Li Jing, Zeng Hua Chun
Department of Chemical and Biomolecular Engineering, Faculty of Engineering, National University of Singapore, 10 Kent Ridge Crescent, Singapore 119260.
J Am Chem Soc. 2007 Dec 26;129(51):15839-47. doi: 10.1021/ja073521w. Epub 2007 Nov 30.
The well-known physical phenomenon Ostwald ripening in crystal growth has been widely employed in template-free fabrication of hollow inorganic nanostructures in recent years. Nevertheless, all reported works so far are limited only to stoichiometric phase-pure solids. In this work we describe the first investigation of doped (nonstoichiometric) materials using Ostwald ripening as a means of creating interior space. In particular, we chose the xSnO2-(1 - x)TiO2 binary system to establish preparative principles for this approach in synthesis of structurally and compositionally complex nanomaterials. In this study, uniform Sn-doped TiO2 nanospheres with hollow interiors in 100% morphological yield have been prepared with an aqueous inorganic route under hydrothermal conditions. Furthermore, our structural and surface analyses indicate that Sn4+ ions can be introduced linearly into TiO2, and preferred structural phase(s) can also be attained (e.g., either anatase or rutile, or their mixtures). Fluoride anions of starting reagents are adsorbed on the surface sites of oxygen. The resultant anion overlayer may contribute to stabilization of surface and creation of repulsive interaction among the freestanding nanospheres. On the basis of these findings, we demonstrate that Ostwald ripening can now be employed as a general hollowing approach to architect interior spaces for both simple and complex nanostructures.
晶体生长中著名的物理现象奥斯特瓦尔德熟化近年来已被广泛应用于无模板制备中空无机纳米结构。然而，迄今为止所有报道的工作都仅限于化学计量比的纯相固体。在这项工作中，我们首次描述了利用奥斯特瓦尔德熟化作为创造内部空间的手段对掺杂（非化学计量比）材料进行的研究。具体而言，我们选择了xSnO2-(1 - x)TiO2二元体系来确立这种方法在合成结构和成分复杂的纳米材料中的制备原则。在本研究中，通过水热条件下的无机水溶液路线，以100%的形态产率制备出了具有中空内部的均匀Sn掺杂TiO2纳米球。此外，我们的结构和表面分析表明，Sn4+离子可以线性引入TiO2中，还可以获得优选的结构相（例如，锐钛矿或金红石，或它们的混合物）。起始试剂中的氟阴离子吸附在氧的表面位点上。形成的阴离子覆盖层可能有助于表面稳定以及在独立纳米球之间产生排斥相互作用。基于这些发现，我们证明奥斯特瓦尔德熟化现在可以用作一种通用的中空方法，为简单和复杂的纳米结构构建内部空间。
