Rectification of ion current in nanopipettes by external substrates.
Rectification of ion current in nanopipettes by external substrates.
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DOI：
10.1021/nn4050485
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发表时间：
2013-12-23
期刊：
影响因子：
17.1
通讯作者：
Baker LA
中科院分区：
文献类型：
--
作者：
Sa N;Lan WJ;Shi W;Baker LA
我们描述了离子分布和纳米吸管在不同探针-衬底距离（Dps）下的电流-电压（i-V）响应，并通过有限元方法模拟。结果表明，当Dps在德拜长度的一个数量级内（模拟中采用的1 mM溶液约为10 nm）时，带电衬底与纳米吸管之间的静电相互作用主导了电泳离子通过纳米吸管的传输。中性或带电纳米吸管的离子电流整流（ICR）和过电选择性可以可逆地增强或降低，这取决于衬底的Dps、电荷极性和电荷密度（σ）。纳米管电流的调节是纳米管内部离子富集或耗尽的结果，从而影响纳米管的电导率。当外部衬底的负电荷小于纳米吸管时，衬底的ICR先降低，然后随着Dps的降低而提高。令人惊讶的是，实验和模拟数据都表明，中性底物也能够降低和逆转微带负电荷的纳米吸管的ICR。模拟结果将这种效应归因于纳米吸管内正电位离子耗尽的消除。
We describe ion distribution and the current-voltage (i-V) response of nanopipettes at different probe-to-substrate distances (Dps) as simulated by finite-element methods. Results suggest electrostatic interactions between a charged substrate and the nanopipette dominate electrophoretic ion transport through the nanopipette when Dps is within one order of magnitude of the Debye length (~10 nm for a 1 mM solution as employed in the simulation). Ion current rectification (ICR) and permselectivity associated with a neutral or charged nanopipette can be reversibly enhanced or reduced dependent on Dps, charge polarity and charge density (σ) of the substrate. Regulation of nanopipette current is a consequence of the enrichment or depletion of ions within the nanopipette interior which influences conductivity of the nanopipette. When the external substrate is less negatively charged than the nanopipette, the substrate first reduces, and then enhances the ICR as Dps decreases. Surprisingly, both experimental and simulated data show that a neutral substrate was also able to reduce and reverse the ICR of a slightly negatively charged nanopipette. Simulated results ascribe such effects to the elimination of ion depletion within the nanopipette at positive potentials.
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