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Force-induced molecular dissociation at surfaces via a local probe

通过局部探针在表面力诱导分子解离

基本信息

批准号：
242887252
负责人：
Dr. Alexander Saywell
金额：
--
依托单位：
School of Physics and Astronomy
依托单位国家：
德国
项目类别：
Research Grants
财政年份：
2013
资助国家：
德国
起止时间：
2012-12-31 至 2014-12-31
项目状态：
已结题

来源：
https://gepris.dfg.de/gepris/projekt/242887252?language=en
关键词：
Force induced molecular dissociation surfaces

项目摘要

The dissociation of chemical bonds is a fundamental process in all chemical reactions. Scanning tunnelling microscopy (STM) has been used to induce the breaking of single covalent bonds within a molecule via tunnelling electrons. However, it has never been attempted to break a chemical bond within a molecule not via tunnelling electrons but only by applying a force with a local probe. The main objective of this project is to explore whether it is possible to induce such a process within an individual adsorbed molecule by using STM and atomic force microscopy (AFM), which in addition to atomically resolved imaging allows the study of short-range chemical forces between the molecule and the probe as a function of molecule-probe separation. A combination of force-spectroscopy and topographical imaging will allow characterisation of the forces and potential energies during the probe-molecule interaction and the structure of the molecule before and after the applied force with very high resolution.As it has previously been demonstrated that carbon-halogen (C-X) bonds in organic molecules may be cleaved selectively by other methods (e.g. thermal activation - facilitating on-surface synthesis processes), we will focus on breaking such a carbon-halogen covalent bond. Within this project a molecular species containing a reactive C-X moiety will be deposited on a surface held under ultra-high vacuum (UHV) conditions, a metallic probe will be approached towards the C-X bond, and the forces between the molecule and the probe measured. The experiments will (1) ascertain whether a C-X bond within an individual molecule adsorbed on a substrate can be broken by applying a force at low temperatures (120K) and, (2) measure the forces present during the probe-molecule interaction and thus provide information on the potential energy landscape. The breaking of a C-X bond within a molecule that is adsorbed on a surface is typically driven by the interaction between the adsorbed molecule and a metallic substrate (often Cu, Ag, or Au); i.e. a catalytically active environment. Additional experiments will therefore (3) study the dependence of the measured force on the chemical properties of the system by changing the metal atoms at the probe apex (Cu, Ag, or Au) or by changing the halogen species within the molecule (Br or I). Furthermore, as in conventional synthetic processes where thermal energy often initiates the reaction, we will (4) study the effect of the substrate temperature on the force-induced bond dissociation process.This novel approach to inducing and studying molecular bond dissociation by interatomic forces has not previously been explored, and potentially offers an atomic-scale insight into the role of the chemical environment and temperature within this dissociation process.

化学键的解离是所有化学反应中的一个基本过程。扫描隧道显微镜(STM)已被用来通过隧道电子诱导分子内单一共价键的断裂。然而，从来没有人试图不通过隧穿电子来破坏分子中的化学键，而是仅仅通过使用局部探测器施加力来打破分子内的化学键。该项目的主要目标是探索是否有可能通过使用STM和原子力显微镜(AFM)在单个吸附分子中诱导这样的过程，除了原子分辨成像外，原子力显微镜还允许研究分子与探针之间的短程化学力作为分子-探针分离的函数。力光谱和形貌成像的结合将能够以很高的分辨率表征探针-分子相互作用过程中的力和势能以及作用力前后的分子结构。由于以前已经证明有机分子中的碳-卤键可以被其他方法选择性地断裂(例如，热激活-促进表面合成过程)，我们将重点研究打破这种碳-卤共价键。在这个项目中，一个含有活性C-X部分的分子物种将被沉积在超高真空(UHV)条件下保持的表面上，一个金属探针将接近C-X键，并测量分子和探针之间的力。这些实验将(1)确定吸附在底物上的单个分子内的C-X键是否可以通过在低温(120K)下施加力来破坏，(2)测量探针-分子相互作用过程中存在的力，从而提供势能图景的信息。被吸附在表面上的分子内C-X键的断裂通常是由被吸附的分子与金属衬底(通常是铜、银或金)之间的相互作用所驱动的，即催化活性环境。因此，额外的实验将(3)通过改变探针尖端的金属原子(铜、银或金)或通过改变分子中的卤素物种(溴或碘)来研究所测力对体系化学性质的依赖性。此外，在热能经常引发反应的传统合成过程中，我们将(4)研究衬底温度对力诱导键解离过程的影响。这种通过原子间作用力诱导和研究分子键解离的新方法以前从未被探索过，并且潜在地提供了一个原子尺度的洞察化学环境和温度在解离过程中的作用。