Azidated Graphene: Direct Azidation from Monolayers, Click Chemistry, and Bulk Production from Graphite

The inertness of the graphene basal plane has notably limited its viable chemical modification pathways. We report direct azidation and subsequent click chemistry of the graphene basal plane through the electrochemical oxidation of an aqueous sodium azide solution at the graphene surface. An ∼20% nitrogen-to-carbon ratio is achieved for monolayer graphene under ambient conditions and neutral pH, and the degree of functionalization is tunable through the applied voltage. The functionalized azide groups enable both copper-catalyzed and copper-free alkyne cycloaddition click chemistry, as well as subsequent bioconjugation, and fluorescence microscopy indicates uniform functionalization across the graphene surface. Notably, we find that as the azidation, cycloaddition, and bioconjugation processes substantially shift the graphene doping level, high electrical conductivity and carrier mobility are maintained throughout the different functionalization states. By integrating the electrochemical azidation scheme with electrochemical exfoliation, we further demonstrate one-step bulk production of azidated graphene flakes from graphite. We thus open a new door to the facile preparation of diverse graphene derivatives under ambient conditions.