Ionic Transport and Sieving Properties of Sub-nanoporous Polymer Membranes with Tunable Channel Size

Abstract

Bioinspired nanoporous membranes show great potential in ionic separation and water filtration by offering high selectivity with less permeation resistance. However, complex processes always limit their applications. Here, we report a convenient approach to introduce ionic selective channels in a micron-thick polycarbonate membrane through swift heavy ion irradiation accompanied by UV sensitization and pulsed-electrical etching. The characteristic dimension of channels was tuned through regulating energy loss of the incident ion and UV sensitization time of the membrane, resulting in the subnanoporous membranes with mean channel diameter ranging from <2.4 to 9.7 Å. These membranes showed the voltage-activated ionic transport properties associated with the dehydration effect, and the corresponding I−V characteristics were related to ionic strength, solution pH, ionic type, and channel diameter. It was found that the transmembrane conduction of multivalent ions was severely suppressed compared to monovalent ions, until the size of the membrane channel was comparable to the hydrated diameter of multivalent ions. Ionic sieving experiments also demonstrated the excellent ionic valence selectivity of the membrane. Even for the membrane with a channel diameter close to 1 nm, the Li + /Mg 2+ separation ratio was still as high as 40, and an even higher separation ratio was found for Li + /La 3+ (>3000).

Enhanced Ion Rejection in Carbon Nanotubes by a Lateral Electric Field

“…6,7 State-of-the-art membranes with specific structures or novel materials bring hope for breaking this trade-off and achieving efficient seawater desalination. 2,8,9 Particularly, some carbon-based membranes, including nanopores composed of graphene monolayers and smooth-walled carbons with a smooth surface and a controllable atomic-scale pore size, exhibit a high water permeability and satisfactory salt rejection. 10−13 Most recently, the fast water transport in carbon nanochannels has been successfully explained by a quantum theory of the solid−liquid interface, in which the coupling of charge fluctuations in the liquid to electronic excitations in the solid results in ultralow friction.…”

Sumanene Monolayer of Pure Carbon: A Two‐Dimensional Kagome‐Analogy Lattice with Desirable Band Gap, Ultrahigh Carrier Mobility, and Strong Exciton Binding Energy

“…Upon relaxation, the lattice parameters of the sumanene monolayer are 13.81 Å (α) and 13.16 Å (β), respectively. Furthermore, we observe that the sumanene monolayer exhibits a distinct pore configuration, which may have great potential in ion‐selective transport and gas adsorption, [ 51,52 ] and we will focus on this issue in the future work. The computed phonon dispersions (Figure S2, Supporting Information) indicate that both α and β phases of sumanene monolayers are dynamically stable without any imaginary mode.…”

Bipolar Nanochannels: A Systematic Approach to Asymmetric Problems

“…Over the last decade, ion-selective materials (silicon nanochannels and nanopores, , graphene oxide-based membranes, colloid-based membranes, carbon nanotubes, − Ti 3 C 2 MXene membranes, cellulose nanofiber membrane from wood, MoS 2 nanopores, and more − ) have attracted considerable interest due to their wide variety of applications in various fields, including desalination, , energy harvesting, ,,− biomolecule sensing, and more. Particularly interesting is the potential of these materials to act as fluid-based electrical diodes where they can rectify the electric current by orders of magnitude. ,− The diodelike behavior depends on the geometry and the distribution of the surface charge density.…”