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|Title:||Study of photocatalytic activities of nanoscaled metal oxides on textiles||Authors:||Qi, Kaihong||Keywords:||Hong Kong Polytechnic University -- Dissertations
|Issue Date:||2009||Publisher:||The Hong Kong Polytechnic University||Abstract:||A systematic study of the synthesis and application of nanoscaled metal oxides with photocatalytic activity was conducted. The synthesis was based on sol-gel nanotechnology at low temperatures and atmospheric pressure. The metal oxide sols were then applied to textile materials to form photocatalytic self-cleaning thin films by a dip-pad-dry-cure process. The main research work was focused on the synthesis, characterization, and application of pure anatase titanium dioxide (TiO₂) and anatase titanium dioxide doped with other materials. The results showed that the anatase titania and its doped forms possess high photocatalytic activity, which was demonstrated by the complete decomposition of bacteria, colorants, red wine and coffee stains. Nanocrystalline anatase TiO₂ sols were prepared under ambient pressure and at temperatures close to or approaching to room temperature using hydrolysis of titanium tetraisopropoxide in an acidic aqueous solution. A comprehensive study was carried out on the surface morphology, crystal phase and particle size of nanocrystalline TiO₂ using field-emission scanning electron microscopy (FESEM), X-ray diffraction spectroscopy (XRD), and high resolution transmission electron microscopy (HRTEM). The effect of catalysts and different temperatures on the formation of anatase TiO₂ and the self-cleaning performance of TiO₂ treated cotton fabrics under UV irradiation were evaluated. These TiO₂ treated cotton fabrics possess significant photocatalytic self-cleaning properties, such as bactericidal activity, colorant decomposition and degradation of red wine and coffee stains. The UV absorption, the mechanical properties and durability of TiO₂ treated cotton fabrics were investigated. Anatase TiO₂ prepared by an aqueous sol-gel process at 60 °C was applied to polyester fabric since polyester is the most widely applied synthetic fibre in textile and clothing. Due to the poor adhesion between the TiO₂ and polyester fibres, low temperature plasma (LTP) pretreatment of polyester fibres using oxygen gas was performed. The wettability of polyester towards the titania sol and the adhesion of titania layers to polyester fibres were improved as a result of the introduction of negative groups COO-,-O-O- onto polyester surface. The self-cleaning properties, such as bactericidal activities, colorant decomposition and degradation of red wine and coffee stains, of the anatase functionalized polyester fibers were studied. The surface morphological changes of polyester fibers before and after plasma treatment, and of plasma-treated fibers before and after applying anatase titania film were characterized by SEM. The adhesion between the anatase titania and polyester fibers was investigated.
To improve the photocatalytic activity of TiO₂ films, the anatase TiO₂/SiO₂ nanocomposites were investigated. Anatase TiO₂/SiO₂ nanocomposites were developed in an aqueous solution by a sol-gel process at a low temperature. The morphology of these nanocomposites was characterized by SEM, showing that TiO₂ nanoparticles were deposited on the surface of SiO₂ spheres. The spherical TiO₂/SiO₂ nanocomposites treated cotton fabrics demonstrated higher photocatalytic activity in comparison to pure TiO₂ treated cotton fabrics in a typical photocatalytic test using a model compound of Neolan Blue 2G dye. The enhanced photocatalytic activities of the TiO₂/SiO₂ treated cotton fabrics was considered attributable to the increased specific surface area and the enhanced surface acidity of nanocomposites. To eliminate the need for high temperature operations and the use of corrosive chemicals such as nitric acid and hydrochloric acid in synthesizing anatase TiO₂, a new synthesis method for single-phase anatase TiO₂ was developed using a sol-gel process in aqueous media followed by aging at room temperature. The self-cleaning activities of the as-prepared TiO₂ thin films deposited on cotton fabrics were evaluated by the photodegradation of Neolan Blue 2G and the decomposition of red wine and coffee stains. The UV absorption, tensile strength and durability to laundering of the TiO₂ treated cotton were also studied. This study further optimizes the synthesis conditions for anatase TiO₂ which could contribute to the large scale fabrication of self-cleaning textiles. To extend the absorption of TiO₂ into visible region of the spectrum and to reduce electron-hole recombination to further improve photocatalytic activity of TiO₂ in UV-Visible region, Fe³⁺ doped TiO₂ photocatalytic self-cleaning system was investigated. The synthesis was based on a sol-gel process in an aqueous solution at a temperature of 60 °C with the addition of Fe³⁺ dopant. The doping reduces the band gap energy and increases the wavelength response range extending to visible region. The Fe³⁺ dopant with various doping level was also studied. It was found that higher photocatalytic activity was achieved at optimum doping level compared to that of the pure TiO₂ system under both UV irradiation and a visible light source without UV. The study revealed that anatase TiO₂-based self-cleaning system is one of the most promising systems for the development of self-cleaning textiles that would have high potential in commercialization with the advantages of being environmentally friendly, low cost, energy and water saving due to the reduced laundry requirements of the treated items.
|Description:||xxxii, 192 leaves : ill. (some col.) ; 30 cm.
PolyU Library Call No.: [THS] LG51 .H577P ITC 2009 Qi
|URI:||http://hdl.handle.net/10397/2627||Rights:||All rights reserved.|
|Appears in Collections:||Thesis|
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