Within the nanopores, junctions and interlayer void space (IVS) in graphene oxide film (GOf), we report that IVS function as the key semipermeable site during sieving. The GOf could filter only dye molecules having nanometer-ranged dimensions. Tinier hydrated ions with angstrom-ranged dimensions couldn't be sieved by GOf. Nature and extent of this molecular sieving property have been justified by observing sieving efficacy and flow times for aqueous solutions of dyes, inorganic salts and their mixtures. GOf also could separate the dyes from mixtures with salts. The flow time followed the trend as: mixtures > salt solutions > dye solutions. PXRD data reveal entering of dye molecules at IVS during sieving. Obviously, a part of dye molecules leaking through the nanopores and junctions of GOf, finally become trapped at the IVS. IVS, therefore has been recognized as the key semipermeable site for molecular sieving in GO. With exploring the insight features of molecular sieving in GOf, this report clearly indicates that IVS needs to be tuned to adopt GOf for various analytical aspects including water purification, desalination and organic inorganic separation.
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