Graphene Nanomesh by ZnO Nanorod Photocatalysts

Local photodegradation of graphene oxide sheets at the tip of ZnO nanorods was used to achieve semiconducting graphene nanomeshes. The chemically exfoliated graphene oxide sheets, with a thickness of approximately 0.9 nm, were deposited on quartz substrates. Vertically aligned ZnO nanorod arrays with diameters of 140 nm and lengths of <1 microm were grown on a glass substrate by using a hydrothermal method. The graphene oxide sheets were physically attached to the tip of the ZnO nanorods by assembling the sheets on the nanorods. UV-assisted photodegradation of the graphene oxide sheets (with dimension of approximately 5×5 microm) at a contact place with the ZnO nanorods resulted in graphene nanomeshes with a pore size of approximately 200 nm. The graphene nanomeshes prepared by using the photocatalytic property of the ZnO nanorods contained smaller oxygen-containing carbonaceous bonds and higher defects as compared to the as-prepared graphene oxide sheets. When chemical reduction of the graphene nanomeshes by hydrazine was used, the oxygen bonds of the nanomeshes more decreased while their graphitization increased. Based on X-ray photoelectron spectroscopy at low binding energies, the graphene nanomeshes reduced by hydrazine exhibited as a broad sheet a p-type semiconductor with an approximately 1.2 eV energy gap between the valence band and the Fermi level.