For perfect, defect-free multi-layer nano-onions, one might expect that the stability of the nested shells could be high enough to completely stop carbon atom loss for certain "magic" NP sizes, however, this was never observed. Note, however, that even after etching to the point of O2-inertness, our NPs were still relatively large, containing >500,000 atoms. For such large onions at high TNP, there must be large ensembles of thermally accessible isomers at high TNP, and enough thermal energy to drive isomerization, thus trapping into a single (or small number of) perfect inert structure(s) would be unlikely.