School of Chemistry, The University of New South Wales, Sydney, NSW, 2052, Australia.
J Am Chem Soc. 2012 May 2;134(17):7539-44. doi: 10.1021/ja301509h. Epub 2012 Apr 17.
Herein, we report the first experimental investigation on the effect of varying the position of redox-active moieties, within the electrical double layer, on the apparent formal potential and on the electron transfer rate constant. This was achieved using a rigid class of molecules, norbornylogous bridges, to place redox species (ferrocene) at a fixed position above the surface of the electrode. Cyclic voltammetry and alternating current voltammetry were used to calculate the apparent formal potential and the electron transfer rate constant for the electron transfer between the ferrocene and the gold electrode. We use the effect of electric field on the apparent formal potential measurement of the surface-bound redox species to calculate the potential drop from the initiation of the electrical double layer to different distances above it. It was found that self-assembled monolayers formed from ω-hydroxyalkanethiol have a potential profile very similar to that described by classical theories for bare metal electrodes. A steep drop in potential in the Stern layer was observed followed by a smaller potential drop in the Gouy-Chapman layer. The electron transfer rate constant was found to decrease as the distance between the ferrocene moiety and the initiation of the double layer is increased. Thus, the electron transfer rate constant appears to be dependent on ion concentration.
在此，我们报告了关于在电双层内改变氧化还原活性部分位置对表观标准电势和电子转移速率常数的影响的首次实验研究。这是通过使用刚性分子类，即降冰片烷桥，将氧化还原物质（二茂铁）固定在电极表面上方的固定位置来实现的。循环伏安法和交流伏安法用于计算二茂铁和金电极之间电子转移的表观标准电势和电子转移速率常数。我们利用电场对表面结合氧化还原物质的表观标准电势测量的影响来计算从双电层开始到其上方不同距离的电势降。结果发现，由ω-羟烷硫醇自组装形成的单层具有与经典理论描述的裸金属电极非常相似的电势分布。在斯特恩层中观察到电势急剧下降，随后在古依-查普曼层中电势下降较小。随着二茂铁部分与双电层起始点之间的距离增加，电子转移速率常数减小。因此，电子转移速率常数似乎取决于离子浓度。
