Characterisation of Metal Nanoclusters and Catalytic Mechanisms by Microwave Spectroscopy

物体旋转的速度取决于它的质量和质量在物体中的分布方式。因此，当有人骑在边缘时，很难设置一个迂回转弯，但如果那个人站在中间，就容易了。让飞盘旋转很容易，但让标枪翻转很难。这些观测结果是质量、几何结构和惯性之间关系的结果。同样的关系允许通过测量分子的旋转来研究分子的结构。微波光谱学的工作原理是使分子旋转，然后观察它们旋转的速度。给定的分子形状更像飞盘还是标枪？该技术还可用于确定原子在分子内的排列方式，并精确测量键间的键距和角度。它可以告诉我们一个分子是柔性的还是刚性的。它可以告诉我们电荷是如何分布的，告诉我们化学键的强度和性质。在一个新的应用中，我建议使用微波光谱学中的一种新工具来确定反应是否在所选金属纳米团簇的表面上催化。开发更高效、选择性和绿色的催化剂是现代化学研究的一个关键挑战。催化剂通常用于加速具有商业意义的化学反应和过程。工业利用固体金属提供的表面环境来催化各种化学产品、材料和食品的生产。例如，人造黄油是使用镍金属作为催化剂生产的。研究人员已经描述了如何将金属原子的纳米团簇支撑在表面上，成为高效的催化剂。已知这些单元的大小和拓扑结构（表面的分子景观）对其催化性能具有深远的影响。该提案旨在尽可能小的尺度上对金属纳米团簇催化的分子机制提供基本信息。已知一氧化碳会使催化材料中毒，降低其效率。吸附一氧化碳的金属纳米团簇将是研究的目标之一。H2O和CO在工业上重要的催化反应中产生H2和CO2，该催化反应是氢燃料的有用来源（水煤气变换反应）。我将研究这种反应是否可以在非常小的金属纳米团簇上发生，如果可以，它的效率是否是团簇大小的函数。传统的Balle-Flygare傅里叶变换微波（FTMW）光谱仪具有窄的1 MHz带宽，并且不适合快速收集数据。本研究将利用21世纪世纪最新的数位技术，建构一种新颖的啁啾脉冲傅立叶变换微波光谱仪。新的CP-FTMW仪器将是宽带的，允许同时收集11 GHz频率范围内的数据。由于可以同时监测气体样品中许多不同成分的浓度，该仪器最终可能在分析科学中找到应用。它也将非常适合探测许多生物重要分子的微波光谱。

The speed at which an object rotates depends upon its mass and the way that mass is distributed in the object. Thus, it is harder to set a roundabout turning when somebody is riding at the edge but easier if that person stands right in the middle. It is easy to set a frisbee spinning but hard to flip a javelin end-over-end. These observations are a consequence of the relationship between mass, geometrical structure and inertia. The same relationship allows study of the structure of a molecule through measurements of its molecular rotation. Microwave spectroscopy works by causing molecules to spin and then seeing how fast they rotate. Is a given molecule shaped more like a frisbee or a javelin? The technique can also be used to determine how atoms are arranged within a molecule and to accurately measure bond distances and angles between bonds. It can tell us whether a molecule is flexible or rigid. It can say how charge is distributed, telling us about the strength and nature of chemical bonds. In a novel application, I propose to use a new tool in microwave spectroscopy to determine whether reactions are catalysed on the surface of selected metal nanoclusters. The development of more efficient, selective and greener catalysts is a key challenge of modern research in chemistry. Catalysts are often used to accelerate chemical reactions and processes of commercial significance. Industry employs the surface environment provided by solid metals to catalyse the manufacture of a wide variety of chemical products, materials and foods. For example, margarine is produced using nickel metal as a catalyst. Researchers have already described how nanoclusters of metal atoms supported on surfaces can be highly effective catalysts. It is known that the size and topology (molecular landscape of the surface) of these units can have a profound influence on their catalytic properties. This proposal seeks to contribute fundamental information on the molecular mechanisms of catalysis on metal nanoclusters on the smallest possible scale. Carbon monoxide is known to poison catalytic materials, reducing their efficiency. Metal nanoclusters with adsorbed carbon monoxide will be one target of studies. H2O and CO yield H2 and CO2 in an industrially-important catalysed reaction that is a useful source of hydrogen fuel (the water gas shift reaction). I will study whether this reaction can occur on very small metal nanoclusters, and if so, whether its efficiency is a function of cluster size. Conventional Balle-Flygare Fourier transform microwave (FTMW) spectrometers possess a narrow, 1 MHz bandwidth and are unsuitable for collecting data rapidly. The proposed research will exploit the latest 21st century digital technology for the construction of a novel chirped pulse Fourier transform microwave (CP-FTMW)spectrometer. The new CP-FTMW instrument will be broadband and allow the collection of data over an 11 GHz frequency range simultaneously. Given that it will be possible to monitor the concentration of many different components in a gas sample simultaneously, this instrument may ultimately find applications in analytical science. It will also be perfectly suited to probe the microwave spectra of many biologically-significant molecules.