Department of Chemistry, Aarhus University, Langelandsgade 140, DK-8000 Aarhus C, Denmark.
Langmuir. 2013 Apr 30;29(17):5181-9. doi: 10.1021/la305081c. Epub 2013 Apr 15.
The mechanism of electrogenerated acid-facilitated electrografting (EGAFE) of the aryltriazene, 4-(3,3-dimethyltriaz-1-enyl)benzyl-1-ferrocene carboxylate, was studied in detail using electrochemical quartz crystal microbalance (EQCM) and cyclic voltammetry. The measurements support the previously suggested mechanism that electrochemical oxidation of the EGA agent (i.e., N,N'-diphenylhydrazine) occurs on the forward oxidative sweep to generate protons, which in turn protonate the aryltriazene to form the corresponding aryldiazonium salt close to the electrode surface. On the reverse sweep, the electrochemical reduction of the aryldiazonium salt takes place, resulting in the electrografting of aryl groups. The EGAFE-generated film consists of a densely packed layer of ferrocenyl groups with nearly ideal electrochemical properties. The uncharged grafted film contains no solvent and electrolyte, but counterions and solvent can easily enter and be accommodated in the film upon charging. It is shown that all ferrocene moieties present in the multilayered film are electrochemically active, suggesting that the carbon skeleton possesses a sufficiently high flexibility to allow the occurrence of fast electron transfers between the randomly located redox stations. In comparison, EQCM measurements on aryldiazonium-grafted films reveal that they have a substantially smaller electrolyte uptake during charging and that they contain only 50% electroactive ferrocenyl groups relative to weight. Hence, half of these films consist of entrapped supporting electrolyte/solvent and/or simply electrochemically inactive material due to solvent inaccessibility.
用电化学石英晶体微天平（EQCM）和循环伏安法详细研究了芳基三氮烯，4-（3,3-二甲基三氮烯-1-基）苄基-1-二茂铁羧酸酯的电生成酸促进的电化学接枝（EGAFE）的机理。这些测量结果支持了先前提出的机理，即在正向氧化扫掠过程中，EGA 试剂（即 N,N'-二苯基肼）发生电化学氧化生成质子，质子进而将芳基三氮烯质子化形成靠近电极表面的相应芳基重氮盐。在反向扫描时，芳基重氮盐发生电化学还原，导致芳基的电化学接枝。EGAFE 生成的膜由几乎理想的电化学性质的紧密堆积的二茂铁基团层组成。不带电的接枝膜不含溶剂和电解质，但在充电时，抗衡离子和溶剂可以很容易地进入并容纳在膜中。结果表明，多层膜中存在的所有二茂铁部分均具有电化学活性，这表明碳骨架具有足够的柔韧性，允许在随机定位的氧化还原站之间快速进行电子转移。相比之下，芳基重氮接枝膜的 EQCM 测量表明，在充电过程中它们的电解质吸收量要小得多，并且相对于重量，它们仅包含 50％的电化学活性二茂铁基团。因此，这些膜的一半由于溶剂不可及性而包含有嵌入的支持电解质/溶剂和/或简单的电化学惰性材料。
