Ion transport in a pH-regulated conical nanopore filled with a power-law fluid

摘要

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 Sofa conical nanopore having a pH-regulated surface. The bulk salt concentration C-bu(lk), 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-bulk. In contrast, S (pH IEP) is qualitatively similar to that for S(pH IEP), where vertical bar S vertical bar decreases with increasing C-b(ulk), 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-bulk = 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. (C) 2018 Elsevier Inc. All rights reserved.