Pronounced, Reversible, and in Situ Modification of the Electronic Structure of Graphene Oxide via Buckling below 160 K

Abstract

We have shown that the electronic structure of graphene oxide is strongly, but reversibly, affected by temperature. Below 160 K, graphene oxide is much more completely oxidized, removing any last remaining π-conjugated network. Through DFT simulations, we have shown that this is due to buckling-induced oxidation. As temperature is reduced, the lightly oxidized, graphene-like zones attempt to expand due to a negative thermal expansion coefficient (TEC), but the heavily oxidized zones, with a TEC that is near zero, prevent this from happening. This contributes to localized buckling. The deformed regions oxidize much more readily, and the 1,2-epoxide groups form a new type of functional group never before seen: a triply bonded oxygen, bonded at the 1,3,5 sites of the hexagonal carbon rings. We have called this group TB-epoxide. Stable only under buckling, the TB-epoxide groups revert back to 1,2-epoxides once the lattice relaxes to a flatter profile. We have shown that one can alter the electronic structure of graphene oxide to induce temporary, but more complete, oxidation via strain.