Size Fractionation of Graphene Oxide via Flow Field-Flow Fractionation for Reinforced Graphene Fiber

Many interesting properties of 2D materials and their assembled structures are strongly dependent on the lateral size and size distribution of 2D materials. Accordingly, effective size separation of polydisperse 2D sheets is critical for desirable applications. Here, we introduced flow field-flow fractionation (FlFFF) for wide-range size fractionation of graphene oxide (GO) up to 100 μm. Two different separation mechanisms are identified for FlFFF, including normal mode and steric/hyperlayer mode, to size fractionate wide size-distributed GOs while employing a crossflow field for either diffusion or size-controlled migration of GO. We confirmed the chemical composition and defect density of GO are directly proportional to its size. Using size fractionated GOs, three different graphene fibers were fabricated. The microstructure of graphene fibers is strongly affected by their building block size. We also investigated the 2D sheet size-dependent mechanical and electrical properties of three different graphene fibers produced from size-fractionated GOs. This FlFFF-based size selection methodology can be used as a generic approach for effective wide-range size separation for 2D materials, including rGO, TMDs, and MXene.