Cation‐Selective Oxide Semiconductor Mesoporous Membranes for Biomimetic Ion Rectification and Light‐Powered Ion Pumping

Abstract

Artificial membranes precisely imitating the biological functions of ion channels and ion pumps have attracted significant attention to explore nanofluidic energy conversion. Herein, inspired by the cyclic ion transport for the photosynthesis in purple bacteria, a bilayer inorganic membrane (TiO2/AAO) composed of oxide semiconductor (TiO2) mesopores on anodic alumina (AAO) macropores is we developed. This inorganic membrane achieves the functions of ion channels and ion pumps, including the ion rectification and light‐powered ion pumping. The asymmetric charge distribution across the bilayer membrane contributes to the cationic selectivity and ion rectification characteristics. The electrons induced by ultraviolet irradiation introduce a built‐in electric field across TiO2/AAO membrane, which pumps the active ion transport from a low to a high concentration. This work integrates the functions of biological ion channels and ion pumps within an artificial membrane for the first time, which paves the way to explore multifunctional membranes analogous to its biological counterpart.

Semiconductor p–n Junction Nanofluidic Channels for Light-driven Ion Transport

“…Two Ag/AgCl electrodes inserted within black Teflon tubes were used to collect the ion current (Figure S5). 60 The AAO side was defined as the cathode. The ion current fluctuations at a constant voltage were measured in situ when the incident light (300 mW/cm 2 ) was alternately switched on and off.…”

“…Note that the parameters of the simplified nanochannel model for calculations of ion current were not the real values of TiO 2 /PPy/AAO membranes due to the limitation of calculation ability. The values of ion current through nanochannels with different surface positive charge density were theoretically calculated employing the “Electrostatics” and “Transport of Diluted Species” modules within COMSOL Multiphysics version 5.6. ,,, Subsequently, the light-enhanced surface charge density in PPy/AAO and TiO 2 /PPy/AAO membranes was calculated based on the experimentally measured light-enhanced percentage of ion current.…”

“…The values of ion current through nanochannels with different surface positive charge density were theoretically calculated employing the "Electrostatics" and "Transport of Diluted Species" modules within COMSOL Multiphysics version 5.6. 26,39,60,62 Subsequently, the lightenhanced surface charge density in PPy/AAO and TiO 2 /PPy/AAO membranes was calculated based on the experimentally measured light-enhanced percentage of ion current.…”

Nanoporous anodic alumina-based iontronics: fundamentals and applications

“…This system achieved an ionic rectification behavior with an efficiency of 6.26. 133 The hybrid through-hole membrane of Nafion and conical anodic alumina nanopores designed by Jung et al combined multiple asymmetries in terms of geometric, chemical, and electrostatic features. It demonstrated a rectified ion transport with the highest ICR ratio of 21.1 attained by the strong heterojunction effect of ion depletion and enrichment at positive and negative biases, respectively, at the Nafion-alumina interface.…”

Heat and osmosis cooperatively driven power generation in robust two-dimensional hybrid nanofluidic channels

“…4,5 In recent years, membrane systems with nanouidic channels were applied to achieve selective ion diffusion across the nanochannels, which provided a platform for the energy conversion from salinity or temperature gradients into electric power. [6][7][8][9][10][11][12][13][14][15][16] In nanochannel-based power generators, the conversion performance is generally evaluated by using the output power density, which is affected by the ion selectivity and ion permeability of the nanochannel membranes. [17][18][19][20][21][22] Recently, two-dimensional (2D) nanochannels have emerged as potential membrane materials for energy conversion.…”