O 2 Oxidation Experiments on Pre-heated Silica NPs Fig. shows a variable TNP oxidation experiment for a silica NP, done using a similar protocol to analogous experiments done on Si NPs. The NP was CO2 laser pre-heated briefly as it was trapped, and then Q-stepped prior to the start of the data record shown. Minitial was 37.4 MDa Fig. shows the Roxid values extracted from the differences in slopes with and without O2 added. The left axis reports the kinetics as surface-area-normalized rates, as discussed above.