Surface electronic structure, solvation properties of simple atoms and ions studied by electron spectroscopy and density functional theory

详细了解离子液体(IL)的表面结构以及原子、分子和团簇的溶剂化对于了解它们的性质是必不可少的，以便能够改进这些材料的性能，特别是在界面化学和电化学应用中作为“绿色溶剂”的性能。更重要的方面是对可能具有表面活性的杂质的分析，与分子的相互作用，特别是那些在操作条件下存在的分子，以及由于辐射诱导效应或等离子体条件而引起的它们的修饰。与这些方面相关的是，这些交互作用可能导致的降级对许多应用程序具有很高的相关性。对于某些方法，金属或半导体的溶液及其可能的表面浓缩是非常有趣的。此外，在ILS生产纳米粒子的情况下，分析特定选择的条件(IL、操作条件、溶剂化物种)对形成产物的影响可能是非常重要的。为了加深我们对上述主题的基本理解，并为我们的合作伙伴提供关于表面化学和电子结构的详细信息，我们计划结合光电子能谱和亚稳态碰撞电子能谱(MIES)，并可能伴随着其他实验方法(质谱学、离子散射和振动光谱)进行第一原理计算。由于其极端的表面敏感性，MIES提供了关于所研究的凝聚物质边缘的信息，例如最顶部表层中物种的波函数的尾部。随着XPS、UPS和MIES的表面敏感度越来越高，XPS和UPS与MIES的结合是获得表面电子结构详细信息的非常强大的工具。如果对数据的解释是基于可靠的理论计算，这一点尤其成立。此外，我们的实验技术是对Steinrück教授小组应用的技术的补充，该小组也在研究表面性质。与该小组现有的合作将继续下去。为了获得所需的关于近地表区域的信息，我们设立了一个工作方案，该方案与SPP内的其他研究建议密切相关。将更详细地讨论以下问题：·将结合表面敏感实验方法和“第一性原理”计算来研究选定ILS的表面性质。这些离子液体尤其令人感兴趣：(I)作为模型液体的离子液体，用于阐明离子液体分子表面结构的基本性质。(Ii)我们的合作伙伴感兴趣的离子液体，它们应用它们来研究离子液体与等离子体相互作用下纳米粒子的生长(Janek教授，JLU gieüen教授和Endres教授，TU Clausthal)。(Iii)含有来自马尔堡大学Sundermeyer教授群的过渡金属的离子液体。对于所有这些离子液体，我们将彻底筛选它们在离子液体真空界面上的离子取向随温度的变化。将研究ILS的络合物和分子，以获得关于它们的溶剂化性质以及潜在的表面分离的信息。这些研究包括原子在IL膜上原位蒸发后的分析和合作伙伴提供的样品分析。·将研究ILS在环境条件影响下的变化，以获得关于降解效果和机理的重要信息。此外，将考虑光诱导效应，以确保我们数据的可靠性，并获得有关光刺激降解的信息。·我们将特别分析由我们的合作伙伴提供的金属和半导体颗粒的化学成分，以获得有关其特性和进一步调整其特性的可能性的重要信息。

Detailed knowledge of the surface structure of Ionic Liquids (IL) and the solvation of atoms, molecules and clusters appears indispensable for understanding their properties in order to be able to refine the performance of these materials, in particular as “green solvents”, in e.g. interfacial chemistry and electrochemical applications. Further important aspects are the analysis of impurities, which might be surface active, the interaction with molecules, in particular those present under operation conditions, and their modification due to radiation induced effects or plasma conditions. Related to these aspects, possible degradation caused by these interactions is of high relevance for many applications. For some of the approaches, the solution of metals or semiconductors and their possible surface enrichment are very interesting. Additionally, in case of nanoparticle production from ILs it might be of large importance to analyze the influence of the particular chosen conditions (IL, operating conditions, solvated species) on the formed products.In order to improve our fundamental understanding of the above mentioned topics and to provide detailed information on surface chemistry and electronic structure for our partners, we plan to apply a combination of photoelectron spectroscopies and Metastable Impact Electron Spectroscopy (MIES) with “first principles” calculations possibly accompanied by other experimental methods (mass spectroscopy, ion scattering and vibrational spectroscopy). Due to its extreme surface sensitivity MIES provides information on the rim of the condensed material under study, e.g. the tails of the wavefunctions of species in the very topmost surface layer. As XPS, UPS and MIES are increasingly surface sensitive, the combination of XPS and UPS with MIES is a very powerful tool for gaining detailed information on the surface electronic structure. This holds in particular, if the interpretation of the data is based on reliable theoretical calculations. Moreover, our experimental techniques are complementary to those applied by the group of Prof. Steinrück, which is also studying the surface properties. The existing collaboration with this group will be continued. In order to obtain the desired information about the near surface region, we have set up a working program that is, in addition, strongly interconnected to other research proposals within the SPP. In more detail the following questions will be addressed:• Surface properties of the selected ILs will be studied by combining surface-sensitive experimental methods and “first principles” calculations. In particular the following of ILs are of interest:(i) ILs which serve as model liquids to elucidate fundamental properties of the molecular surface structure of an ionic liquid.(ii) ILs of interest for our partners, which apply them to study the nanoparticle growth by the ILplasma-interaction (Prof. Janek, JLU Gießen and Prof. Endres, TU Clausthal).(iii) ILs containing transition metals from the group of Prof. Sundermeyer, Universität Marburg.For all these ILs we will thoroughly screen them for changes of the IL-ion-orientation at the ILvacuum interface with temperature.• The interaction of atoms, complexes and molecules with ILs will be studied to obtain information about their solvation properties as well as potential surface segregation. These studies include the analysis after in-situ evaporation of atoms onto IL films and the analysis of samples provided by partners.• Changes of ILs under the influence of environmental conditions will be studied to gain important information on degradation effects and mechanisms. In addition photo-induced effects will be considered in order to ensure the reliability of our data and to obtain information on photo-stimulated degradation.• Metal and semiconductor particles provided by our partners will be analyzed in particular with respect to the chemical composition in order to obtain important information on their properties and possibilities of further tuning their properties.