Ultrahigh concentration exfoliation and aqueous dispersion of few-layer graphene by excluded volume effect

Colloidal properties of nanoparticles are intricately linked to their morphology. Traditionally, achieving high-concentration dispersions of two-dimensional (2D) nanosheets has proven challenging as they tend to agglomerate or re-stack under increased surface contact and Van der Waals attraction. Here, we unveil an excluded volume effect enabled by 2D morphology, which can be coupled with electrostatic repulsion to synthesize high-concentration aqueous graphene dispersions. To achieve this, we designed a sequential process involving edge oxidation, bubble expansion and mechanical shearing, through which graphite flakes were exfoliated into aqueous dispersions with ~94.5 wt.% yield of few-layer graphene, high concentration exceeding 100 mg mL