Fig. shows the evolution of a graphene oxide NP under conditions identical to those in Fig. , and also plotted identically. The NP was briefly heated to 1900 K, which should be sufficient to desorb all the oxygen surface functional groups, leaving a highly defective graphene NP (i.e., reduced graphene oxide), with mass of ~37.6 MDa. TNP was held at 1500 K for a total of 22 hours, the first 16 of which are shown. After measuring Rbase in argon, 4.3 x 10 -5 Torr of O2 was added (cyan background), leading to rapid etching (EEO2 ~1.1 x 10 -3 Da/O2 collision) that continued at nearconstant rate (I -IX) for ~3 hours as the NP lost ~16% of its initial mass. At that point, the mass loss slowed abruptly but continued for the next 12 hours at an average rate near 10 -4 Da/O2 collision, but with significant oscillations, including two periods with EEO2 < 10 -6 . At ~16 hours, EEO2 dropped below 10 -6 Da/O2 collision and remained there until the experiment was terminated at the ~22 hour mark. The total mass lost was ~20%, most of which occurred during the initial ~3 hours.