Photovoltaic Materials Unit, National Institute for Materials Science, Tsukuba, Ibaraki, Japan.
Sci Rep. 2013;3:1959. doi: 10.1038/srep01959.
Since crystal phase dominantly affects the properties of nanocrystals, phase control is important for the applications. To demonstrate the size dependence in anatase-rutile phase transition of titania, we used quantum-size titania prepared from the restricted number of titanium ions within dendrimer templates for size precision purposes and optical wave guide spectroscopy for the detection. Contrary to some theoretical calculations, the observed irreversibility in the transition indicates the metastablity of anatase; thermodynamics cannot explain the formation of metastable states. Therefore, we take into account the kinetic control polymerization of TiO6 octahedral units to explain how the crystal phase of the crystal-nucleus-size titania is dependent on which coordination sites, cis- or trans-, react in the TiO6 octahedra, suggesting possibilities for the synthetic phase control of nanocrystals. In short, the dendrimer templates give access to crystal nucleation chemistry. The paper will also contribute to the creation of artificial metastable nanostructures with atomic-level precision.
由于晶体相主要影响纳米晶体的性质，因此相控制对于应用非常重要。为了证明二氧化钛中锐钛矿-金红石相转变的尺寸依赖性，我们使用了受限数量的钛离子在树枝状大分子模板内制备的量子尺寸二氧化钛，以达到尺寸精度的目的，并使用光学波导光谱法进行检测。与一些理论计算相反，观察到的转变的不可逆性表明锐钛矿的亚稳性；热力学不能解释亚稳态的形成。因此，我们考虑了 TiO6 八面体单元的动力学控制聚合，以解释在 TiO6 八面体中哪个配位位点，顺式或反式，反应，从而说明了如何控制晶核大小的二氧化钛的晶体相，这为纳米晶体的合成相控制提供了可能性。简而言之，树枝状大分子模板为晶体成核化学提供了途径。该论文也将有助于以原子级精度创建人工亚稳结构的纳米结构。
