Influence of shape and charged conditions of nanopores on their ionic current rectification, electroosmotic flow, and selectivity

Abstract

The electrokinetic behaviors, including ionic current rectification (ICR), selectivity, and electroosmotic flow (EOF) of a nanopore play important role in applications such as nano sensing, salinity gradient power, and desalination of sea water. Since those behaviors can be influenced significantly by the shape and charged conditions of a nanopore, the influence of these factors on its performance is studied in detail by comparing the behavior of six types of nanopore (conical, cylindrical, cigar, funnel, hourglass, and dumbbell-shaped pores), each of them can be unipolarly or bipolarly charged. In addition to examining their performance under various conditions, the associated mechanisms are also discussed. We show that the internal volume of a nanopore is the most important factor influencing its ICR behavior. However, the selectivity of a nanopore depends both on its internal volume and the fraction of its narrow region. The bipolar and unipolar nature of a nanopore can yield interesting velocity profile, which is also influenced by the salt concentration and nanopore geometry.