Influence of Asymmetric Geometry on the Ion Transport of Tandem Nanochannels

Abstract

The unique ion transport properties of ion selectivity, ion current rectification, and concentration polarization at nanoscale have been extensively studied in a single nanochannel. The knowledge of ion transport in tandem nanochannels is still elusive. Here, we report an approach to construct asymmetric tandem nanochannels on an anodic aluminum oxide membrane by repeating anodization and chemical dissolution processes. Study of the ion transport of the asymmetric tandem nanochannels reveals that the tandem structure of the nanochannels significantly affects the ion distribution, which further induces different conductance profiles in the nanochannel at open and close states. It is demonstrated that the differences in the total resistance of the nanochannel between open and close states result in a gradual growth in the ion current rectification ratio of asymmetric tandem nanochannels when increasing the tandem number.

Janus Metal–Organic Framework Membranes Boosting the Osmotic Energy Harvesting

“…The I – V curves of the J-MOF membrane exhibit an obvious ion current rectification (ICR) behavior in a 100 mM KCl solution (Figure e), which can be ascribed to the asymmetric pore size (0.34 nm for ZIF-8 and 0.60 nm for UiO-66-(COOH) 2 ) and asymmetric surface charge distribution of the membrane. , The positively and negatively charged nanopores in ZIF-8 and UiO-66-(COOH) 2 layers enable the preferential transport of anions (Cl – ) and cations (K + ), respectively. As shown in Figure f, when positive voltages are applied, K + and Cl – ions can easily enter the membrane, resulting in ion accumulation and a large ion current; however, for negative voltages, K + and Cl – ions are driven out of the membrane, resulting in ion depletion and a small ion current.…”

Nanoporous anodic alumina-based iontronics: fundamentals and applications

“…The rectification effect can be measured electrically as current density–potential ( J – V ) or current–potential ( I – V ) profiles. 119 This ICR characteristic follows a non-linear diode-like behavior, with mobile ion enrichment at one potential polarity and depletion of mobile ion charge carriers at the opposite polarity. 120 Therefore, a greater ionic current is observed at one polarity than at the opposite polarity as the ionic current flow is higher in the direction of ion accumulation (Fig.…”

Pushing the limits of nanopore transport performance by polymer functionalization

“…One detrimental step towards symmetry breaking has been the directed ion transport in conically or in general asymmetrically shaped nanopores. [178][179][180][181][182] Transport direction even with homogeneous functionalization along the pore thereby results from the geometrically induced asymmetric electrostatic potential distribution along the nanopore. 162 In addition to the geometric asymmetry, functionalization has been asymmetrically designed.…”