Nanochannel regulation of graphene quantum dots composite membranes via electrospray assisted self-assembly method

Nanochannel construction and regulation of graphene-based composite films are critical to the efficient separation performance. We report on a novel approach to preparing porous graphene-based composite films based on electrospray assisted self-assembly method by intercalating diamine monomers between graphene quantum dots (GQDs) nanosheets. Four kinds of diamine monomers were chosen as the bridging agents to fine tune the nanochannels between GQDs nanosheets. The physicochemical structures of as-prepared GQDs composite membranes were further optimized by post-crosslinking. The results showed that the covalent reactions of GQDs nanosheets with diamine monomers were occurred simultaneously between parallel and perpendicular GQDs nanosheets in the membrane preparation process, which constructed the three-dimensional space architecture of the GQDs composite membrane. The diamine monomers with different structures and molecular weights could change the loose structures of the separation layers, which endowed the GQDs composite membranes with the adjustable pore size and better hydrophilicity, further affecting their dye desalination performance. With the increase of the molecular weight of diamine monomers, the pore size of GQDs composite membranes increased slightly from 3.4 nm (GQDs-EDA) to 3.8 nm (GQDs-PPD), while the dye rejection decreased slightly. This study provided an insight into the uniform self-assembly of GQDs into nanofilms to fine tune the nanochannel structure.