As noted, the smallest graphite and graphene oxide NPs were, by large factors, the least reactive NPs for each material. (The other low EEO2 cases were diamond or nano-onion NPs which had been pre-treated in ways that we expect to suppress reactivity). Low reactivity could be interpreted to indicate that graphitic NPs with mass in the ~10 MDa range are inherently less reactive than even slightly larger graphitic NPs, however, as discussed above, the graphitic structure should always expose large numbers of reactive edge/defect sites. An alternative explanation might be that these small graphitic NPs, or at least their surface layers, evolved more rapidly during the 1900 K sublimation periods than larger NPs, such that they had already lost most of their under-coordinated surface sites before EEO2 was measured. Faster restructuring for small NPs is not unreasonable, because they have a larger fraction of their atoms in surface sites where diffusion/isomerization barriers are lower because coordination is lower.