High-concentration shear-exfoliated colloidal dispersion of surfactant–polymer-stabilized few-layer graphene sheets

To exploit the remarkable properties of graphene fully, an efficient large-scale production method is required. Sonication-assisted liquid-phase exfoliation of graphite, for example, has been extensively used for the production of few-layer graphene sheets, but suffers from low efficiency and high energy consumption and thus is not viable for large-scale production. Here we demonstrate a method that is more efficient and has higher scalability potential than sonication. We show that a few-layer graphene at high concentration of up to 1.1 mg ml⁻¹ can be achieved in aqueous-based medium by highly efficient shear exfoliation of graphite in a processing time of just 2 h. The exfoliation process was carried out in a commercially available high shear colloidal mixer fixed with a three-stage rotor–stator shear generator for optimum exfoliation with a continuous circulation system. The high efficiency and a significant improvement over sonication adopting our method were demonstrated by the fact that the conversion to few-layer graphene sheets produced after just 30 min by shear exfoliation required, in contrast, 100s of hours by sonication. High-concentration defect-free few-layer graphene in aqueous medium, produced at short shearing time, demonstrates that this method has high potential for large-scale production. The produced graphene films exhibit additionally a high electrical conductivity of about 29000 S m⁻¹.