Tuning the nature of nitrogen atoms in N-containing reduced graphene oxide

Physical and chemical properties of graphene can be tailored by nitrogen doping. As a consequence of the continuous race to achieve the highest possible amount of doping there is a growing tendency to assume that all N species are incorporated within the graphene lattice (doping). Here we show that this is not always the case and employ several complementary techniques that allow a proper assessment of the type of nitrogen present. The nature of the nitrogen atoms has been tuned by ammonolysis of graphene oxide in the range of 100 °C-800 °C. This allows us to expand the capabilities of the synthetic approach to afford not only N-doping (at high temperature) but also to introduce amine and amide moieties at 100 °C; the latter presenting a much higher dispersability in aqueous media than graphene oxide. Interestingly, the sample with the highest amount of nitrogen (14.7 wt. %) cannot be referred to as N-doped graphene since it also contains N-bearing aliphatic moieties.