Reaction Dynamics At Surfaces, A-Molecule-At-A-Time

表面反应动力学，一次一个分子

• 批准号: RGPIN-2014-04136
• 负责人: Polanyi, John
• 金额: $ 13.84万
• 依托单位: University of Toronto
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2017
• 资助国家: 加拿大
• 起止时间: 2017-01-01 至 2018-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=632485
• 关键词: Reaction; Dynamics; Surfaces; Molecule; Time

This research proposes to exploit an opportunity which has arisen in recent years to obtain detailed understanding of the way in which simple chemical reactions take place at surfaces. The opportunity stems from the confluence of three fields of contemporary research: Scanning Tunneling Microscopy (STM) (Nobel Prize in Physics, 1986) experimental Reaction Dynamics (Nobel Prize in Chemistry, 1986) and the development of Computer Models revealing the molecular dynamics in complex reactive encounters (Nobel Prize in Chemistry, 2013). STM, allows the experimenter to obtain images of single molecules at surfaces. Reaction Dynamics (a field pioneered by the applicant with many others) is the experimental study of the molecular motions that give rise to chemical reaction. Computer modeling reveals the complex atomic and molecular motions that transform reagents into products. A combination of these three fields offers, for the first time, the opportunity to see individual reagent molecules at surfaces, follow their activation by heat, light or electrons, and correlate their initial and final geometries. "Theoretical chemistry provides us with the whole drama," said the Chair of the Chemistry Nobel Selection Committee in announcing the Chemistry award for molecular modeling, this week. The opportunity to map the molecular motions in the course of surface reactions, a-molecule-at-a-time, is the subject of the present proposal. This laboratory is well placed for studies of this type, since it combines experiment with computer-based theory. Specifically (1) it is equipped, exceptionally, with four Ultra-High Vacuum STM's for studies of reactions at the well-characterized surfaces of semi-conductors and metals, and (2) it has recently introduced and demonstrated (in five published papers from the present granting period) an ab initio model (the 'Impulsive Two-State', I2S, model) that serves as a guide to the sequence of molecular motions responsible for converting reagent, whose geometry at the surface is observed by STM, into products, whose geometry is observed by the same means. The purpose of the proposed work is to provide understanding at the molecular level of an event central to chemistry, as also to life, namely the ability of chemical reactions to convert one substance into another--breaking old bonds and forming new. The fundamental question of Reaction Dynamics is how reagents approach, how they collide, and how they separate. One experimental approach proposed here (first demonstrated by us for a simple chemical reaction followed by STM, in the present reporting period) is to position and align a pair of reagents at the surface, and then trigger 'Surface Aligned Reaction' (SAR) by excitation of one of the molecular pair. Other experimental approaches that form a part of this Proposal are studies of Low-Temperature Surface Reaction by charge-transfer from the surface, and Dependence of Reaction Dynamics on Mode of Reagent Excitation by comparing vibrational with electronic excitation. These experiments and their accompanying theories have an evident practical purpose, as demonstrated in results reported here from the current period of research, since progress in fabricating nano-structures will depend on our knowledge of, and ability to control, the location and binding of reaction products at surfaces. A powerful means to pattern surfaces, 'Molecular-Scale Imprinting', shown here to be applicable to semi-conductors and (for the first time) also to metals, is described in this submission. NSERC Discovery Grants by fostering far-reaching basic science offer the best possible hope for subsequent transformative applications.

这项研究旨在利用近年来出现的一个机会，详细了解表面发生简单化学反应的方式。这一机会源于当代研究的三个领域的融合：扫描隧道显微镜（STM）（诺贝尔物理学奖，1986年）实验反应动力学（诺贝尔化学奖，1986年）和计算机模型的发展揭示了复杂反应遭遇中的分子动力学（诺贝尔化学奖，2013年）。扫描隧道显微镜允许实验者获得表面单个分子的图像。反应动力学（申请人与许多其他人一起开创的领域）是对引起化学反应的分子运动的实验研究。计算机建模揭示了将试剂转化为产品的复杂原子和分子运动。这三个领域的结合首次提供了在表面看到单个试剂分子的机会，通过热，光或电子跟踪它们的活化，并将它们的初始和最终几何形状关联起来。“理论化学为我们提供了整个戏剧，”化学诺贝尔奖评选委员会主席在本周宣布分子建模化学奖时说。在表面反应过程中绘制分子运动图的机会，一次一个分子，是本提案的主题。该实验室非常适合此类研究，因为它将实验与基于计算机的理论相结合。具体来说，（1）它特别配备了四台超高真空STM，用于研究半导体和金属表面的反应，（2）它最近引进并证明了（在本授权期内发表的五篇论文中）从头算模型（“脉冲双态”，I2 S，模型），其用作负责将试剂转化为产物的分子运动序列的指导，所述试剂在表面的几何形状通过STM观察，其几何形状用同样的方法观察。拟议工作的目的是在分子水平上提供对化学以及生命的核心事件的理解，即化学反应将一种物质转化为另一种物质的能力-打破旧键并形成新键。反应动力学的基本问题是试剂如何接近，它们如何碰撞，以及它们如何分离。这里提出的一种实验方法（在本报告期间，我们首先证明了一个简单的化学反应，然后是STM）是在表面定位和对齐一对试剂，然后通过激发一个分子对来触发“表面对齐反应”（SAR）。其他实验方法，形成本建议的一部分是研究低温表面反应的电荷转移从表面，和反应动力学的依赖性的试剂激发模式，通过比较振动与电子激发。这些实验及其伴随的理论具有明显的实际目的，正如本文所报道的当前研究阶段的结果所表明的那样，因为制造纳米结构的进展将取决于我们对反应产物在表面的位置和结合的了解和控制能力。一个强大的手段来图案表面，“分子尺度印迹”，这里显示，适用于半导体和（第一次）也对金属，在此提交的描述。NSERC发现赠款通过促进深远的基础科学为随后的变革性应用提供了最好的希望。