Hyperstage Graphite: Electrochemical Synthesis and Spontaneous Reactive Exfoliation

Abstract

Covalent modification of the π-electron basal planes of graphene enables the formation of new materials with enhanced functionality. An electrochemical method is reported for the formation of what is referred to as a Hyperstage-1 graphite intercalation compound (GIC), which has a very large interlayer spacing d[subscript 001] > 15.3 Å and contains disordered interstitial molecules/ions. This material is highly activated and undergoes spontaneous exfoliation when reacted with diazonium ions to produce soluble graphenes with high functionalization densities of one pendant aromatic ring for every 12 graphene carbons. Critical to achieving high functionalization density is the Hyperstage-1 GIC state, a weakening of the van der Waals coupling between adjacent graphene layers, and the ability of reactants to diffuse into the disordered intercalate phase between the layers. Graphene functionalization with 3,5-dinitrophenyl groups provides for exceptional dispersibility (0.24 mg mL[superscript −1]) in N,N-dimethylformamide and for conjugation with amines.