Surface charge mapping with a nanopipette.
Surface charge mapping with a nanopipette.
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DOI：
10.1021/ja506139u
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发表时间：
2014-09
影响因子：
15
通讯作者：
Kim McKelvey;S. Kinnear;David Perry;Dmitry Momotenko;P. Unwin
中科院分区：
文献类型：
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作者：
Kim McKelvey;S. Kinnear;David Perry;Dmitry Momotenko;P. Unwin
纳米移液器正在成为在纳米尺度上探测化学的简单但强大的工具。在这篇文章中，使用扫描离子电导显微镜 (SICM) 格式演示了使用纳米移液器同时进行表面电荷测绘和形貌成像。当纳米移液器靠近电解质溶液中的表面放置时，由纳米移液器中的准参比反电极（QRCE）和本体溶液中的第二个QRCE之间施加的偏压驱动的直流离子电流（DC）对表面电荷敏感。电荷敏感性的产生是因为纳米移液器和表面处的扩散双层相互作用，产生了选择性渗透区域，该区域在低离子强度（本文中为 10 mM 1:1 水性电解质）下变得越来越重要。当偏压变化时，这会导致极性相关的离子电流和表面感应整流。使用距离调制 SICM，通过周期性调制纳米移液器与表面之间的距离来感应交变离子电流分量 (AC)，探索并合理化表面电荷对 DC 和 AC 的影响。特别强调了表面电荷对交流相位（相对于驱动正弦信号）的影响；该量显示出对界面电荷高度敏感的变化，并为同时观察电荷和形貌提供了基础。本文的研究重点介绍了纳米移液器在功能成像中的应用，包括从细胞生物学到材料表征的应用，其中了解表面电荷至关重要。它们还为 SICM 实验的设计提供了一个框架，该实验可能会因地形和表面电荷效应而变得复杂，特别是对于小型纳米移液器。
Nanopipettes are emerging as simple but powerful tools for probing chemistry at the nanoscale. In this contribution the use of nanopipettes for simultaneous surface charge mapping and topographical imaging is demonstrated, using a scanning ion conductance microscopy (SICM) format. When a nanopipette is positioned close to a surface in electrolyte solution, the direct ion current (DC), driven by an applied bias between a quasi-reference counter electrode (QRCE) in the nanopipette and a second QRCE in the bulk solution, is sensitive to surface charge. The charge sensitivity arises because the diffuse double layers at the nanopipette and the surface interact, creating a perm-selective region which becomes increasingly significant at low ionic strengths (10 mM 1:1 aqueous electrolyte herein). This leads to a polarity-dependent ion current and surface-induced rectification as the bias is varied. Using distance-modulated SICM, which induces an alternating ion current component (AC) by periodically modulating the distance between the nanopipette and the surface, the effect of surface charge on the DC and AC is explored and rationalized. The impact of surface charge on the AC phase (with respect to the driving sinusoidal signal) is highlighted in particular; this quantity shows a shift that is highly sensitive to interfacial charge and provides the basis for visualizing charge simultaneously with topography. The studies herein highlight the use of nanopipettes for functional imaging with applications from cell biology to materials characterization where understanding surface charge is of key importance. They also provide a framework for the design of SICM experiments, which may be convoluted by topographical and surface charge effects, especially for small nanopipettes.