title: Tunable sieving of ions using graphene oxide membranes.
abstract: Graphene oxide membranes show exceptional molecular permeation properties, with promise for many applications. However, their use in ion sieving and desalination technologies is limited by a permeation cutoff of ∼9 Å (ref. 4), which is larger than the diameters of hydrated ions of common salts. The cutoff is determined by the interlayer spacing (d) of ∼13.5 Å, typical for graphene oxide laminates that swell in water. Achieving smaller d for the laminates immersed in water has proved to be a challenge. Here, we describe how to control d by physical confinement and achieve accurate and tunable ion sieving. Membranes with d from ∼9.8 Å to 6.4 Å are demonstrated, providing a sieve size smaller than the diameters of hydrated ions. In this regime, ion permeation is found to be thermally activated with energy barriers of ∼10-100 kJ mol-1depending on d. Importantly, permeation rates decrease exponentially with decreasing sieve size but water transport is weakly affected (by a factor of <2). The latter is attributed to a low barrier for the entry of water molecules and large slip lengths inside graphene capillaries. Building on these findings, we demonstrate a simple scalable method to obtain graphene-based membranes with limited swelling, which exhibit 97% rejection for NaCl.
authors.affiliation: National Graphene Institute, University of Manchester, Manchester M13 9PL, UK.|School of Chemical Engineering and Analytical Science, University of Manchester, Manchester M13 9PL, UK.|School of Physics and Astronomy, University of Manchester, Manchester M13 9PL, UK.
authors.forename: Jijo
authors.initials: J
authors.lastname: Abraham
authors.affiliation: National Graphene Institute, University of Manchester, Manchester M13 9PL, UK.|School of Chemical Engineering and Analytical Science, University of Manchester, Manchester M13 9PL, UK.
authors.forename: Kalangi S
authors.initials: KS
authors.lastname: Vasu
authors.affiliation: School of Chemical Engineering and Analytical Science, University of Manchester, Manchester M13 9PL, UK.
authors.forename: Christopher D
authors.initials: CD
authors.lastname: Williams
authors.affiliation: School of Physics and Astronomy, University of Manchester, Manchester M13 9PL, UK.
authors.forename: Kalon
authors.initials: K
authors.lastname: Gopinadhan
authors.affiliation: National Graphene Institute, University of Manchester, Manchester M13 9PL, UK.|School of Chemical Engineering and Analytical Science, University of Manchester, Manchester M13 9PL, UK.
authors.forename: Yang
authors.initials: Y
authors.lastname: Su
authors.affiliation: National Graphene Institute, University of Manchester, Manchester M13 9PL, UK.|School of Chemical Engineering and Analytical Science, University of Manchester, Manchester M13 9PL, UK.
authors.forename: Christie T
authors.initials: CT
authors.lastname: Cherian
authors.affiliation: School of Chemical Engineering and Analytical Science, University of Manchester, Manchester M13 9PL, UK.
authors.forename: James
authors.initials: J
authors.lastname: Dix
authors.affiliation: School of Materials, University of Manchester, Manchester M13 9PL, UK.
authors.forename: Eric
authors.identifier: 0000-0003-1340-0970
authors.initials: E
authors.lastname: Prestat
authors.affiliation: School of Materials, University of Manchester, Manchester M13 9PL, UK.
authors.forename: Sarah J
authors.identifier: 0000-0001-5509-6706
authors.initials: SJ
authors.lastname: Haigh
authors.affiliation: National Graphene Institute, University of Manchester, Manchester M13 9PL, UK.
authors.forename: Irina V
authors.identifier: 0000-0001-5991-7778
authors.initials: IV
authors.lastname: Grigorieva
authors.affiliation: School of Chemical Engineering and Analytical Science, University of Manchester, Manchester M13 9PL, UK.
authors.forename: Paola
authors.initials: P
authors.lastname: Carbone
authors.affiliation: School of Physics and Astronomy, University of Manchester, Manchester M13 9PL, UK.
authors.forename: Andre K
authors.initials: AK
authors.lastname: Geim
authors.affiliation: National Graphene Institute, University of Manchester, Manchester M13 9PL, UK.|School of Chemical Engineering and Analytical Science, University of Manchester, Manchester M13 9PL, UK.
authors.forename: Rahul R
authors.initials: RR
authors.lastname: Nair