Molecular Nanofabrication Group and ‡Inorganic Materials Science Group, Department of Science and Technology, MESA+ Institute for Nanotechnology, University of Twente , P.O. Box 217, 7500 AE Enschede, The Netherlands.
Langmuir. 2017 Sep 5;33(35):8614-8623. doi: 10.1021/acs.langmuir.6b03860. Epub 2017 Jan 9.
The effect of the distance between a β-cyclodextrin (βCD) host core and a conductive substrate on the electron-transfer rate of complexed guests as well as of free-diffusing electrochemically active probes has been studied. First we have evaluated a set of short-tethered βCD adsorbates bearing different anchoring groups in order to get a reliable platform for the study of short-distance electron transfer. An electrochemically active trivalent guest was immobilized on these host monolayers in a selective and reversible manner, providing information about the packing density. Iodine- and nitrile-functionalized βCD monolayers gave coverages close to maximum packing. Electron transfer in the presence of Fe(CN) studied by impedance spectroscopy revealed that the electron transfer of the diffusing probe was 3 orders of magnitude faster than when the βCD cores were separated from the surface by undecyl chains. When an electrochemically active guest was immobilized on the surface, electron-transfer rate measurements by cyclic voltammetry and capacitance spectroscopy showed differences of up to a factor of 8 for different βCD monolayers. These results suggest that increasing the distance between the βCD core and the underlying conductive substrate leads to a diminishing of the electron-transfer rate.
我们研究了 β-环糊精（βCD）主体核心与导电基底之间的距离对复合客体以及自由扩散电化学活性探针的电子转移速率的影响。首先，我们评估了一系列具有不同锚固基团的短链βCD 吸附剂，以便为短程电子转移研究提供可靠的平台。电化学活性三价客体以选择性和可逆的方式固定在这些主体单层上，提供了关于组装密度的信息。碘和腈基功能化的βCD 单层的覆盖率接近最大组装密度。通过阻抗谱研究发现，在存在 Fe(CN)的情况下的电子转移速度比βCD 核通过十一烷基链与表面分离时快 3 个数量级。当将电化学活性客体固定在表面上时，通过循环伏安法和电容谱法进行的电子转移速率测量表明，不同的βCD 单层之间的差异高达 8 倍。这些结果表明，增加βCD 核与基底之间的距离会导致电子转移速率降低。
