New insights into complex molecule-surface interactions through local structure determination

通过局部结构测定对复杂分子-表面相互作用的新见解

• 批准号: EP/D034329/1
• 负责人: David Woodruff
• 金额: $ 37.12万
• 依托单位: University of Warwick
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2006
• 资助国家: 英国
• 起止时间: 2006 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=EP%2FD034329%2F1
• 关键词: New; insights; into; complex; molecule

Solids interact with their surroundings through their surfaces, so it is the surface properties which dominate the reactivity of solids as catalysts, their response to corrosive environments, and in the way they can bond to other solids to make electronic devices. Knowledge of the structure of these surfaces (the relative positions of the atoms and molecules) is the key to most attempts to understand the chemical and electronic properties. This project seeks to use one particular specialised method, scanned-energy mode photoelectron diffraction (PhD), to investigate a series of specific structural problems selected to give insight into distinct classes of surface processes. The special features of this method are that it can provide the local geometry of specific atoms within a molecule bonded to a surface, distinguishing atoms of different elements and atoms of the same element in different local bonding environments. This means that one can tackle problems of increasing complexity and thus of increasing relevance to 'real world' surface processes. For example, the interaction with surfaces of large biological molecules, such as proteins and DNA, is potentially important in medical screening for disease, and in ensuring the body does not reject medical implants (e.g. artificial hip joints).These molecules are far too large for their surface interaction to be probed at an atomic scale with any available methods. However, these molecules interact with surfaces through key molecular components, and while even these 'small' molecules present a major challenge for surface structure determination, use of the PhD method should allow the local bonding structure to be determined; one objective of this work is thus to understand the interaction of surfaces with the simplest of these component molecules. Other problems to be addressed mostly involve simpler molecular and atomic adsorbates, but more complex surfaces. In particular, while most surface science experiments have been performed on metal and semiconductor surfaces, a very important class of materials with surface chemical properties of practical importance are oxides, but these are mostly insulators and prove difficult to study by standard methods. In particular, there is a dearth of structural information on oxide surfaces. Recent work using the PhD technique to probe the surfaces of ultra-thin oxide films has proved very successful in obtaining adsorption structures on model surfaces, some of the results highlighting failures in current theoretical understanding of these materials. A significant extension of this work to make inroads into our understanding of molecule-oxide surface interactions is envisaged as a key ingredient of this research programme.The project also aims to explore an important novel extension of the technique to allow structure determination under 'real' chemical reaction conditions. The way atoms and molecules interact with surfaces underpins the hugely important area of heterogeneous catalysis, but the practical application of this technology, such as the clean-up of car exhaust gases in the car's catalytic converter, operate around one atmosphere of pressure. Most methods to probe surface properties, however, have been developed to work only in very good ('ultra-high') vacuum conditions; lowering the pressure of the gas (air) surrounding a surface lowers the rate at which molecules arrive from the air and contaminate the surface, and to ensure this process is slow enough to keep a sample clean for an hour or so, one needs to work in a pressure of about one million-billionth of an atmosphere (comparable to, but somewhat higher than, the pressure in outer space). Finding a way to obtain local structural information at pressures closer to those of 'real' reactions is thus an important goal, and this proposal seeks to explore one possible method to achieve this in by a method capable of unravelling the complexity of such a surface.

固体通过其表面与周围环境相互作用，因此表面性质决定了固体作为催化剂的反应性，它们对腐蚀性环境的反应，以及它们与其他固体结合以制造电子设备的方式。了解这些表面的结构（原子和分子的相对位置）是大多数试图理解化学和电子性质的关键。该项目旨在使用一种特殊的专门方法，扫描能量模式光电子衍射（PhD），来研究一系列特定的结构问题，以深入了解不同类别的表面过程。这种方法的特点是它可以提供键合到表面上的分子内特定原子的局部几何形状，区分不同元素的原子和不同局部键合环境中的相同元素的原子。这意味着人们可以解决越来越复杂的问题，从而增加与“真实的世界”表面过程的相关性。例如，与大生物分子（如蛋白质和DNA）表面的相互作用在疾病的医学筛查中以及在确保身体不排斥医疗植入物（例如人工髋关节）方面具有潜在的重要性。这些分子对于它们的表面相互作用来说太大了，无法用任何可用的方法在原子尺度上进行探测。然而，这些分子通过关键的分子组分与表面相互作用，而即使是这些“小”分子的表面结构测定提出了一个重大挑战，使用博士方法应允许本地键合结构被确定;这项工作的一个目标，因此，了解这些组件分子中最简单的表面的相互作用。其他要解决的问题主要涉及更简单的分子和原子吸附物，但更复杂的表面。特别是，虽然大多数表面科学实验都是在金属和半导体表面上进行的，但具有实际重要性的表面化学性质的一类非常重要的材料是氧化物，但这些材料大多是绝缘体，难以通过标准方法进行研究。特别是，氧化物表面的结构信息缺乏。最近的工作使用博士技术探测超薄氧化膜的表面已被证明是非常成功的获得模型表面上的吸附结构，一些结果突出了这些材料的当前理论理解的失败。一个显着的扩展这项工作，使我们的理解的分子-氧化物表面相互作用的进展设想作为本研究programme.The项目的关键组成部分，还旨在探索一个重要的新的扩展技术，使结构测定下的“真实的”化学反应条件。原子和分子与表面相互作用的方式是多相催化这一非常重要领域的基础，但这项技术的实际应用，如在汽车催化转化器中清理汽车尾气，是在一个大气压下进行的。然而，大多数探测表面性质的方法都是在非常好的条件下才能工作的。（“超高”）真空条件;降低表面周围的气体（空气）的压力降低了分子从空气到达并污染表面的速率，并且为了确保该过程足够慢以保持样品清洁一小时左右，人们需要在大约百万分之一大气压的压力下工作（与外层空间的压力相当，但略高于外层空间的压力）。因此，找到一种方法，以获得当地的结构信息的压力更接近那些“真实的”反应是一个重要的目标，这个建议旨在探索一种可能的方法来实现这一点，通过一种方法能够解开这样的表面的复杂性。