Department of Chemistry, Aarhus University, Langelandsgade 140, DK-8000 Aarhus, Denmark.
Langmuir. 2012 Jun 26;28(25):9573-82. doi: 10.1021/la301391s. Epub 2012 Jun 11.
Redox grafting of aryldiazonium salts containing redox units may be used to form exceptionally thick covalently attached conducting films, even in the micrometers range, in a controlled manner on glassy carbon and gold substrates. With the objective to investigate the mechanism of this process in detail, 1-anthraquinone (AQ) redox units were immobilized on these substrates by electroreduction of 9,10-dioxo-9,10-dihydroanthracene-1-diazonium tetrafluoroborate. Electrochemical quartz crystal microbalance was employed to follow the grafting process during a cyclic voltammetric sweep by recording the frequency change. The redox grafting is shown to have two mass gain regions/phases: an irreversible one due to the addition of AQ units to the substrate/film and a reversible one due to the association of cations from the supporting electrolyte with the AQ radical anions formed during the sweeping process. Scanning electrochemical microscopy was used to study the relationship between the conductivity of the film and the charging level of the AQ redox units in the grafted film. For that purpose, approach curves were recorded at a platinum ultramicroelectrode for AQ-containing films on gold and glassy carbon surfaces using the ferro/ferricyanide redox system as redox probe. It is concluded that the film growth has its origin in electron transfer processes occurring through the layer mediated by the redox moieties embedded in the organic film.
通过将含有氧化还原单元的芳基重氮盐进行氧化还原接枝，可以在玻璃碳和金基底上以可控的方式形成异常厚的共价附着的导电膜，甚至在微米范围内也是如此。为了详细研究这个过程的机制，通过电化学还原 9,10-二氧代-9,10-二氢蒽-1-重氮四氟硼酸盐，将 1-蒽醌（AQ）氧化还原单元固定在这些基底上。电化学石英晶体微天平（EQCM）通过记录频率变化，在循环伏安扫描过程中用于跟踪接枝过程。氧化还原接枝有两个质量增益区域/阶段：一个是不可逆的，由于 AQ 单元添加到基底/膜中，另一个是可逆的，由于支持电解质中的阳离子与在扫描过程中形成的 AQ 自由基阴离子缔合。扫描电化学显微镜（SECM）用于研究接枝膜中膜的电导率与 AQ 氧化还原单元的充电水平之间的关系。为此，使用亚铁/铁氰化物氧化还原探针，在金和玻璃碳表面上的含 AQ 膜上记录了白金超微电极的接近曲线。结论是，膜生长起源于通过嵌入有机膜中的氧化还原部分介导的层中的电子转移过程。
