TiO₂纳米晶的表面活性剂修饰及其超亲水性薄膜的设计合成

【作者】 宋姝；

【导师】 付宏刚；

【作者基本信息】 黑龙江大学 ， 无机化学， 2008， 硕士

【摘要】 近年来,TiO₂纳米材料由于具有比表面积大、紫外光吸收性能好、氧化还原性强、化学性质稳定、无毒等独特的性能,在光电转换、多相光催化以及防雾自清洁材料等许多领域引起广泛关注。但是,纳米TiO₂本身的强极性和高表面能使其不易分散在非极性介质中,且在极性介质中又易团聚,以至于在很大程度上影响其性能发挥以及应用。目前纳米TiO₂薄膜主要依赖紫外光照来实现超亲水性,而从薄膜表面结构入手设计合成非紫外光照超亲水性纳米TiO₂膜是非常有意义的。基于以上陈述,本论文开展了TiO₂纳米晶的阴、阳离子表面活性剂修饰及进一步设计合成超亲水性薄膜的研究。本论文利用阴离子表面活性剂十二烷基苯磺酸钠（DBS）和阳离子表面活性剂十六烷基三甲基溴化铵（CTAB）分别对溶胶-水热法合成的TiO₂纳米晶进行修饰,重点考察了表面修饰的适宜条件,并通过FT-IR、XRD、Raman、TEM、Uv-Vis、SPS等测试技术对样品进行表征,揭示表面修饰机制及对TiO₂光学和光生电荷转移行为等的影响规律。此外,利用可见光下降解染料污染物来评价样品的光催化性能。结果表明:在适宜的pH范围和表面活性剂用量条件下,DBS和CTAB基团均能够较好地修饰在TiO₂纳米粒子表面,以至于实现其由水相到有机相的转移。两种表面活性剂的修饰机制是不同的,DBS主要通过静电吸引作用实现在酸性条件下的修饰。而CTAB可通过静电作用和Br离子分别实现在碱性和酸性条件下的修饰。DBS和CTAB表面修饰后,TiO₂纳米晶的光催化性能得到明显改善,这主要与表面修饰提高了TiO₂光生载流子分离效率、吸附有机物能力及可见光利用率等有关。在表面活性剂修饰TiO₂纳米晶基础上,进一步利用其通过浸渍-提拉过程制备了薄膜,主要通过SEM、Raman、Uv-Vis、CA等测试技术对薄膜的组成、表面微结构及润湿性能进行表征,重点探讨了薄膜表面微结构、组成与性能的关系。结果表明:在紫外光未辐照的条件下,利用表面活性剂修饰的TiO₂所获得的薄膜样品即表现出了超亲水性,这主要与在薄膜表面形成了由TiO₂纳米粒子团聚成的微米级隆起结构有关。而纳-微米复合隆起结构的形成主要归因于表面活性剂分子具有双亲性,增强了极性的TiO₂纳米粒子与非极性的有机高分子之间的相互作用,以至于在成膜过程中TiO₂纳米粒子能够随高分子链的收缩而聚集,最终形成微米级隆起结构。更多还原

【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.更多还原