Department of Physical Chemistry and Materials Science, University of Szeged, Aradi vértanúk tere 1., Szeged, Hungary H-6720.
Langmuir. 2013 Mar 5;29(9):3061-72. doi: 10.1021/la304470v. Epub 2013 Feb 19.
High-aspect-ratio titanate nanotubes (NT) and nanowires (NW) were produced by the hydrothermal conversion of TiO2 at 400 K. The titanate morphology was studied by high-resolution transmission electron microscopy (HRTEM). The formation of ordered titanate nanoobjects depended on the time of conversion. Shorter synthesis times favored hollow nanotube production while during prolonged treatment the thermodynamically more stable nanowires were formed. Titanate nanotubes and nanowires were decorated by Rh nanoparticles. The structure and stability of titanate nanocomposites were studied by thermal gravimetric (TG), X-ray diffraction (XRD), X-ray photoelectron spectroscopic (XPS), Fourier transformed infrared spectroscopic (FTIR), and Raman spectroscopic methods. The nanowires preserve their structure up to 850 K, while the nanotubes start to recrystallize above 600 K. FTIR measurements showed that the water and hydroxyl content gradually decreased with increasing temperature in both cases. XPS data revealed the existence of high binding energy, highly dispersed Rh species on both supports. A small portion of Rh may participate in an ion exchange process. Support transformation phenomena were observed in Rh containing titanate nanowires and nanotubes. Rh decorated nanowires transform into the β-TiO2 structure, whereas their pristine counterparts' recrystallize into anatase. The formation of anatase was dominant during the thermal annealing process in both acid treated and Rh decorated nanotubes. Transformation to anatase was enhanced in the presence of Rh. The average diameters Rh nanoparticles were 4.9 ± 1.4 and 2.8 ± 0.7 nm in the case of nanowires and nanotubes, respectively.
高长径比的钛酸盐纳米管（NT）和纳米线（NW）是通过在 400K 下的水热转化 TiO2 制备的。通过高分辨率透射电子显微镜（HRTEM）研究了钛酸盐的形态。有序钛酸盐纳米结构的形成取决于转化时间。较短的合成时间有利于空心纳米管的生成，而在较长时间的处理过程中，热力学上更稳定的纳米线形成。钛酸盐纳米管和纳米线被 Rh 纳米颗粒修饰。通过热重（TG）、X 射线衍射（XRD）、X 射线光电子能谱（XPS）、傅里叶变换红外光谱（FTIR）和拉曼光谱等方法研究了钛酸盐纳米复合材料的结构和稳定性。纳米线在 850K 下保持其结构，而纳米管在 600K 以上开始重结晶。FTIR 测量表明，在这两种情况下，水和羟基含量随温度升高逐渐降低。XPS 数据表明，在两种载体上都存在高结合能、高度分散的 Rh 物种。一部分 Rh 可能参与离子交换过程。在含 Rh 的钛酸盐纳米线和纳米管中观察到载体转化现象。Rh 修饰的纳米线转变成β-TiO2 结构，而其原始对应物则重结晶成锐钛矿。在酸处理和 Rh 修饰的纳米管中，锐钛矿的形成在热退火过程中占主导地位。在 Rh 的存在下，锐钛矿的形成得到增强。纳米线和纳米管中 Rh 纳米颗粒的平均直径分别为 4.9±1.4nm 和 2.8±0.7nm。
