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: 2015
• 资助国家: 加拿大
• 起止时间: 2015-01-01 至 2016-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=587623
• 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机会来详细了解表面发生简单化学反应的方式。这个机会源于当代研究三个领域的融合：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）以及揭示复杂分子动力学的计算机模型的发展反应性遭遇（诺贝尔化学奖，2013）。 STM 允许实验者获得表面单分子的图像。反应动力学（由申请人和许多其他人开创的领域）是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。这三个场的结合首次提供了在表面观察单个试剂分子、跟踪它们被热、光或电子激活以及关联它们的初始和最终几何形状的机会。 “理论化学为我们提供了整部戏剧，”诺贝尔化学奖评选委员会主席在本周宣布分子建模化学奖时说道。 本提案的主题是一次绘制一个分子表面反应过程中分子运动的机会。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) 它特别配备了四个超高真空 STM，用于研究半导体和金属的良好表征表面的反应，以及 (2) 最近介绍并演示了它（在 5 篇发表的论文中）目前的授权期）从头算模型（“脉冲二态”，I2S，模型），作为负责转换试剂的分子运动序列的指南，观察其表面的几何形状通过 STM 转化为产品，并通过相同的方式观察其几何形状。 这项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——打破旧的键并形成新的键。反应动力学的基本问题是试剂如何接近、如何碰撞以及如何分离。这里提出的一种实验方法（在本报告期内，我们首先通过简单的化学反应进行了演示，然后进行了 STM）是在表面定位和对齐一对试剂，然后通过以下方式触发“表面对齐反应”（SAR）：分子对之一的激发。构成本提案一部分的其他实验方法包括通过表面电荷转移研究低温表面反应，以及通过比较振动与电子激发来研究反应动力学对试剂激发模式的依赖性。 这些实验及其相关理论具有明显的实用目的，正如本期研究报告的结果所证明的那样，因为制造纳米结构的进展将取决于我们对反应位置和结合的了解和控制能力表面上的产品。在此提交的材料中描述了一种强大的表面图案化方法“分子尺度压印”，该方法适用于半导体，并且（首次）也适用于金属。 NSERC 发现补助金通过培育影响深远的基础科学，为后续的变革性应用提供了最大的希望。