Defect formation in graphene nanosheets by acid treatment: an x-ray absorption spectroscopy and density functional theory study

In-plane defects have been introduced into graphene nanosheets by treatment with hydrochloric acid. Acid treatment induces bond cleavage in the C-C network via electrophilic attack. These resultant vacancy sites will then undergo further reactions with the surrounding ambient to produce C-O and C-H bonds. A sigma* resonance at 287 eV in the carbon K-edge x-ray absorption spectra is observed with acid treatment and is assigned to C-O states. Theoretical modelling of a di-vacancy in a graphene bilayer reproduces all essential features of this resonance and in addition predicts a metallic conductivity of states around this vacancy. The possibility of engineering the properties of graphene via the routes explored here is an important step towards establishing strategies for building devices based on this material.