Rearrangement of π-electron network and switching of edge-localized π state in reduced graphene oxide.

Introduced defects can modulate the intrinsic electronic structure of graphene, causing a drastic switch in its electronic and magnetic properties, in which defect-induced localized π states near the Fermi level play an important role. Accordingly, considerable effort has been directed toward detailed characterization of the defect-induced state; however, identification of the chemical nature of the defect-induced state remains a challenge. Here, we demonstrate a method for reliable identification of the localized π states of oxidized vacancy edges in reduced graphene oxide. Depending on the dynamic changes in the oxygen-binding modes, i.e., between carbonyl and ether forms in the vacancy edges, the π-electron network near the edges can rearrange, leading to drastic on-off switching of the localized π state. This switching can be manipulated via scanning-probe-induced local mechanical force. This study provides fundamental guidance toward understanding how oxidized defect structures contribute to the unique electronic state of graphene oxide and its potential future applications in electronic devices.