Ionic Current Rectification in Conical Nanopores: Effect of Polyelectrolyte Modification and Nanopore Shape
Date Issued
2016
Date
2016
Author(s)
Wu, Hou-Hsueh
Abstract
Due to their specific geometry, conical nanopores are capable of yielding several interesting electrokinetic phenomena, such as ion concentration polarization (ICP) and ion current rectification (ICR). Extending previous analyses, we consider two types of nanopore: only the inner surface of a nanopore is functionalized by a polyelectrolyte (PE) layer in type I nanopore, and both its outer and inner surfaces are functionalized in type II nanopore. Numerical simulation is conducted to examine the influences of the double layer thickness and the thickness of the PE layer of a nanopore on its ICR behavior. We show that the ICP in type I nanopore is more significant than that in type II nanopore. In addition, as the bulk salt concentration varies, the rectification factors ( ) for type I and II nanopore are different significantly. In particular, if the salt concentration is low, an inversion in is observed in type I nanopore. Furthermore, we consider the case where the nanopore surface has both acidic and basic functional groups, and is pH-regulated. The influences of the nanopore shape, solution pH, and bulk salt concentration on the associated ICR behavior are examined. If the solution pH exceeds the isoelectric point, the rectification factor shows a local maximum as the curvature of the nanopore surface varies. In contrast, if it is lower than the isoelectric point, that factor increases monotonically with increasing surface curvature.
Subjects
conical nanopore
ion concentration polarization
ion current rectification
polyelectrolyte layer
electric double layer
bullet-shaped nanopore
Type
thesis
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