Light‐Powered Ion Pumping in a Cation‐Selective Conducting Polymer Membrane

Abstract

The simulation of the ion pumping against a proton gradient energized by light in photosynthesis is of significant importance for the energy conversion in a non‐biological environment. Herein, we report light‐powered ion pumping in a polystyrene sulfonate anion (PSS) doped polypyrrole (PPy) conducting polymer membrane (PSS‐PPy) with a symmetric geometry. This PSS‐PPy conducting polymer membrane exhibits a cationic selectivity and a light‐responsive surface‐charge‐governed ion transport attributed to the negatively charged PSS groups. An asymmetric visible irradiation on one side of the PSS‐PPy membrane induces a built‐in electric field across the membrane due to the intrinsic photoelectronic property of PPy, which drives the cationic transport against the concentration gradient, demonstrating an ion‐pumping effect. This work is a prototype that uses a geometry‐symmetric conducting polymer membrane as a light‐powered artificial ion pump for active ion transport, which exhibits potential applications in nanofluidic energy conversion.

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

“…Theoretical Calculation: The ion transport properties were quantitatively investigated using "Electrostatics" and "Transport of Diluted Species" modules in COMSOL Multiphysics 5.6. [33,38] To simplify the calculation, the TiO 2 /AAO membrane was theoretically modeled as a double-layer cylindrical nanochannel with a length of 600 nm, in which the segment of TiO 2 layer had a pore width of 4 nm (d 1 ) and a length of 200 nm (L 1 ), and the segment of AAO had a pore width of 17 nm (d 2 ) and a length of 400 nm (L 2 ) (Figure S7, Supporting Information). The surface charge density of TiO 2 (σ 1 ) and AAO (σ 2 ) was set to be −0.003 C m −2 and +0.002 C m −2 , respectively.…”

“…Generally, either the unidirectional or light-powered antigradient ion transport mimicking that in purple bacteria can be achieved in artificial membranes by introducing asymmetric factors. [18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33] For example, to obtain the unidirectional ion transport (i.e. ion rectification), membranes composed of polymers, [34][35][36][37][38] metal oxides, [39][40][41][42][43] nanoporous carbon, [44][45][46] or metal-organic frameworks [47,48] with asymmetric pore size, chemical composition, or charge polarity have been developed as artificial ion channels.…”

“…ion pumping), a lipid bilayer or a single-pore polymeric membrane with an asymmetrical assembly of photoactive molecules have been created to pump the cationic transport against a concentration gradient driven by light-induced charge transfer. [26][27][28] Additionally, Janus membranes with asymmetric light-sensitive materials [29,30] or being irradiated from one side of the membrane [31][32][33] also realized the light-powered ion pumping, which are attributed to the light-induced charge separation. However, the present Artificial membranes precisely imitating the biological functions of ion channels and ion pumps have attracted significant attention to explore nanofluidic energy conversion.…”

“…The UV monochromatic light (365 nm) with an intensity of 10 mW cm −2 was irradiated on the side of TiO 2 mesoporous layer. [33,80,81] The AgCl electrodes were shielded from light by inserting them into black Teflon tubes. [29] The ion current of these shielded AgCl electrodes did not show a periodic change following the light on/off when no membrane was mounted (Figure S8, Supporting Information).…”

Light‐Controlled Ionic/Molecular Transport through Solid‐State Nanopores and Nanochannels

“…In the last few years, with the rapid development of smart photo-responsive materials, such as GO and MXene, new advances are directed into the field of nanofluidic systems and, as a result, sparking the explorations of bioinspired smart devices with functions of "uphill" transport. [140,[161][162][163] Antonietti's group developed many facile methods to synthesis graphitic carbon nitride materials with abundant micro-/nano-structures and morphologies. [84] The carbon nitride materials possess [121] (B) Ionic gating property based on the interactions between GO and AZO-DNA modified PAA membrane.…”