Nature 468, 549–552 (2010)

In this Letter, the assigned values for melamine XPS signals of 284.5 eV (C 1s) and 395.8 eV (N 1s) were incorrect (Supplementary Fig. 7). Repeating the melamine spectrum with a graphite additive standard (C 1s = 284.5 eV) showed that the assignments for melamine should be 286.8 eV (C1s) with N 1s in the ring at 397.8 eV and N 1s external to the ring at 398.7 eV. Therefore, the monolayer N-doped graphene on SiO2 substrates having signals of 284.5 eV (C 1s) and 399.8 eV (N 1s) remains clearly distinguished from the melamine starting material. Furthermore, the Li et al.1 (ref. 29 in this Letter) assignment for quaternary N was misquoted. Although high-temperature (1,000 °C) growth favours quaternary N in the N-doped graphene film (this is supported by ref. 1), our assignment of 399.8 eV (N 1s) for monolayer N-doped graphene is different from the Li et al.1 assignment, because their assignment of 401 eV (N 1s) is for thick N-doped graphene films. In our experiments, when we used poly(ethylene imine) as a growth source, multilayer N-doped graphene was attained and similarly gave 401.2 eV (N 1s) as the assignment. Therefore, either there is a difference between the thick film assignments of Li et al.1 and our assignment of monolayer N-doped graphene on SiO2 substrates, or the N signals in our material are more pyridinic and/or pyrrolic in content2. We thank T. Susi for bringing this to our attention.