The interaction with atomic oxygen converts the initially metallic CNTs into semiconducting, and that depending on the oxygen dose and reaction temperature the type and abundance of oxygenated functional groups formed changes significantly, including gasification and consumption of the CNTs at elevated temperatures. The most important finding is that the type and abundance of the groups formed and the gasification rate are strongly influenced by the density and size of vacancy defects in the graphene layers of the carbon nanotube. On one hand, this introduces uncertainties when analogous procedures are employed for

functionalization of CNTs with undefined density and types of defects, but on the other hand it prompts an approach for tailoring CNTs via controlled introduction of defects, which can favor the formation of a preferred functional group.