Because the NP had been held overnight without heating, TNP was initially ramped to 1900 K to clean the NP by subliming ~0.7 MDa, corresponding to ~63% of a ML of carbon for a spherical NP of this mass. TNP was then reduced to 1500 K, near the peak of graphite NP reactivity toward O2, 1 and briefly exposed to 2 x 10 -5 Torr of O2 to see if the NP had remained passivated after the 1900 K sublimation period. A brief period of fast etching occurred (EEO2 just under 10 -3 Da/collision), showing that sublimation had reactivated the NP surface, however, after losing only ~300 kDa, the NP abruptly re-passivated (EEO2 <10 -6 Da/O2 collision). 300 kDa corresponds to less than a third of a complete carbon monolayer, thus the passivated (fullerenelike) surface layer was re-established after minimal etching.