Particle Technology Laboratory, Department of Mechanical and Process Engineering, ETH Zurich, Sonneggstrasse 3, CH-8092 Zurich, Switzerland.
Langmuir. 2010 Apr 20;26(8):5815-22. doi: 10.1021/la9037149.
Hydrophilic TiO(2) particles made in a flame aerosol reactor were converted in situ to hydrophobic ones by silylation of their surface hydroxyl groups. So the freshly formed titania aerosol was mixed with a fine spray of octyltriethoxysilane (OTES) in water/ethanol solution and functionalized continuously at high temperature. The extent of functionalization and structure of that surface layer were assessed by thermogravimetric analysis (TGA) coupled to mass spectroscopy (MS), differential scanning calorimetry (DSC), Fourier transform infrared (FTIR), and Raman spectroscopy. Product particles were characterized also by transmission electron microscopy (TEM), X-ray diffraction, and nitrogen adsorption. The influence of titania specific surface area (SSA) and OTES solution concentration on the functional group surface density was investigated. The titanium dioxide surface was covered with functional groups (up to 2.9 wt %) that were thermally stable up to 300 degrees C in air at an average density of 2 OTES/nm(2). Such surface-functionalized particle suspensions in 2-ethylhexanoic acid and xylene were stable over several weeks. In contrast, as-prepared hydrophilic TiO(2) precipitated within days in these solvents.
在火焰气溶胶反应器中制备的亲水 TiO(2) 颗粒通过表面羟基的硅烷化原位转化为疏水性颗粒。因此，将新形成的 TiO(2) 气溶胶与水/乙醇溶液中的八乙氧基硅烷（OTES）的细雾混合，并在高温下连续进行功能化。通过热重分析（TGA）与质谱（MS）、差示扫描量热法（DSC）、傅里叶变换红外（FTIR）和拉曼光谱联用评估表面层的功能化程度和结构。还通过透射电子显微镜（TEM）、X 射线衍射和氮气吸附对产物颗粒进行了表征。考察了 TiO(2) 比表面积（SSA）和 OTES 溶液浓度对表面功能团密度的影响。TiO(2) 表面覆盖有功能团（高达 2.9wt%），在空气中于 300°C 下热稳定性良好，平均密度为 2 OTES/nm(2)。在 2-乙基己酸和二甲苯中，这种表面功能化的颗粒悬浮液在数周内保持稳定。相比之下，在这些溶剂中，未经处理的亲水 TiO(2) 在数天内就会沉淀。
