PerspectiveMaterials Science

Graphene Oxide Membranes for Ionic and Molecular Sieving

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Science  14 Feb 2014:
Vol. 343, Issue 6172, pp. 740-742
DOI: 10.1126/science.1250247

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Ionic and molecular sieving membranes that enable fast solute separations from aqueous solutions are essential for processes such as water purification and desalination, sensing, and energy production (13). The two-dimensional structure and tunable physicochemical properties of graphene oxide (GO) offer an exciting opportunity to make a fundamentally new class of sieving membranes by stacking GO nanosheets (46). In the layered GO membrane, water molecules permeate through the interconnected nanochannels formed between GO nanosheets and follow a tortuous path primarily over the hydrophobic nonoxidized surface rather than the hydrophilic oxidized region of GO (7). The nearly frictionless surface of the non-oxidized GO facilitates the extremely fast flow of water molecules (5). On page 752 of this issue, Joshi et al. (8) further report that ions smaller in size than the GO nanochannel can permeate in the GO membrane at a speed orders of magnitude faster than would occur through simple diffusion. Size exclusion appears to be the dominant sieving mechanism.