Nosheen Shaneela, Galasso Francis S, Suib Steven L
Department of Chemistry, University of Connecticut, 55 North Eagleville Road, Storrs, Connecticut 06269-3060, USA.
Langmuir. 2009 Jul 7;25(13):7623-30. doi: 10.1021/la9002719.
A phase transition was achieved from TiO2 particles to titanate nanotubes by the breakage of Ti-O bonds without using expensive precursors, high temperatures, high chemical concentrations of alkaline solutions, and long synthesis times. The controlled preparation of one-dimensional nanostructures of titanates (H2Ti4O9.nH2O) has been conducted at a very low concentration of alkaline solution (1 M NaOH), and in a very short time (12 h) using TiO2 anatase and TiO2 P-25 (precursors) and a microwave enhanced soft chemical process. Temperature was used as a variable, and only low process temperatures (100-110 degrees C) were used. A combination of anatase nanoparticles/hydrogen tetratitanate nanotubes was synthesized using TiO2 (anatase) and a temperature of only 100 degrees C. When TiO2 (P-25) was used with the same concentration of alkaline solution (1 M NaOH), the same processing time of 12 h, and a higher temperature at 110 degrees C, only hydrogen tetratitanate nanotubes were observed. The linkages of "Ti-O" play a very important role in the structural features of different phases. X-ray diffraction (XRD) showed two crystalline phases (tetragonal and monoclinic) in the case of TiO2 (anatase) and one crystalline phase (monoclinic) for products of TiO2 (P-25). The role of Ti-O linkages is obvious in the Raman spectra as revealed by a shift in peak positions for a layered structure of the hydrogen tetratitanate and a nanosphere structure of the resulting TiO2. An X-ray photoelectron spectroscopy (XPS) study showed a shift to a lower binding energy of the 2p peaks (2p1/2, 3/2) in the Ti region for titanate and confirmed the formation of titanate nanostructures. Transmission electron microscopy (TEM) revealed nanotubes of hydrogen tetratitanates (H2Ti4O9.nH2O) in the form of bundles. High-resolution TEM (HRTEM) data supported findings of X-ray diffraction results of the products of TiO2 (anatase) and TiO2 (P-25).
在不使用昂贵前驱体、高温、高浓度碱性溶液以及长时间合成的情况下，通过Ti - O键的断裂实现了从TiO₂颗粒到钛酸盐纳米管的相变。采用TiO₂锐钛矿和TiO₂ P - 25（前驱体），利用微波增强软化学过程，在非常低浓度的碱性溶液（1 M NaOH）中，在非常短的时间（12小时）内实现了钛酸盐（H₂Ti₄O₉·nH₂O）一维纳米结构的可控制备。以温度作为变量，仅使用了较低的工艺温度（100 - 110℃）。使用TiO₂（锐钛矿）并仅在100℃的温度下合成了锐钛矿纳米颗粒/四钛酸氢钠纳米管的组合。当使用相同浓度的碱性溶液（1 M NaOH）、相同的12小时处理时间以及110℃的较高温度时，仅观察到四钛酸氢钠纳米管。“Ti - O”键在不同相的结构特征中起着非常重要的作用。X射线衍射（XRD）表明，TiO₂（锐钛矿）的情况下有两个晶相（四方相和单斜相），而TiO₂（P - 25）的产物有一个晶相（单斜相）。如四钛酸氢钠的层状结构和所得TiO₂的纳米球结构的拉曼光谱中峰位的移动所示，Ti - O键的作用在拉曼光谱中很明显。X射线光电子能谱（XPS）研究表明，钛酸盐的Ti区域中2p峰（2p1/2、3/2）的结合能向较低值移动，证实了钛酸盐纳米结构的形成。透射电子显微镜（TEM）揭示了呈束状的四钛酸氢钠（H₂Ti₄O₉·nH₂O）纳米管。高分辨率TEM（HRTEM）数据支持了TiO₂（锐钛矿）和TiO₂（P - 25）产物的X射线衍射结果。
