From birth to growth of metastable metal oxides in ionic liquids

众所周知，化学中瞬态态的能量会受到周围溶剂的决定性影响，化学反应的结果也是如此。同样在材料科学中，人们可以将纳米种子解释为产生形状颗粒或具有替代晶体结构的相的瞬变状态。在这两种情况下，人们通常对热力学上不太受欢迎的(亚稳定)产品感兴趣，分别是不寻常的形状或多晶型。除了晶体结构外，晶体的形状也是决定其性能的重要参数。这是因为特定形状的特征是对应于不同晶格平面的唯一的一组和丰富的曲面。上述亚稳物质产物的加入与在动力学控制的反应路径下生成固相的可能性有关。该项目的主要任务是研究在高极性、非水的溶剂环境(离子液体)中亚稳产物的形成的影响。我们将专注于制备偏离最稳定形状(Wulff形态)的各向异性粒子。此外，我们还对溶剂在亚稳态晶体结构加入中的作用感兴趣，我们将通过将分子路线与材料合成相结合，并结合精细的现场研究来实现这种动力学控制条件。高活性有机金属前驱体将被我们用于制备重要的金属氧化物半导体材料，如氧化锌(ZnO)或氧化锰(MnxOy)。一个特别的挑战是产生包括不情愿的基团(例如氧化和还原)在一个分子中连接在一起的新型前体，目的是在接近环境或低于环境的极低温度下启动颗粒生长，或者通过诸如光的非常规触发来启动颗粒生长。我们将不仅通过对最终材料的详细分析，而且通过以现场模式进行的全面的X射线散射调查(小角和广角)，获得深厚的知识基础。所提出的过渡金属氧化物的优点是，与有机离子液体环境相比，电子密度的对比足以执行高时空分辨率的散射。我们将发现粒子形成的非常早期的阶段，提出问题，例如形状和晶体结构的形成是在什么时候决定的。

It is widely known from chemistry that the energy of transient states may be affected decisively by a surrounding solvent, so is the outcome of a chemical reaction. Also in materials science, one could interpret nanosized seeds as transient states for the generation of shaped particles or of phases with alternative crystal structure. In both cases, one is often interested in thermodynamically less favored (metastable) products, respectively unusual shapes or polymorphs. Besides crystal structure, also shape of a crystal is an important parameter determining its properties. This is, because a particular shape is characterized by a unique set and abundance of surfaces corresponding to different lattice planes. The accession of the mentioned, metastable materials products is linked to the possibility to generate the solid phase under kinetically controlled reaction pathways.The main task of the project is the investigation of the effects in highly polar, non-aqueous solvent environments (ionic liquids) with regards to the formation of metastable products. We will focus on the preparation of anisotropic particles deviating from the most stable shape (Wulff morphology). Furthermore, we are also interested in the role of the solvent concerning accession of metastable crystal structures.We will achieve such kinetically controlled conditions by interfacing molecular routes with materials synthesis, combined with refined in-situ investigations. Highly reactive, organometallic precursors will be used by us for the preparation of important metal oxide semiconductor materials like zinc oxide (ZnO) or manganese oxide (MnxOy). A particular challenge is the generation of novel precursors comprising reluctant groups (e.g. oxidizing and reducing) joined together in one molecule for the purpose of initiating particle growth either at very low temperatures near ambient or below, or initializing it by a non-conventional trigger such as light. A profound base of knowledge will be acquired by us, not only by a detailed analysis of the final materials, but also by comprehensive X-ray scattering investigations (small and wide angle) conducted in an in-situ mode. The advantage of the proposed transition metal oxides is that the contrast in electron density compared to the organic, ionic liquid environment is sufficient for performing scattering with a high tempospatial resolution. We will spot the very early stages of particle formation, raising the question at which point for instance formation of shape and crystal structure is determined.