Molecular UHV-FTIR studies of adsorbate covered TiO2-microparticle surfaces

该项目旨在通过基于AFM和光谱技术的吸附物结构的分子控制研究颗粒和氧化物基材之间的接触力，这些结构涉及取向，厚度和流动性。作为模型系统，SiO2和TiO 2将被用来作为他们的表面改性是高度感兴趣的颗粒粉末的流动properties.The方法是基于这样的假设，即超真空（UHV），也干净的液相允许调整颗粒的界面化学没有环境污染的影响。此外，AFM胶体探针技术作为一种力分析方法允许在两种介质中的这种界面结构上的相互作用的影响的量化在接触区中的particles.As有机吸附有机膦酸将被使用，因为它们是大的兴趣考虑颗粒的表面性质的定制，并使不同的排序和化学功能的单层的制备。水在裸露表面或化学改性表面上的吸附是在界面处进行的，以消除真空或有机液相。超高真空分析装置包括用于分析吸附物化学的X射线光电子能谱仪（XPS）和用于测量裸露表面和吸附物覆盖表面上的接触力的超高真空原子力显微镜（UHV-AFM）。一个特别感兴趣的是作为化学性质和温度的函数的吸附层的流动性和排序。通过大气原子力显微镜的毛细管桥的形成及其对接触力作为表面化学和温度的函数的影响进行了研究。为了避免大气吸附物的影响，实验将在非极性有机相中进行，并控制水的活性。因此，在亲水性界面处，不同量的水将可用于涉及毛细管桥的冰状水层的温度依赖性相互作用。通过原位FTIR光谱和原位表面等离子体共振，这些水层的特征在于它们的厚度和结构。

The project aims at the study of contact forces between particles and oxidic substrates based on the molecular control of the adsorbate structure concerning the orientation, thickness and mobility via AFM based and spectroscopic techniques. As model systems, SiO2 and TiO2 will be used as their surface modification is of high interest for the flow properties of particle powders.The methodology is based on the hypothesis that ultrahigh vacuum (UHV) and also clean liquid phases allow for the adjustment of the interfacial chemistry of particles without the influence of environmental contaminations. Furthermore the AFM colloidal probe technique as a force analytical method allows in both media the quantification of the influence of this interface structure on the interaction in the contact zone of the particles.As organic adsorbates organophosphonic acids will be used, as they are of large interest for the tailoring of surface properties of the considered particles and enable the preparation of monolayers of different ordering and chemical functionality. The adsorption of water on bare or chemically modified surfaces is done at the interface to ultrahigh vacuum or an organic liquid phase.The UHV analytical setup includes an X-ray photoelectron spectrometer (XPS) for the analysis of the adsorbate chemistry and an UHV-AFM which allows the measurement of contact forces on bare and adsorbate covered surfaces. A particular interest is the mobility and ordering of the adsorbate layers as a function of the chemical properties and temperature. By means of atmospheric AFM the formation of capillary bridges and their influence on contact forces as a function of surface chemistry and temperature is investigated. To avoid the influence of atmospheric adsorbates, the experiments will be performed in an apolar, organic phase with a controlled activity of water. Hence at hydrophilic interfaces different amounts of water will be available for the temperature dependent interaction involving ice-like water layers of capillary bridges. Via in-situ FTIR spectroscopy and in-situ surface plasmon resonance these water layers will be characterized concerning their thickness and structure.