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Triggering, Controlling and Imaging Chemical Reactions at the Single-Molecule Level by Electron Beam

通过电子束触发、控制和成像单分子水平的化学反应

基本信息

批准号：
EP/R024790/1
负责人：
Andrei Khlobystov
金额：
$ 134.97万
依托单位：
University of Nottingham
依托单位国家：
英国
项目类别：
Fellowship
财政年份：
2018
资助国家：
英国
起止时间：
2018 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=EP%2FR024790%2F1
关键词：
Triggering Controlling Imaging Chemical Reactions

项目摘要

How do we know that molecules react in one way rather than another? In a given experiment, we study the reactions of large ensembles of molecules (billions of billions or more) that exist in different states and possess different kinetic energies, colliding with each other in a chaotic manner. Even in an ideal case, a reaction observed in a laboratory experiment by ensemble-averaging analytical techniques, such as spectroscopy or diffraction, can only support rather than confirm a proposed mechanism, as these macroscopic measurements are unable to rule out that an alternative atomistic mechanism may also exist that results in the same macroscale observation. In practice, definitive information about the mechanisms of intermolecular reactions can be provided only by a direct observation at the single-molecule level of the reactants transforming into products over time. In this context, scanning probe microscopy (SPM) methods have recently shed important light on the atomic structures of both the intermediates and products of chemical reactions; however, SPM critically lacks time resolution due to the scanning nature of AFM/STM and the fact that the molecules must be 'activated' by a stimulus, such as heat, during which the molecules remain unobserved, thus introducing the need for averaging information over an ensemble of species (albeit much smaller than in the bulk measurement). Transmission electron microscopy (TEM) offers unique opportunities for intermolecular reactions, very different, yet highly complementary, to SPM and gas-phase molecular spectroscopy. Using the three principles of ChemTEM: (i) physical entrapment and confinement of individual molecules in nano test tubes; (ii) direct momentum transfer from the incident electron beam to atoms; (iii) stop-frame filming of chemical bond dissociation and formation in direct space at the single-molecule level, this EPSRC project will address the challenge of simultaneous triggering and imaging of reaction pathways - from reactants via intermediates to products. The molecules constrained in two dimensions, for example in a nanotube, while having the third dimension free for chemistry, will be manipulated by the electron beam and imaged as they react with each other. In this way, the chemist has the individual molecules on an 'operating table' as it were, ready to be dissected and studied with atomic-level precision. The principles and methodology of ChemTEM developed in this project have the potential to become an imaging and analytical tool for molecular reactions, complementing and bolstering current spectroscopy, diffraction and SPM methods. ChemTEM will image reaction pathways in direct space at the single-molecule level and will enable the elucidation of reaction mechanisms of important chemical processes, such as C-C bond formation and dissociation, dehydrogenation and polycondensation reactions, leading to the improved preparative synthesis of high-value materials and the design of alternative catalysts. In addition, ChemTEM has great potential for the discovery of entirely new types of chemical reactions that can transform not only the way we study molecules but also launch a new wave of research in synthetic chemistry, which currently relies on a relatively small number of reaction types.

我们怎么知道分子以一种方式而不是另一种方式反应？在给定的实验中，我们研究了大量分子（数十亿或更多）的反应，这些分子以不同的状态存在并具有不同的动能，以混乱的方式相互碰撞。即使在理想的情况下，在实验室实验中通过整体平均分析技术（如光谱学或衍射）观察到的反应也只能支持而不是证实所提出的机制，因为这些宏观测量无法排除可能存在导致相同宏观观察的替代原子机制。在实践中，关于分子间反应机制的确定性信息只能通过在反应物随时间转化为产物的单分子水平上的直接观察来提供。在这方面，扫描探针显微镜（SPM）方法最近揭示了重要的光的原子结构的中间体和产品的化学反应;然而，由于AFM/STM的扫描性质以及分子必须被刺激（例如热）“激活”的事实，SPM严重缺乏时间分辨率，在此期间分子保持未观察到，因此引入了对物质集合上的平均信息的需要（尽管比整体测量小得多）。透射电子显微镜（TEM）为分子间反应提供了独特的机会，与SPM和气相分子光谱非常不同，但高度互补。利用ChemTEM的三个原理：（i）单个分子在纳米试管中的物理捕获和限制;（ii）从入射电子束到原子的直接动量转移;（iii）在单分子水平上直接空间中化学键解离和形成的停帧拍摄，这个EPSRC项目将解决同时触发和成像反应途径的挑战-从反应物到中间体到产物。在两个维度上被限制的分子，例如在纳米管中，同时具有不受化学影响的第三维，将被电子束操纵并在它们彼此反应时成像。通过这种方式，化学家将单个分子放在“手术台”上，准备以原子级的精度进行解剖和研究。该项目开发的ChemTEM的原理和方法有可能成为分子反应的成像和分析工具，补充和支持当前的光谱学，衍射和SPM方法。ChemTEM将在单分子水平上直接空间成像反应途径，并将能够阐明重要化学过程的反应机理，如C-C键的形成和解离，脱氢和缩聚反应，从而改进高价值材料的制备合成和替代催化剂的设计。此外，ChemTEM在发现全新类型的化学反应方面具有巨大的潜力，这些反应不仅可以改变我们研究分子的方式，还可以引发合成化学研究的新浪潮，目前合成化学依赖于相对较少的反应类型。