Comparing the etching kinetics for CO2 laser pre-heated silica and Si NPs under identical conditions provides additional insight into both the structure of the pre-heated silica NPs, and to the role of subsurface oxygen in the passivation process. For elemental Si NPs, the NP core is essentially oxygen free, and after pre-heating well above Tmelt, the NP surface layer should also initially be free of contaminants, including Oads because of desorption during pre-heating. Preheated silica NPs clearly also have Si-rich surface layers, but may retain significant O concentration in the subsurface. The pre-heated silica experiments, therefore, provide a different vantage point from which to probe high temperature oxidation of Si-rich NPs.