Engineering graphene by oxidation: a first-principles study.

Graphene epoxide, with oxygen atoms lining up on pristine graphene sheets, is investigated theoretically here using first-principles calculations. Two distinct phases-metastable clamped and stable unzipped structures-are observed consistent with experimental observations. In the clamped structure, oxygen atoms form a regular lattice on the graphene sheet. In the unzipped phase, an epoxy group breaks the lower sp(2) bond and modifies the mechanical and electronic properties of graphene remarkably. The foldable epoxy ring structure reduces its Young's modulus by 42.4%, while leaving the tensile strength almost unchanged. The perturbation of epoxidation on the band structures depends on the density and symmetry of oxidation. These results pave the way for oxidation-based engineering of graphene-related materials.