DIFFUSIONAL ELECTROTITRATION - GENERATION OF PH GRADIENTS OVER ARRAYS OF ULTRAMICROELECTRODES DETECTED BY FLUORESCENCE
DIFFUSIONAL ELECTROTITRATION - GENERATION OF PH GRADIENTS OVER ARRAYS OF ULTRAMICROELECTRODES DETECTED BY FLUORESCENCE
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DOI：
10.1021/ac00101a006
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发表时间：
1995-03-01
影响因子：
7.4
通讯作者：
FUHR, G
中科院分区：
文献类型：
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作者：
FIEDLER, S;HAGEDOM, R;FUHR, G
通过荧光显微镜观察电解质水溶液中平面铂和金超微电极表面附近的电极反应。直流电（0.5-5 V 直流）的毫秒脉冲导致电极附近和电极间间隙的 pH 值发生变化。这些变化导致荧光素或其葡聚糖缀合物 (MW 2 x 10(6)) 的荧光强度存在差异，从而允许可视化。电极上的氧化还原反应产生微米和亚微米尺度的 pH 梯度模式。通过添加高达 30%（w/v）的聚（乙烯基吡咯烷酮）（MW 7.5 x 10(5)），可以延迟电生成的“质子化云”的扩散耗散。我们使用 50、20、10 和 3 μm 宽的电极带，采用直流、脉冲直流或直流位移交流 (kHz-MHz) 激励。陡峭的 pH 梯度可以垂直于电极条阵列移动。可以产生速度约为 1 毫米/秒的 pH 行波。我们开发了一种数值程序来模拟电活性物质的时间依赖性浓度。数值 pH 模式与实验获得的值非常一致。电滴定及其数值模拟开辟了新的视角。微电极和超微电极应该在分析化学和生物医学研究中得到应用。微室内的滴定技术现在可能是可行的。阴极驱动电极的可视化对于评估微电极阵列的工作状态也很有用。
Electrode reactions near the surface of planar platinum and gold ultramicroelectrodes in aqueous electrolyte solutions were visualized by fluorescence microscopy. Millisecond pulses of direct current (0.5-5 V dc) caused pH alterations in the vicinity of the electrodes and in the interelectrode gaps. These changes caused differences in the fluorescence intensity of fluorescein or of its dextran conjugate (MW 2 x 10(6)), allowing visualization. Redox reactions at the electrodes created pH gradient patterns on a micrometer and submicrometer scale. It is possible to delay the diffusional dissipation of the electrogenerated ''protonation clouds'' by adding up to 30% (w/v) poly-(vinylpyrrolidone) (MW 7.5 x 10(5)). We used 50, 20, 10, and 3 mu m wide electrode strips with either dc, pulsed dc, or dc-shifted ac (kHz-MHz) excitation. Steep pH gradients could be moved perpendicular to the electrode strip array. Traveling pH waves with speeds of about similar to 1 mm/s could be generated. We have developed a numerical procedure for modeling the time-dependent concentration of electroactive species. The numerical pH patterns are in good agreement with the experimentally obtained ones. Electrotitration and its numerical modeling open new perspectives. Micro- and ultramicroelectrodes should find applications in analytical chemistry and biomedical research. Titration techniques within microcompartments may now be practicable. The visualization of cathodically driven electrodes is also useful for assessing the working state of microelectrode arrays.