Wu Yu, Liu Hong-Mei, Xu Bo-Qing, Zhang Zao-Li, Su Dang-Sheng
Innovative Catalysis Program, Key Lab of Organic Optoelectronics & Molecular Engineering, Department of Chemistry, Tsinghua University, Beijing 100084, China.
Inorg Chem. 2007 Jun 11;46(12):5093-9. doi: 10.1021/ic070199h. Epub 2007 May 15.
Single-phase titania nanomaterials were prepared by autoclaving titanium tetrachloride in acetone at 80-140 degrees C. Depending on the molar ratio of TiCl4 to acetone (TiCl4/Ac), TiO2 materials with different phases and morphologies were obtained. When the TiCl4 concentration was no higher than TiCl4/Ac=1/15, single-phase anatase TiO2 nanocrystals in sizes ranging from 4 to 10 nm were prepared by tuning TiCl4/Ac ratios from 1/90 to 1/15. However, when the TiCl4 concentration was high enough (e.g., TiCl4/Ac>or=1/10), single-phase rutile TiO2 nanofibers were obtained selectively. The materials were characterized comprehensively using X-ray diffraction, transmission electron microscopy, Raman spectroscopy, thermogravimetric analysis, and nitrogen adsorption measurements. With the aid of GC/MS analysis of organic products in the liquid phase, it is shown that the controlled hydrolysis of TiCl4 with water, which was in situ generated from the TiCl4-catalyzed aldol condensation reactions of acetones, played an important role in the formation of the titania nanomaterials. Some of the organic condensates may function to stabilize the phase and morphology of the materials. This mechanism was also supported by our success in using other ketones as alternatives to acetone in the synthesis.
通过在80 - 140℃的丙酮中对四氯化钛进行水热反应制备单相二氧化钛纳米材料。根据四氯化钛与丙酮的摩尔比（TiCl₄/Ac），可获得不同相和形态的TiO₂材料。当四氯化钛浓度不高于TiCl₄/Ac = 1/15时，通过将TiCl₄/Ac比例从1/90调整到1/15，制备出尺寸在4至10纳米范围内的单相锐钛矿TiO₂纳米晶体。然而，当四氯化钛浓度足够高时（例如，TiCl₄/Ac≥1/10），则选择性地获得单相金红石TiO₂纳米纤维。使用X射线衍射、透射电子显微镜、拉曼光谱、热重分析和氮吸附测量等方法对材料进行了全面表征。借助气相色谱/质谱对液相中的有机产物进行分析，结果表明，由丙酮的TiCl₄催化羟醛缩合反应原位生成的水对TiCl₄的控制水解在二氧化钛纳米材料的形成中起重要作用。一些有机缩合物可能起到稳定材料相和形态的作用。我们在合成中成功使用其他酮替代丙酮的实验也支持了这一机理。
