Eco-friendly and mechanochemically functionalised graphene with quick and high water dispersibility

Abstract

The exceptional electrical, mechanical and thermal properties of graphene have sparked the formation of a large body of research. Among these synthesis methods developed, there are trade-offs between increased processability and maintaining the unique properties of graphene. Previous work has utilised ball-milling which results in high yielding, low defect graphene with poor processibility, whereas liquid exfoliation of graphite in the presence of a surfactant gives highly dispersible graphene but with low concentration in a dispersed form which is unwieldy for transport and use. Herein, we describe an environmentally sound method to form graphene utilising the best of these two techniques, by ball-milling expanded graphite in the presence of the vitamin B₂ derivative Riboflavin Mononucleotide (FMN) to give a covalently bonded, highly dispersible (up to 100 mg ml⁻¹, stable for days), low defect graphene. FMN not only facilitated exfoliation of graphite to graphene, but also ensured colloidal stability of the graphene sheets in aqueous dispersions through functionalisation. This graphene formed through the principles of green chemistry will be useful in composites and additive free inks, particularly in bio applications as FMN is seen to confer increased biocompatibility to graphene in previous literature.