Nafion薄膜中单分散TiO2纳米晶体的合成

采用全氟化离子聚合物薄膜(钠型Nafion薄膜)作模板合成了平均直径为4.0nm的TiO₂晶体粒子。利用高分辨电子显微镜(HRTEM)、X-射线衍射仪(XRD)和紫外-可见光谱仪(UV-VIS)，对Nafion中TiO₂的含量、粒子大小分布、相变条件、纳米晶体微观型貌及其结构、Nafion薄膜结构和TiO₂粒子形成机理等进行了研究。研究结果表明，Nafion中Ti⁴⁺含量不仅与起始原料有关，还与起始物浓度有关。TiO₂在Nafion中的形成速度主要受控于水在膜中的扩散速度，而TiO₂晶体粒子的大小与分布则取决于Nafion的孔径，与起始原料种类以及晶化条件无关。文中还探索了无定型TiO₂转变成单分散晶体的各种途径，详细讨论了TiO₂晶体粒子合成的影响因素。

Preparation of Nanocrystalline TiO2 Monodispersed in Nafion Membrane

The nanocrystalline titanium dioxide with an average particle diameter of 4.0nm was synthesized in Nafion membranes. The crystals of titanium dioxide are dispersed singly in Nafion membrane. High resolution transmission electron microscopy(HR TEM), X ray diffraction(XRD) and Uv vis nir spectrophotometer were attempted to characterize the morphologies, grain size distribution, microstructure of Nafion membranes and formation mechanism of the particles. The results show that the quantity of Ti4+ in Nafion depends on the concentration of Ti(OC3H7)4 in soaking solution beside the kind of precursor. The formation rate to transform titanium isopropoxide to TiO2 is controlled by the diffuse of water to enter Nafion via the channels. The size of nanocrystalline matches with the diameter of cavities in Nafion, and is independent of the kind of precursor, the concentration of Ti4+ and Crystallization condition. The effects of changing the variables of the preparation condition on the formation of nanocrystalline titanium dioxide are discussed in detail.