Atomic Manipulation at Room Temperature

用扫描隧道显微镜(STM)进行原子操作是纳米技术的极限。到目前为止，这些实验通常是在低温下进行的，那里的热能足够低，原子不会随机移动。室温下的原子操控是一项新的运动。一种方法是通过化学键将分子锚定在表面，这样特定的靶基被呈现在STM的尖端，STM可以用作分子尺度的电子源。其目标是实现键选择性的分子操纵--纳米科学的前沿之一。然而，我们对这种操纵的机制(例如，电子和分子振动之间的耦合、能量耗散、对称规则等)的理解还处于初级阶段。这个项目的目的是在我们去年发表在《自然》杂志上的先前工作的基础上，在精心选择的分子体系中，在室温下研究单分子激发和与STM的键选择解离。在氯苯和相关的多氯联苯(PCB)分子家族的情况下，我们将测试我们提出的C-Cl键的双电子解离模型，该模型涉及对称性破坏，通过振动激发将原本不相连的(正交)分子轨道耦合在一起。多氯联苯对环境有害，我们可能会在这个过程中揭示如何分解它们。在选择代表S-S(二硫化物)基团的小分子的情况下，我们将研究电荷注入键的稳定性，共振形成可能出现的竞争(非绝热)动力学通道，以及S-S键裂变的机制。这与生物分子，特别是蛋白质对电离辐射(产生低能电子)的反应有关，因为折叠蛋白质中的不同链通常通过半胱氨酸氨基酸之间的S-S键连接。我们最近的实验已经建立了伯明翰小组，在世界领先的原子操纵小组之一。目前拨款提案的目的是在此基础上进行新一代高冲击性、室温下的扫描隧道显微镜操作实验，旨在将这项工作推向下一阶段。

Atomic manipulation with the scanning tunneling microscope (STM) is the extreme limit of nanotechnology. The experiments to date have generally been done at low temperatures, where the thermal energy is low enough that the atoms do not move around randomly. Atomic manipulation at room temperature is a new ball game. One approach is to anchor a molecule to the surface through a chemical bond, such that a particular target group is presented to the tip of the STM, which can be used as a molecular-scale source of electrons. The aim is to achieve bond-selective molecular manipulation - one of the frontiers of nanoscale science. Our understanding of the mechanisms of such manipulation (e.g., coupling between the electrons and the vibrations of the molecule, energy dissipation, symmetry rules, etc) is however in its infancy. The aim of this project is to investigate single molecule excitation and bond-selective dissociation with the STM, at room temperature, in carefully selected molecular systems, building on our previous work published in Nature last year. In the case of chlorobenzene and the related family of polychlorinated biphenyl (PCB) molecules, we will test a model we proposed for two-electron dissociation of the C-Cl bond, which involves symmetry-breaking, by vibrational excitation, which couples together otherwise disconnected ( orthogonal ) molecular orbitals. PCB's are environmentally harmful and we may in the process cast some light on how to break them down.In the case of small molecules chosen to present the S-S (disulphide) group, we will investigate the stability of the bond to charge injection, the competing ( non-adiabatic ) dynamical channels expected to arise as a result of resonance formation and the mechanism of S-S bond fission. This is relevant to the response of biological molecules, notably proteins, to ionising radiation (which generates low energy electrons), since different chains in a folded protein are often connected by S-S bonds between cysteine amino acids.Our recent experiments have established the Birmingham group amongst the leading atomic manipulation groups in the world. The purpose of the present grant proposal is to build on this foundation with a new generation of high impact, room temperature STM manipulation experiments designed to take the work on to the next level.