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

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. Visible-light-harvesting nanofluidic channels consisting of cis-bis(isothiocyanato)bis(2,2 '-bipyridyl-4,4 '-dicarboxylato) ruthenium (II) sensitized TiO2 nanoparticles on an Al2O3 porous membrane demonstrates the ion translocation functions of photosynthetic membranes. The visible-light-induced potential difference and the asymmetric charge distribution across the channels enables the uphill and downhill movement of ions respectively. image