Organic/Inorganic Hybrid Nanochannels Based on Polypyrrole-Embedded Alumina Nanopore Arrays: pH- and Light-Modulated Ion Transport

Inspired by the asymmetric structure and responsive ion transport in biological ion channels, organic/inorganic hybrid artificial nanochannels exhibiting pH-modulated ion rectification and light-regulated ion flux have been constructed by introducing conductive polymer into porous nanochannels. The hybrid nanochannels are achieved by partially modifying alumina (Al2O3) nanopore arrays with polypyrrole (PPy) layer using electrochemical polymerization, which results in an asymmetric component distribution. The protonation and deprotonation of Al2O3 and PPy upon pH variation break the surface charge continuity, which contributes to the pH-tunable ion rectification. The ionic current rectification ratio is affected substantially by the pH value of electrolyte and the pore size of nanochannels. Furthermore, the holes (positive charges) in PPy layer induced by the cooperative effect of light and protons are used to regulate the ionic flux through the nanochannels, which results in a light-responsive ion current. The magnitude of responsive ionic current could be amplified by optimizing this cooperation. This new type of stimuli-responsive PPy/Al2O3 hybrid nanochannels features advantages of unique optical and electric properties from conducting PPy and high mechanical performance from porous Al2O3 membrane, which provide a platform for creating smart nanochannels system.