Brooksby Paula A, Downard Alison J, Yu Samuel S C
MacDiarmid Institute for Advanced Materials and Nanotechnology, Department of Chemistry, University of Canterbury, Private Bag 4800, Christchurch, New Zealand.
Langmuir. 2005 Nov 22;21(24):11304-11. doi: 10.1021/la051964c.
Arylmethyl films have been grafted to glassy carbon surfaces and to pyrolyzed photoresist films (PPFs) by electrochemical oxidation of 1-naphthylmethylcarboxylate and 4-methoxybenzylcarboxylate. Atomic force microscopy (AFM) and electrochemistry were used to characterize the as-prepared films and to monitor changes induced by post-preparation treatments. Film thickness was measured by depth profiling using an AFM tip to remove film from the PPF surface. Surface coverage of electroactive modifiers was estimated from cyclic voltammetry, and monitoring the response of a solution-based redox probe at grafted surfaces gave a qualitative indication of changes in film properties. For preparation of the films, the maximum film thickness increased with the potential applied during grafting, and all films were of multilayer thickness. The apparent rate of electron transfer for the Fe(CN)(6)3-/Fe(CN)(6)4- couple was very low at as-prepared films. After film-grafted electrodes were transferred to pure acetonitrile-electrolyte solution and subjected to negative potential excursions, the response of the Fe(CN)(6)3-/Fe(CN)(6)4- couple changed and was consistent with faster electron-transfer kinetics, the film thickness decreased and the surface roughness increased substantially. Applying a positive potential to the treated film reversed changes in film thickness, but the voltammetric response of the Fe(CN)(6)3-/Fe(CN)(6)4- couple remained kinetically fast. After as-prepared films were subjected to positive applied potentials in acetonitrile-electrolyte solution, the apparent rate of electron transfer for the Fe(CN)(6)3-/Fe(CN)(6)4- couple remained very slow and the measured film thickness was the same or greater than that before treatment at positive potentials. Mechanisms are considered to explain the observed effects of applied potential on film characteristics.
通过对1-萘基甲基羧酸酯和4-甲氧基苄基羧酸酯进行电化学氧化，芳基甲基薄膜已接枝到玻碳表面和热解光刻胶薄膜（PPF）上。使用原子力显微镜（AFM）和电化学方法对制备好的薄膜进行表征，并监测制备后处理所引起的变化。通过使用AFM针尖从PPF表面去除薄膜进行深度剖析来测量薄膜厚度。根据循环伏安法估算电活性修饰剂的表面覆盖率，并且监测基于溶液的氧化还原探针在接枝表面的响应可以定性指示薄膜性质的变化。对于薄膜的制备，最大薄膜厚度随着接枝过程中施加的电位增加而增加，并且所有薄膜均为多层厚度。在制备好的薄膜上，Fe(CN)(6)3-/Fe(CN)(6)4-电对的表观电子转移速率非常低。将薄膜接枝电极转移到纯乙腈电解质溶液中并进行负电位偏移后，Fe(CN)(6)3-/Fe(CN)(6)4-电对的响应发生变化，并且与更快的电子转移动力学一致，薄膜厚度减小且表面粗糙度大幅增加。对处理后的薄膜施加正电位可逆转薄膜厚度的变化，但Fe(CN)(6)3-/Fe(CN)(6)4-电对的伏安响应在动力学上仍然很快。在制备好的薄膜在乙腈电解质溶液中施加正电位后，Fe(CN)(6)3-/Fe(CN)(6)4-电对的表观电子转移速率仍然非常慢，并且测得的薄膜厚度与在正电位处理之前相同或更大。文中考虑了相关机制来解释所观察到的施加电位对薄膜特性的影响。
