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Nanocrystalline TiO_2 surfactant film modifier and its super-hydrophilic Design and Synthesis

Author: SongZuo
Tutor: FuHongGang
School: Heilongjiang University
Course: Inorganic Chemistry
Keywords: TiO2 nano-materials surface-modification photocatalysis wettability
CLC: TB383.1
Type: Master's thesis
Year: 2008
Downloads: 283
Quote: 2
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Abstract


In recent years, nanosized TiO2 has developed as a new and very attractive application in photoelectric conversion, heterogeneous photocatalysis, antifogging and self-cleaning materials, due to its unique characteristics such as large surface area, strong absorption of ultraviolet and oxidation capability, stable chemical properties and innocuity. However, nanosized TiO2 disperses hardly in non-polar mediums and is prone to congregate in polar mediums, because of its strong polarity and high surface energy, which influences its performance and restricts its application greatly. Furthermore, the superhydrophilicity of nanosized TiO2 film depends on the ultraviolet illumination to a large degree. Therefore, design and synthesis of non-UV activated superhydrophilic nanosized TiO2 film, from the aspect of surface structure, is greatly significative. Based on the above statement, the investigations of surface-modified nanosized TiO2 with anion and cation surfactant, furthermore, design and synthesis of non-UV activated superhydrophilic TiO2 film are carried on in this paper.The nanosized TiO2 surface modified by sodium dodecylbenzenesulfonate （DBS） and cethyltrimethylammonium bromide （CTAB） were prepared respectively, adopting subsequent modification technique. The proper modification conditions of TiO2 were explored. The modified mechanisms were discussed in detail. And the influences of modification on optical and photoinduced charge transfer of nanosized TiO2 were investigated in principle, by means of FT-IR, XRD, Raman, TEM, Uv-Vis and SPS. Moreover the photocatalytic activities of the samples were evaluated by degradation of dye pollutant under the visible-light. The results show that, TiO2 can be surface modified by DBS and CTAB groups under conditions of appropriate pH value and surfactant amounts, so as to transfers to organic phase from water. The modified mechanisms by DBS and CTAB are different, that the former is close related to electrostatic attraction, the latter is also attributed to Br ion. The photocatalytic activity of TiO2 increases remarkably after modified by DBS and CTAB, which is ascribed to that the surface modification extends the spectrum absorption range to long wavelength and enhances the separate efficiency of photoinduced charge carriers, as well as improves the ability of adsorbing organic materials.Base on the surface modification, the nanosized TiO2 films have been fabricated via dipping processes, with un-modified and surfactant-modified TiO2 nanoparticles. The measurements of SEM, Raman, Uv-Vis and CA were employed to investigate the composing, microstructure and wetting performance of the resulting TiO2 films, together with their relationships. The results show that the as-prepared films resulting from surfactant-modified TiO2 nanoparticles exhibit superhydrophilic characteristic and well superhydrophilic stability, although it is not exposed to ultraviolet light. The micro- and nanometer-scale hierarchical structure, that is the micro-papillae composed of many nanosized particles on the film surface, is responsible for its wettability. The possible formation mechanism of micro- and nanometer-scale hierarchical surface structure is suggested mainly on the basis of DBS groups with amphiphilic property, which could enhance the interactivity between polar nanosized TiO2 particles and non-polar oganic macromolecule. So as to the surfactant-modified TiO2 nanoparticles would easily conglomerate due to the shrinkage of the PEG molecule chains during the fabricating processes, which would possibly lead to the formation of the micro- and nanometer-scale hierarchical surface structure.

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