Directional and on-demand ion transport regulated by pH and voltage in submicrochannel heteromembrane based on conducting polymer

Abstract

The construction of porous ion channels with ion current rectification (ICR) at the submicron scale has great significance for the development of large-area bionic ion channel devices. In this manuscript, one kind of heterogeneous membrane with asymmetric composition, geometry and wettability was prepared by simple drop-coating of the neutral hydrophobic conducting polymer precursor and in-situ thermal polymerization on cylindrical submicron scale anodic aluminum oxide channels (D≈269 nm) at 150 °C. ICR in the submicrochannel heterogeneous membrane was successfully achieved due to the asymmetric charge distribution induced by asymmetric pH gradient. Furthermore, the rectification ratio (Ric: 1.6 ∼ 42.8) could be effectively regulated by multiple drop-coating, the electrolyte concentration (0.01 mM ∼ 1 M) and pH gradient (3 ∼ 11). Finally, through the permeation experiment of anionic dye and cationic dye, the mechanism of the synergistic effect of surface charge and electrophoresis on the ion selectivity and ICR was discussed, and it was successfully applied to the directional and on-demand transport of anionic and cationic ions under the regulation of pH gradient and voltage driving. It has important potential applications in the treatment of pollutants, the purification of water and energy conversion etc.