Tuning Structural Defects on a Nominal Single-Layered Graphene Oxide Membrane for Selective Separation of Biomolecules

Two-dimensional (2D) materials provide a great opportunityforfabricating ideal membranes with ultrathin thickness for high-throughputseparation. Graphene oxide (GO), owing to its hydrophilicity and functionality,has been extensively studied for membrane applications. However, fabricationof single-layered GO-based membranes utilizing structural defectsfor molecular permeation is still a great challenge. Optimizationof the deposition methodology of GO flakes could offer a potentialsolution for fabricating desired nominal single-layered (NSL) membranesthat can offer a dominant and controllable flow through structuraldefects of GO. In this study, a sequential coating methodology wasadopted for depositing a NSL GO membrane, which is expected to haveno or minimum stacking of GO flakes and thus ensure GO's structuraldefects as the major transport pathway. We have demonstrated effectiverejection of different model proteins (bovine serum albumin (BSA),lysozyme, and immunoglobulin G (IgG)) by tuning the structural defectsize via oxygen plasma etching. By generating appropriate structuraldefects, similar-sized proteins (myoglobin and lysozyme; molecularweight ratio (MWR): & SIM;1.14) were effectively separated witha separation factor of & SIM;6 and purity of 92%. These findingsmay provide new opportunities of using GO flakes for fabricating NSLmembranes with tunable pores for applications in the biotechnologyindustry.