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Enhanced transport of ions by tuning surface properties of the nanochannel
Physical Review E ( IF 2.2 ) Pub Date : 2021-09-22 , DOI: 10.1103/physreve.104.035107 Olga I Vinogradova 1 , Elena F Silkina 1 , Evgeny S Asmolov 1
Physical Review E ( IF 2.2 ) Pub Date : 2021-09-22 , DOI: 10.1103/physreve.104.035107 Olga I Vinogradova 1 , Elena F Silkina 1 , Evgeny S Asmolov 1
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Motivated by recent observations of anomalously large deviations of the conductivity currents in confined systems from the bulk behavior, we revisit the theory of ion transport in parallel-plate channels and also discuss how the wettability of a solid and the mobility of adsorbed surface charges impact the transport of ions. It is shown that depending on the ratio of the electrostatic disjoining pressure to the excess osmotic pressure at the walls two different regimes occur. In the thick channel regime this ratio is small and the channel effectively behaves as thick, even when the diffuse layers strongly overlap. The latter is possible for highly charged channels only. In the thin channel regime the disjoining pressure is comparable to the excess osmotic pressure at the wall, which implies relatively weakly charged walls. We derive simple expressions for the mean conductivity of the channel in these two regimes, highlighting the role of electrostatic and electrohydrodynamic boundary conditions. Our theory provides a simple explanation of the high conductivity observed experimentally in hydrophilic channels, and allows one to obtain rigorous bounds on its attainable value and scaling with salt concentration. Our results also show that further dramatic amplification of conductivity is possible if hydrophobic slip is involved, but only in the thick channel regime provided the walls are sufficiently highly charged and most of the adsorbed charges are immobile. However, for weakly charged surfaces the massive conductivity amplification due to hydrodynamic slip is impossible in both regimes. Interestingly, in this case the moderate slip-driven contribution to conductivity can monotonously decrease with the fraction of immobile adsorbed charges. These results provide a framework for tuning the conductivity of nanochannels by adjusting their surface properties and bulk electrolyte concentrations.
中文翻译：
通过调整纳米通道的表面特性增强离子传输
受最近观察到的受限系统中电导电流与本体行为的异常大偏差的启发，我们重新审视了平行板通道中的离子传输理论，并讨论了固体的润湿性和吸附表面电荷的迁移率如何影响离子的运输。结果表明，根据静电分离压力与壁处过量渗透压的比率，会出现两种不同的状态。在厚通道状态下，该比率很小，并且通道有效地表现得一样厚，即使当扩散层强烈重叠时也是如此。后者仅适用于高电荷通道。在细通道状态下，分离压力与壁处的过量渗透压相当，这意味着壁带电相对较弱。我们推导出这两种状态下通道平均电导率的简单表达式，突出了静电和电流体动力学边界条件的作用。我们的理论提供了对亲水通道中实验观察到的高电导率的简单解释，并允许人们对其可达到的值和盐浓度缩放获得严格的界限。我们的结果还表明，如果涉及疏水性滑移，则电导率的进一步显着放大是可能的，但仅在厚通道区域内，前提是壁具有足够高的电荷并且大多数吸附电荷是不动的。然而，对于弱带电表面，由于流体动力滑移而导致的大量电导率放大在两种情况下都是不可能的。有趣的是，在这种情况下，适度的滑移驱动对电导率的贡献可以随着固定吸附电荷的分数而单调减少。这些结果为通过调整纳米通道的表面性质和本体电解质浓度来调节纳米通道的电导率提供了框架。
更新日期：2021-09-22
中文翻译：
通过调整纳米通道的表面特性增强离子传输
受最近观察到的受限系统中电导电流与本体行为的异常大偏差的启发，我们重新审视了平行板通道中的离子传输理论，并讨论了固体的润湿性和吸附表面电荷的迁移率如何影响离子的运输。结果表明，根据静电分离压力与壁处过量渗透压的比率，会出现两种不同的状态。在厚通道状态下，该比率很小，并且通道有效地表现得一样厚，即使当扩散层强烈重叠时也是如此。后者仅适用于高电荷通道。在细通道状态下，分离压力与壁处的过量渗透压相当，这意味着壁带电相对较弱。我们推导出这两种状态下通道平均电导率的简单表达式，突出了静电和电流体动力学边界条件的作用。我们的理论提供了对亲水通道中实验观察到的高电导率的简单解释，并允许人们对其可达到的值和盐浓度缩放获得严格的界限。我们的结果还表明，如果涉及疏水性滑移，则电导率的进一步显着放大是可能的，但仅在厚通道区域内，前提是壁具有足够高的电荷并且大多数吸附电荷是不动的。然而，对于弱带电表面，由于流体动力滑移而导致的大量电导率放大在两种情况下都是不可能的。有趣的是，在这种情况下，适度的滑移驱动对电导率的贡献可以随着固定吸附电荷的分数而单调减少。这些结果为通过调整纳米通道的表面性质和本体电解质浓度来调节纳米通道的电导率提供了框架。
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