3,3′,5,5′-四甲基联苯胺在铂网栅光透电极上的薄层光谱电化学

A Thin-layer Spectroelectrochemical Study of 3,3′,5,5′-Tetramethylbenzidine at Optically Transparent Pt Minigrid Electrode

采用薄层循环伏安法、薄层恒电位电解吸收光谱法、薄层单电位阶跃计时吸收法、薄层双电位阶跃计时吸收法等技术对3, 3′, 5, 5′-四甲基联苯胺(TMB)在B R缓冲溶液中于铂网栅光透电极上的电氧化性质进行了研究。TMB在pH=2 .0至pH<4 .0的B R缓冲溶液中为1步2电子电氧化过程,生成产物醌二亚胺,循环伏安图上表现为1对良好的氧化还原峰;在pH=4 0至pH<7. 0时为分步的2个单电子氧化过程,TMB首先被氧化为中间产物TMB自由基,然后自由基再被氧化为醌二亚胺,在循环伏安图上出现2对氧化还原峰;在pH>7 .0时为1步电氧化过程,产物为偶氮化合物,循环伏安图上为1对良好的氧化还原峰。测得了TMB的克式量电位E0′,电子转移数n。

The electrooxidation of 3,3′,5,5′-tetramethylbenzidine(TMB) was investigated at a platinum minigrid electrode by means of UV-Vis optically transparent thin-layer electrochemistry technique. In the (B-R) buffer solution, TMB (underwent) a one-step two-electron electrooxidation in the pH range from 2.0 to <4.0 with a product quinonediimine, and two successive one-electron electrooxidation processes in the pH range from 4.0 to <7.0, to yield a mediate product TMB-free radical first, and then the complete oxidative product quinonediimine. At pH 8.4, the electrooxidation of TMB was also a quasi-reversible two-electron-transfer process to yield an azo compound. Several spectroelectrochemical techniques, such as thin-layer cyclic voltammetry, thin-layer cyclic voltabsorptometry, thin-layer potential-controlled electrolysis absorptometry, thin-layer single-potential-step chronoabsorptometry, and thin-layer double-potential-step chronoabsorptometry were (applied) to this investigation. The formal potential E^(0′) and the electron transfer number corresponding to the electrooxidation of TMB in the B-R buffer solution at different pH values were determined.