Photosynthetic‐Membrane‐Like Ion Translocation in Visible‐Light‐Harvesting Nanofluidic Channels

Abstract

The selective uphill and downhill movement of protons in and out of photosynthetic membrane enabled by ion pumps and ion channels is key to photosynthesis. Reproducing the functions of photosynthetic membranes in artificial systems has been a persistent goal. Here, a visible‐light‐harvesting nanofluidic channels is reported which experimentally demonstrates the ion translocation functions of photosynthetic membranes. A molecular junction consisting of photosensitive ruthenium complexes linked to TiO2 electron acceptors forms the reaction centers in the nanofluidic channels. The visible‐light‐triggered vectorial electron injection into TiO2 establishes a difference in transmembrane potential across the channels, which enables uphill transport of ions against a 5‐fold concentration gradient. In addition, the asymmetric charge distribution across the channels enables the unidirectional downhill movement of ions, demonstrating an ion rectification effect with a ratio of 18:1. This work, for the first time, mimics both the uphill and downhill ion translocation functions of photosynthetic membranes, which lays a foundation for nanofluidic energy conversion.

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

“…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.…”