The energy conversion in active transport of ions

Photo-Driven Ion Directional Transport across Artificial Ion Channels: Band Engineering of WS2 via Peptide Modification

Biological photo-responsive ion channels play important roles in the important metabolic processes of living beings. To mimic the unique functions of biological prototypes, the transition metal dichalcogenides, owing to their excellent mechanical, electrical, and optical properties, are already used for artificial intelligent channel constructions. However, there remain challenges to building artificial bio-semiconductor nanochannels with finely tuned band gaps for accurately simulating or regulating ion transport. Here, two well-designed peptides are employed for the WS2 nanosheets functionalization with the sequences of PFPFPFPFC and DFDFDFDFC (PFC and DFC; P: proline, D: aspartate, and F: phenylalanine) through cysteine (Cys, C) linker, and an asymmetric peptide-WS2 membrane (AP-WS2M) could be obtained via self-assembly of peptide-WS2 nanosheets. The AP-WS2M could realize the photo-driven anti-gradient ion transport and vis-light enhanced osmotic energy conversion by well-designed working patterns. The photo-driven ion transport mechanism stems from a built-in photovoltaic motive force with the help of formed type II band alignment between the PFC-WS2 and DFC-WS2. As a result, the ions would be driven across the channels of the membrane for different applications. The proposed system provides an effective solution for building photo-driven biomimetic 2D bio-semiconductor ion channels, which could be extensively applied in the fields of drug delivery, desalination, and energy conversion.

Bioinspired Artificial Ion Pumps

Ion pumps are important membrane-spanning transporters that pump ions against the electrochemical gradient across the cell membrane. In biological systems, ion pumping is essential to maintain intracellular osmotic pressure, to respond to external stimuli, and to regulate physiological activities by consuming adenosine triphosphate. In recent decades, artificial ion pumping systems with diverse geometric structures and functions have been developing rapidly with the progress of advanced materials and nanotechnology. In this Review, bioinspired artificial ion pumps, including four categories: asymmetric structure-driven ion pumps, pH gradient-driven ion pumps, light-driven ion pumps, and electron-driven ion pumps, are summarized. The working mechanisms, functions, and applications of those artificial ion pumping systems are discussed. Finally, a brief conclusion of underpinning challenges and outlook for future research are tentatively discussed.