The emergence of facile approaches for the large-scale production of graphene oxide (GO) membranes necessitates a clearer understanding of their potential to foul and, more importantly, strategies for efficient recovery of membrane performance following fouling. Here, we systematically investigated the feasibility of water, ethanol, and hypochlorite as cleaning agents to remove organic foulants over a GO membrane. Among them, 100 ppm hypochlorite solution showed a remarkable ability to remove bovine serum albumin (BSA) and could recover the membrane flux up to 98% after five cycles of BSA filtration and cleaning.
View Article and Find Full Text PDFSolvent transport in membranes composed of stacked sheets of graphene oxide (GO) with molecular scale channels and a complex arrangement of hydrophobic and hydrophilic domains is not well understood. Here, we observe that the interlayer space between GO sheets expands in different solvents without disturbing the membrane integrity and is typically larger in aqueous media compared to nonaqueous media. However, the membranes have a tighter molecule sieving feature in aqueous media as demonstrated by lower permeance and higher solute rejection arising from interfacial water layers "sticking" to charged polar groups.
View Article and Find Full Text PDFIontronic circuits are built using components which are analogous to those used in electronic circuits, however they involve the movement of ions in an electrolyte rather than electrons in a metal or semiconductor. Developments in these circuits' performance have led to applications in biological sensing, interfacing and drug delivery. While transistors, diodes and elementary logic circuits have been demonstrated for ionic circuits if more complex circuits are to be realized, the precident set by electrical circuits suggests that a component which is analogous to an electrical capacitor is required.
View Article and Find Full Text PDFUltrasensitive flexible strain sensors were developed through the combination of shear alignment of a high concentration graphene oxide (GO) dispersion with fast and precise patterning of multiple rectangular features on a flexible substrate. Resistive changes in the reduced GO films were investigated under various uniaxial strain cycles ranging from 0.025 to 2%, controlled with a motorized nanopositioning stage.
View Article and Find Full Text PDFGraphene-based membranes demonstrating ultrafast water transport, precise molecular sieving of gas and solvated molecules shows great promise as novel separation platforms; however, scale-up of these membranes to large-areas remains an unresolved problem. Here we demonstrate that the discotic nematic phase of graphene oxide (GO) can be shear aligned to form highly ordered, continuous, thin films of multi-layered GO on a support membrane by an industrially adaptable method to produce large-area membranes (13 × 14 cm(2)) in <5 s. Pressure driven transport data demonstrate high retention (>90%) for charged and uncharged organic probe molecules with a hydrated radius above 5 Å as well as modest (30-40%) retention of monovalent and divalent salts.
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