Correlation between defect density in mechanically milled graphite and total oxygen content of graphene oxide produced from oxidizing the milled graphite.

It has been reported that defect density in ball-milled graphite lattice increases with the milling time. Guided by this, we hypothesized that the oxygen content of graphene oxide can be substantially enhanced by oxidizing ball-milled graphite and also, the oxygen content would monotonically increase with the milling time as the defect sites would be preferred sites for oxidation. Interestingly, we observed that this correlation was not directly proportional for all milling hours. Even though, the defect density of graphite monotonically increased with milling time, the oxygen content of graphene oxide initially increased and then decreased. This was due to milling time dependent change in the size of the graphite plates and consequent relative abundance of the different oxygen containing functional groups on graphene oxide (GO) produced from the milled graphite.