Department of Chemistry, Graduate School of Science and Engineering, Tokyo Institute of Technology, Ookayama, Meguro-ku, Tokyo 152-8551, Japan.
Small. 2012 Mar 12;8(5):726-30. doi: 10.1002/smll.201102075. Epub 2012 Jan 5.
An electronic conductance with small fluctuations, which is stipulated in single-molecule junctions, is necessary for the precise control of single-molecule devices. However, the suppression of conductance fluctuations in conventional molecular junctions is intrinsically difficult because the fluctuations are related to the contact fluctuations and molecular motion. In the present study involving experimental and theoretical investigations, it is found that covering a single π-conjugated wire with an α-cyclodextrin molecule is a promising technique for suppressing conductance fluctuations. The conductance histogram of the covered molecular junction measured with the scanning tunneling microscope break-junction technique shows that the conductance peak for the covered junction is sharper than that of the uncovered junction. The covering technique thus has two prominent effects: the suppression of intramolecular motion, and the elimination of intermolecular interactions. Theoretical calculations of electronic conductance clearly support these experimental observations.
在单分子结中，存在一种电子电导的小涨落，这对于精确控制单分子器件是必要的。然而，由于电导涨落与接触涨落和分子运动有关，传统的分子结中对电导涨落的抑制本质上是困难的。在本研究中，通过实验和理论研究发现，用α-环糊精分子覆盖单个π共轭线是抑制电导涨落的一种很有前途的技术。用扫描隧道显微镜断键技术测量的覆盖分子结的电导直方图表明，覆盖结的电导峰比未覆盖结的更尖锐。因此，覆盖技术具有两个突出的效果：抑制分子内运动，消除分子间相互作用。电子电导的理论计算清楚地支持了这些实验观察。
