Instituto de Física de São Carlos, Universidade de São Paulo, Avenida Trabalhador São-carlense, 400, 13566-590, São Carlos, SP, Brazil.
Phys Chem Chem Phys. 2013 Aug 7;15(29):12386-93. doi: 10.1039/c3cp50643f. Epub 2013 Jun 20.
We report herein a detailed study on the influence of microwave-assisted hydrothermal (MAH) treatment time on both long and short range structures around Ti atoms of SrTiO3 powders. Few studies have been carried out on short-order structural properties as well as the relationship between the local order and the SrTiO3 photocatalytic properties. We use X-ray diffraction to determine the long-range structure, while the local environment around the Ti atom is probed with X-ray absorption spectroscopy and the vibration frequencies are investigated by Raman spectroscopy. The faster crystallization of SrTiO3 powders provided by the MAH system resulted in large distortions of Ti-O bond lengths which remain unchanged even for a longer MAH treatment time. Despite the long-range structure being associated with ideal TiO6 clusters, X-ray absorption spectroscopy measurements identified the presence of undercoordinated TiO5 clusters. Compared with the reference bulk SrTiO3, the hierarchical SrTiO3 cube-like shape showed enhanced photocatalytic activity, which was associated with the presence of these TiO5 clusters. Field emission scanning electron microscopy (FE-SEM) revealed that the superstructures based on a cube-like shape are formed by an assembly process, becoming well defined as a function of MAH treatment time.
我们在此详细研究了微波辅助水热（MAH）处理时间对 SrTiO3 粉末中钛原子的长程和短程结构的影响。很少有研究涉及短程结构特性以及局部有序与 SrTiO3 光催化性能之间的关系。我们使用 X 射线衍射来确定长程结构，而使用 X 射线吸收光谱来探测 Ti 原子周围的局部环境，并通过拉曼光谱研究振动频率。MAH 系统提供的 SrTiO3 粉末更快的结晶导致 Ti-O 键长度的大幅扭曲，即使 MAH 处理时间更长，这些键长也保持不变。尽管长程结构与理想的 TiO6 簇有关，但 X 射线吸收光谱测量表明存在配位不足的 TiO5 簇。与参考体相 SrTiO3 相比，具有层次结构的 SrTiO3 立方体形貌表现出增强的光催化活性，这与这些 TiO5 簇的存在有关。场发射扫描电子显微镜（FE-SEM）显示，基于立方体形貌的超结构是通过组装过程形成的，并且随着 MAH 处理时间的增加变得更加明确。
