From birth to growth of metastable metal oxides in ionic liquids

从化学中众所周知，过渡态的能量可能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，人们可以将纳米尺寸的种子解释为用于生成成形颗粒或具有替代晶体结构的相的瞬态。在这两种情况下，人们通常对化学上不太有利的（亚稳）产物感兴趣，分别是不寻常的形状或多晶型物。除了晶体结构之外，晶体的形状也是决定其性质的重要参数。这是因为特定形状的特征在于对应于不同晶格平面的表面的唯一集合和丰富度。上述亚稳态材料产品的加入与在动力学控制的反应途径下生成固相的可能性有关。该项目的主要任务是研究高极性非水溶剂环境（离子液体）对亚稳态产品形成的影响。我们将专注于偏离最稳定形状（武尔夫形态）的各向异性颗粒的制备。此外，我们还对溶剂在亚稳晶体结构中的作用感兴趣。我们将通过将分子途径与材料合成相结合，结合精细的原位研究，实现这种动力学控制条件。高活性的有机金属前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新的前体，其包含在一个分子中连接在一起的不情愿基团（例如氧化和还原），目的是在接近环境温度或低于环境温度的非常低的温度下引发颗粒生长，或通过非常规的触发剂如光来初始化颗粒生长。我们不仅通过对最终材料的详细分析，而且还通过以原位模式进行的全面X射线散射调查（小角度和广角），获得了深厚的知识基础。所提出的过渡金属氧化物的优点在于，与有机离子液体环境相比，电子密度的对比度足以进行具有高时空分辨率的散射。我们将发现粒子形成的早期阶段，提出一个问题，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.