The Effect of Tip Diameter and Electrolyte Properties on Ion 2 Transport and Current Rectification in Asymmetric Nanochannels

Abstract

In this study, the dependence of the ionic current rectification (ICR) phenomenon on the charge and concentration of the electrolyte solution in a conical nanochannel was investigated experimentally. Moreover, the dependence of current rectification on the tip radius of the nanochannel was also investigated. A thermoplastic polyurethane membrane with a conical nanochannel in the center was used in the experiments. ICR is represented as diodelike current-to-voltage curves where the current recorded for one voltage polarity is higher than the current recorded for the same absolute voltage value in the opposite polarity. Through the experiments, it is revealed that the amount of ICR that occurs in a conical nanochannel can be adjusted by three different parameters. First, it is shown that current rectification increases with increasing charge, when the concentration of the electrolyte is kept constant and its charge is changed. Thus, the amount of ICR can be increased by up to 88% through altering the charge of the electrolyte. It is also observed that the current rectification can be changed up to 7 times when the electrolyte concentration is modified. Finally, in the case where no change is made in the electrolyte but the nanochannel tip radius is increased, it is observed that the ionic current rectification can be changed up to 4.6 times. In all three cases, it is concluded that the amount of ionic current in a conical nanochannel can be controlled when proper modification is made to the electrolyte or the tip radius of the nanochannel.

Keywords

• current rectification
• electrokinetic flow
• electrical double layer
• rectification coefficient
• asymmetric nanochannel