Plasma-engineered GQD-inorganic membranes with tunable interactions for ultrahigh-efficiency molecular separations

Abstract

Ultrahigh-efficiency molecular separation (MS) membranes with tunable size-selective molecular separation, chemical-mechanical robustness, and long-term stabilities are useful for fundamental studies and applications. However, conventional MS membranes are hampered by the problems of uncontrolled molecular interactions, low separation efficiency, and energy and time-consuming fabrications. Here, we show an effective plasma engineering of nitrogen doped graphene quantum dot (NGQD)-inorganic nanocomposites composed with NGQDs and alumina-based hollow fibers (AHFs) with controlled properties and tunable local physicochemical environments for size-selective molecular separations. Detailed spectroscopic study and membrane characterization suggest that the plasma-synthesized NGQDs with defined zero-dimensional (0D) carbon-based sp2 hybridization, tunable nitrogen dopants and surface functional groups can affect the properties of the GQD-inorganic nanocomposites, therefore controlling molecular separation between the nanocomposites and molecules with different dye molecular weights (MWs). Moreover, the NGQDs can further induce the formation of nanochannel and control the nanopore structures of the nanocomposites, leading a significant molecular separation performance with a high 92.68 separation factor (S) for the mixed molecules with a 200 Da MW difference and a high water permeability up to 36.64 L m−2 h−1 bar−1. Our work provides a step for the engineering of functional nanocomposites for fundamental studies of molecular transport and emerging applications including catalysis, green energy, optoelectronics, biomedical and environmental applications.