Nat. Commun. 10, 1171 (2019)

Biological systems can harvest light to regulate proton transport across cell membranes. During the past decade, artificial photo-induced active transport systems, capable of transporting protons or metal ions and mimicking natural photosynthetic process, have successfully been built. Now Yang and co-workers report a photo-induced fast ion transport phenomenon through graphene oxide membranes (GOMs).

They prepare GOMs by vacuum filtration of GO and thermal annealing. The test device is then composed of the GOMs and two solution reservoirs placed on each end. When an off-centre position is illuminated, photocurrent and ionic current flow through, without the application of an external potential. Besides, the researchers observe cation transport against a tenfold concentration gradient under asymmetric light illumination and find that both enhancing the illumination intensity and prolonging the illumination time can facilitate ion transport. However, no ionic transport is present when part of the GOM is directly heated, excluding a light induced thermal effect. The researchers propose a plausible mechanism of a photo-induced charge profile redistribution. Photonic ion switches, photonic ion diodes and photonic ion transistors are subsequently developed based on the GOMs. The authors believe that these fundamental elements can find their use in ionic sieving and artificial photosynthesis in the future.