Department of Chemical Engineering, National Taiwan University, Taipei 10617, Taiwan; Department of Chemical Engineering, National Taiwan University of Science and Technology, Taipei 10607, Taiwan.
Department of Chemical Engineering, National Taiwan University, Taipei 10617, Taiwan.
J Colloid Interface Sci. 2019 Mar 1;537:358-365. doi: 10.1016/j.jcis.2018.11.020. Epub 2018 Nov 10.
Extending previous electrokinetic analyses based on a Newtonian fluid to power-law fluids, we investigate the behaviors of the ion current rectification (ICR) and the ion selectivity S of a conical nanopore having a pH-regulated surface. The bulk salt concentration C, the solution pH, and the power-law index n are examined in detail for their influences on these behaviors. We show that the ICR ratio for the case where pH is lower than the isoelectric point (IEP) of the nanopore surface is different both quantitatively and qualitatively from that for the case where pH > IEP. The relative magnitude of the ICR ratio as n varies depends largely on the level of C. In contrast, S (pH < IEP) is qualitatively similar to that for S(pH > IEP), where |S| decreases with increasing C and/or decreasing n. In addition, S is very sensitive to n, for example, a decrease of n from 1.0 (Newtonian fluid) to 0.9 (pseudoplastic fluid) can yield a 245% increase in S at C = 100 mM. Implying that the performance of ion separation can be improved by tuning the fluid viscosity. Mechanisms are proposed for explaining the observed behaviors in the ICR ratio.
将先前基于牛顿流体的电流整流（ICR）和离子选择性（S）的动电分析扩展到幂律流体，我们研究了表面 pH 可调的圆锥形纳米孔中离子电流整流（ICR）和离子选择性（S）的行为。详细考察了 bulk salt concentration C、solution pH 和 power-law index n 对这些行为的影响。我们表明，pH 低于纳米孔表面等电点（IEP）的情况下的 ICR 比值在数量和质量上都与 pH > IEP 的情况不同。ICR 比值随 n 变化的相对大小在很大程度上取决于 C 的水平。相比之下，S（pH < IEP）与 S（pH > IEP）定性相似，其中|S|随 C 和/或 n 的增加而减小。此外，S 对 n 非常敏感，例如，n 从 1.0（牛顿流体）降低到 0.9（假塑性流体）在 C = 100 mM 时可以使 S 增加 245%。这意味着通过调整流体粘度可以提高离子分离的性能。提出了一些机制来解释所观察到的 ICR 比值的行为。
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