Precise and Ultrafast Molecular Sieving Through Graphene Oxide Membranes

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Science  14 Feb 2014:
Vol. 343, Issue 6172, pp. 752-754
DOI: 10.1126/science.1245711

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  1. Fig. 1 Ion permeation through GO laminates.

    (A) Photograph of a GO membrane covering a 1-cm opening in a copper foil. (B) Schematic of the experimental setup. A U-shaped tube 2.5 cm in diameter is divided by the GO membrane into two compartments referred to as feed and permeate. Each is filled to a typical level of ∼20 cm. Magnetic stirring is used so as to ensure no concentration gradients. (C) Permeation through a 5-μm-thick GO membrane from the feed compartment with a 0.2 M solution of MgCl2. (Inset) Permeation rates as a function of C in the feed solution. Within our experimental accuracy (variations by a factor of <40% for membranes prepared from different GO suspensions), chloride rates were found the same for MgCl2, KCl, and CuCl2. Dotted lines are linear fits.

  2. Fig. 2 Sieving through the atomic-scale mesh.

    The shown permeation rates are normalized per 1 M feed solution and measured by using 5-μm-thick membranes. Some of the tested chemicals are named here; the others can be found in table S1 (25). No permeation could be detected for the solutes shown within the gray area during measurements lasting for at least 10 days. The thick arrows indicate our detection limit, which depends on a solute. Several other large molecules—including benzoic acid, DMSO, and toluene—were also tested and exhibited no detectable permeation. The dashed curve is a guide to the eye, showing an exponentially sharp cutoff at 4.5 Å, with a width of ≈0.1 Å.

  3. Fig. 3 Simulations of molecular sieving.

    (A) Snapshot of NaCl diffusion through a 9 Å graphene slit allowing two layers of water. Na+ and Cl ions are in yellow and blue, respectively. (B) Permeation rates for NaCl, CuCl2, MgCl2, propanol, toluene, and octanol for such capillaries. For octanol poorly dissolved in water, the hydrated radius is not known, and we use its molecular radius. Blue marks indicate permeation cutoff for an atomic cluster (inset) for graphene capillaries accommodating two and three layers of water (widths of 9 and 13 Å, respectively).

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