Department of Applied Physics and Applied Mathematics, Columbia University, New York, New York 10027, USA.
J Am Chem Soc. 2012 Mar 7;134(9):4003-6. doi: 10.1021/ja211590d. Epub 2012 Feb 24.
We use a modified conducting atomic force microscope to simultaneously probe the conductance of a single-molecule junction and the force required to rupture the junction formed by alkanes terminated with four different chemical link groups which vary in binding strength and mechanism to the gold electrodes. Molecular junctions with amine, methylsulfide, and diphenylphosphine terminated molecules show clear conductance signatures and rupture at a force that is significantly smaller than the measured 1.4 nN force required to rupture the single-atomic gold contact. In contrast, measurements with a thiol terminated alkane which can bind covalently to the gold electrode show conductance and force features unlike those of the other molecules studied. Specifically, the strong Au-S bond can cause structural rearrangements in the electrodes, which are accompanied by substantial conductance changes. Despite the strong Au-S bond and the evidence for disruption of the Au structure, the experiments show that on average these junctions also rupture at a smaller force than that measured for pristine single-atom gold contacts.
我们使用改良的导电原子力显微镜，同时探测单分子结的电导和断开由四个不同化学连接基团终止的烷烃形成的结所需的力，这些基团在与金电极的结合强度和机制方面有所不同。带有胺、甲基硫醚和二苯基膦基团的分子结表现出明显的电导特征，并在明显小于测量的 1.4 nN 断开单原子金接触所需力的情况下断裂。相比之下，用可以与金电极共价结合的硫醇终止的烷烃进行的测量表现出与其他研究的分子不同的电导和力特征。具体而言，强 Au-S 键可以导致电极的结构重排，这伴随着显著的电导变化。尽管存在强的 Au-S 键和 Au 结构破坏的证据，但实验表明，这些结的平均断裂力也小于测量的原始单原子金接触的力。
