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，当有人在边缘骑行时，设置环形转弯比较困难，但如果该人正好站在中间，设置环形转弯就更容易了。让飞盘旋转很容易，但把标枪翻过来却很难。这些观测结果是质量、几何结构和惯性之间关系的结果。同样的关系可以通过测量分子的旋转度来研究分子结构。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？这项技术还可以用来确定原子在分子中的排列方式，并准确地测量键之间的键距离和角度。它可以告诉我们一个分子是柔性的还是刚性的。它可以说电荷是如何分布的，告诉我们化学键的强度和性质。在一个新的应用中，我提议使用微波光谱中的一种新工具来确定反应是否在选定的金属纳米团簇的表面上被催化。开发更高效、更有选择性、更绿色的催化剂是现代化学研究的关键挑战。催化剂经常被用来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制造各种化学产品、材料和食品。例如，人造黄油是用金属镍作为催化剂生产的。研究人员已经描述了负载在表面的金属原子纳米团簇如何成为高效催化剂。众所周知，这些单元的大小和拓扑结构(表面的分子景观)可以对它们的催化性能产生深远的影响。这项提议寻求在尽可能小的规模上提供关于金属纳米团簇上催化的分子机制的基本信息。众所周知，一氧化碳会毒害催化材料，降低它们的效率。吸附了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，这是氢燃料的有用来源(水煤气变换反应)。我将研究这个反应是否可以发生在非常小的金属纳米团簇上，如果是的话，它的效率是否是团簇大小的函数。传统的Balle-Flygare傅立叶变换微波(FTMW)光谱仪具有1 MHz的窄带宽，不适合快速采集数据。这项研究将利用21世纪最新的数字技术来构建一种新型的啁啾脉冲傅里叶变换微波(CP-FTMW)光谱仪。新的CP-FTMW仪器将是宽带的，并允许同时在11 GHz频率范围内收集数据。鉴于可以同时监测气体样品中许多不同组分的浓度，这种仪器最终可能会在分析科学中得到应用。它也将非常适合探测许多具有生物意义的分子的微波光谱。

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.