UV-light-assisted oxidative sp³ hybridization of graphene

We report the transformation of electronic structures of sp² graphene to sp³ graphene by UV-light-assisted oxidation. Two distinctive oxidation mechanisms were observed during this metalinsulator transition: (i) At low-oxidation regime, p-doping behavior by oxygen species extracting electrons from graphene and (ii) at high-oxidation regime, n-doping behavior by electron-hopping via strongly localized oxide states. We also found that the dominant oxygen-related functional group by UV-light-assisted oxidation was an epoxide group rather than hydroxyl group, which differed from conventional graphite oxide.