Aqueous-based bromination of graphene by electrophilic substitution reaction: a defect-free approach for graphene functionalization

A simple and effective approach for covalent bromination of reduced graphene oxide (RGO) using N -bromosuccinimide (NBS) in aqueous solution is reported. We postulate that this was achieved by using sulfuric acid to decompose NBS and facilitate the formation of bromine cations, which in turn acted as electrophilic reagents and covalently bonded to the defect sites (mostly sp 2 C–H) graphene sheets via electrophilic substitution reaction. The bonding situation and the content of bromine in the obtained brominated RGO (RGO-Br) were characterized using FTIR, XPS, EDS, and TGA techniques. The structure and morphology changes of the graphene sheets were also characterized by SEM, TEM, AFM, and Raman. The results show that the RGO sheets were functionalized with a high bromine content (~ 7.28 at%) and without further damaging the conjugated structure. Considering that C–Br functional groups can be further modified by a variety of organic functional groups, RGO-Br could be used as a promising intermediate in the synthesis of other functional graphene materials for various potential applications.