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An ion-selective layer based on self-assembled polystyrene opals is integrated with an alumina nanoporous membrane to form nanofluidic diodes.

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.

Stable layered photochromic films with visual color switching were developed by stacking spiropyran-modified montmorillonite nanosheets.

The controllable ion transport in synthetic membranes with nanofluidic channels by external stimuli has been attracting significant attention for nanofluidic diodes, biosensing, nanoreactors, and energy conversion. Here, we report a synthetic bilayer-intercalated layered membrane with two-dimensional (2D) nanofluidic channels, in which the ion transport can be controlled by external stimuli of temperature and voltage. The synthesis of the layered membranes includes the exchange of native cations in montmorillonite with the quaternary ammonium ions in a cationic surfactant and a subsequent vacuum filtration. The bilayer-intercalated interlayer spaces in the layered membranes act as 2D nanofluidic channels for ion transport. The phase state of the bilayers and the surface polarity of functionalized montmorillonite lamellae can be controlled by external temperature and voltage, respectively, which imbue the layered membranes with dual-responsive ion transport properties. Our dual-responsive layered membranes with 2D nanofluidic channels provide a new platform for creating smart synthetic membranes to control the ion transport.

The harvesting of the energy stored in the salinity gradient between seawater and river water by a membrane‐scale nanofluidic diode for sustainable generation of electricity is attracting significant attention in recent years. However, the performance of previously reported nanofluidic diodes is sensitive to the pH conditions, which restricts their potential applications in wider fields with variable pH values. Herein, a pH‐resistant membrane‐scale nanofluidic diode with a high ion rectification ratio of ≈85 that demonstrates a stable ion rectification property over a wider pH range from 4 to 10 is reported. This pH‐resistant ion rectification is explained quantitatively by a theoretical calculation based on the Poisson and Nernst–Plank equations. The nanofluidic diode membrane is integrated into a power generation device to harvest the energy stored in the salinity gradient. By mixing the simulated seawater (0.5 m KCl) and river water (0.01 m KCl) through the membrane, the device outputs an impressive power density of 3.15 W m−2 and demonstrates high stability over a wider pH range. The membrane‐scale nanofluidic diode provides a pH‐resistant platform to control the ion transport and to convert the salinity gradient into electric energy.

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