main impact factors on PNP photocatalytic degradation efficiency are the initial concentration of the target and the pH value of the solution. The optimum conditions were as follows respectively:10mg/L and pH～3. Under xenon lamp irradiation within2hours,35ml of10mg/L PNP removal rate is almost100%(Chapter2).(2) CdTe/Au-TiO2NTAs was used for photoelectric immune sensing detection of persistent organic pollutants(pops):In this paper, Tris(2,3-dibromopropyl) isocyanurate (TBC) is for the first time as far as we know determined by ultrasensitive photoelectrochemical(PEC) immunoassay using an antibody-modified ternary hybrid CdTe/Au-TiO2nanotube arrays (NTAs) photoelectrode developed by pulse electrodeposition technique. The as-prepared hybrid shows enhanced photon absorption and photocurrent response, which subsequently increased photoelectrical conversion efficiency in the visible region. TBC-antibody (Ab) was developed in rabbits as a result of immunization with BSA-TBC conjugate and covalently cross- linked onto the CdTe/Au-TiO2NT As. Since the photocurrent is highly dependent on the TiO2surface properties, the specific interaction between TBC and the antibody results in a sensitive change in the photocurrent, which displayed a linear range of5.0×10-11-5.0×10-5M and a low detection limit of5.0×10-11M for TBC determination. This proposed strategy highlights the application of TiO2nanotube in visible-light-activated photoelectrochemical biosensing, which could largely reduce the destructive effect of UV light on biomolecules(Chapter3).(3) A perfluorooctane sulfonate (PFOS, C8F17SO3-) molecularly imprinted (MIP) fluorescence sensor was developed by anchoring the MIP polymer on the surface of SiO2NPs via a surface molecular imprinting process. Fluorescence dye and organic amine were covalently immobilized onto the surface of MIP-SiO2NPs to form a hybrid monolayer of dye fluorophores and amine ligands which acted as the receptor sites to bind PFOS(C8F17SO3-) species through the acid-base pairing and hydrogen-bond interaction under acid condition (pH～3.5). The specific binding of PFOS into the recognition cavities in the polymer matrixes results in the fluorescence quenching due to the electron transfer from the fluorescence dye to PFOS. This proposed method can selectively and sensitively detect down to5.57ug L-1of PFOS in water, and a linear relationship has been obtained covering the concentration range of5.57～48.54ug L-1(10.36nM～90.2nM)(Chapter4). |
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