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Constant-distance mode scanning potentiometry. High resolution pH measurements in three-dimensions

机译：等距模式扫描电位计。三维高分辨率pH测量

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A very small liquid-membrane based pH probe (less than 500 nm diameter) has been implemented in scanning electrochemical microscopy (SECM) equipped with a nonoptical shear force-based distance control. This constant-distance mode pH microscopy was tested over a complex microcavity (50 mu m diameter, 8 gm deep) possessing three individually-addressable gold electrodes: a microdisk at the bottom, a microcrescent ring 4 mu m away and along the wall, and a planar macroelectrode around the rim at the top. All the experiments were performed in a buffer of pH 6.22. The pH inside the microcavity was modified locally by applying negative potential (reduction of O-2 and H2O to produce OH-) either at the ring or disk electrodes. The shear force-sensitive signal permitted the precise determination of the tip-to-sample distance. Moreover, operating in constant-distance mode, the tip-to-sample distance was kept constant (less than 200 nm) while scanning the electrode over the sample. The simultaneous collection of both topographic and potentiometric information allowed a better understanding of the complex electrochemical processes occurring within the microcavity. Since potentiometry is not disturbing diffusion profiles in front of active electrodes constant-distance scanning potentiometry can be applied for the visualization of processes occurring in close proximity to electrode surfaces. This is especially important for the elucidation of properties of redox recycling systems often applied in amplified electrochemical assays.
机译：在配有基于非光学剪切力的距离控制的扫描电化学显微镜（SECM）中，已经实现了非常小的基于液膜的pH探针（直径小于500 nm）。在具有三个可单独寻址的金电极的复杂微腔（直径50μm，深8 gm）上对这种恒定距离模式的pH显微镜进行了测试：底部有一个微型圆盘，底部有一个4 mm远且沿着壁的微月形环，以及顶部边缘周围的平面大电极。所有实验均在pH 6.22的缓冲液中进行。通过在环形电极或圆盘电极上施加负电势（还原O-2和H2O以产生OH-），可局部改变微腔内的pH。剪切力敏感信号允许精确确定吸头到样品的距离。此外，在恒定距离模式下操作时，在样品上扫描电极时，针尖到样品的距离保持恒定（小于200 nm）。同时收集地形和电位信息可以更好地了解微腔内发生的复杂电化学过程。由于电位计不会干扰有源电极前的扩散曲线，因此可以将恒定距离扫描电位计用于可视化紧邻电极表面的过程。这对于阐明经常用于放大电化学分析中的氧化还原循环系统的特性尤其重要。

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