A new route towards uniformly functionalized single-layer graphene

It is shown, by DFT calculations, that the uniform functionalization of the upper layer of graphite by hydrogen or fluorine does not change essentially its bonding energy with the underlying layers, whereas the functionalization by phenyl groups decreases the bonding energy by a factor of approximately ten. This means that the functionalized monolayer in the latter case can be easily separated by mild sonication. According to our computational results, such layers can be cleaned up to pure graphene, as well as functionalized further up to 25% coverage, without much difficulty. The energy gap within the interval from 0.5 to 3 eV can be obtained by such one-side funtionalization using different chemical species.