Photo-induced ultrafast active ion transport through graphene oxide membranes

Abstract

Layered graphene oxide membranes (GOM) with densely packed sub-nanometer-wide lamellar channels show exceptional ionic and molecular transport properties. Mass and charge transport in existing materials follows their concentration gradient, whereas attaining anti-gradient transport, also called active transport, remains a great challenge. Here, we demonstrate a coupled photon-electron-ion transport phenomenon through the GOM. Upon asymmetric light illumination, cations are able to move thermodynamically uphill over a broad range of concentrations, at rates much faster than that via simple diffusion. We propose, as a plausible mechanism, that light irradiation reduces the local electric potential on the GOM following a carrier diffusion mechanism. When the illumination is applied to an off-center position, an electric potential difference is built that can drive the transport of ionic species. We further develop photonic ion switches, photonic ion diodes, and photonic ion transistors as the fundamental elements for active ion sieving and artificial photosynthesis on synthetic nanofluidic circuits.

Photodriven Active Ion Transport Through a Janus Microporous Membrane

“…Notably, the ionic current does not increase linearly with an increase in the membrane area, which is probably a consequence of the local defects in large area membranes. Notably, this illumination area‐dependent ionic current is obviously distinct from the previously reported graphene oxide membrane and g‐C 3 N 4 system, in which the photoinduced ionic current decays upon increase of the illumination area because the driving force originates from the redistribution of charge carriers caused by the off‐center partial illumination. Moreover, the photodriven active ion transport in the rGO/CMP Janus membrane demonstrates a strong dependence on the hydrated radius of ions (Supporting Information, Figure S14, Table S2), which demonstrates a great potential for precise active ion sieving.…”

Electric‐Field‐Induced Ionic Sieving at Planar Graphene Oxide Heterojunctions for Miniaturized Water Desalination

“…[ 10 ] Thus, they attract broad research interest and boost various applications in water purification and desalination, chemical sensing and separation, and energy conversion and storage. [ 11–17 ] Pristine and chemically modified GOMs effectively block organic dyes and nanoparticles, [ 18 ] but fail to exclude smaller ions with hydrated diameters less than 9 Å. [ 19 ] Toward sieving of small inorganic salt ions, a number of strategies are proposed to reduce the interlayer spacing down to merely several angstrom, such as capillary compression, [ 20 ] partial reduction, [ 21 ] and cationic control.…”

Solvation‐Involved Nanoionics: New Opportunities from 2D Nanomaterial Laminar Membranes

“…Examples of this approach include chemical functionalization and thermal annealing . Additionally, the electrons inside the materials can be modulated by the means of voltage bias or light illumination so that the electrostatic interactions (e.g., Debye screening in EDL) between ions and materials could be indirectly regulated through the coupling of electrons and ions . Examples of materials with such functionality include graphene and MoS 2 , where metal‐semiconductor transition for modulation of electrons could be achieved by controlling the reduction level or phase transition .…”

“…Examples of materials with such functionality include graphene and MoS 2 , where metal‐semiconductor transition for modulation of electrons could be achieved by controlling the reduction level or phase transition . These functionalities would allow ion transport to be responsive to external stimuli, such as electrical, optical, chemical, or mechanical changes in the environment iv)The material platforms can be readily upscaled.…”