Synthesis of Hydrogenated Graphite Nanostructures and Their Size-dependent Photoluminescence

Hydrogenated graphite/graphene nanostructures (HGNSs) were synthesized via a solvothermal route at 180 degrees C using potassium as the reductant and halogenobenzene(bromobenzene and dibromobenzene) as the carbon precursor. Selective cleavage of the relatively lower stable C-Br bonds(compared to C-H bonds) of the carbon precursor(C6H5Br and C6H4Br2, respectively) by K metal results in the growth of hydrogenated carbon nanostructures. The HGNSs grow through the polymerization and bonding of the remained hexagonal carbon rings after the debromination. The samples synthesized using C6H5Br and C6H4Br2 as carbon precursor are visually tawny and black, respectively. Raman and infrared spectra of the samples show that the black product is hydrogenated graphite nanosheets with the size of about 2 nm, while the tawny sample has smaller size. X-Ray diffraction(XRD) measurements show that the products are stacked in a rhombohedral structure, but with low crystallinity. Photoluminescence(PL) measurements of the samples reveal that the fluorescence intensity and energy are related to the size of the formed HGNSs. The fluorescence intensity of the tawny product is about 15 times higher than that of the black one under the same experimental conditions. A photoluminescence mechanism similar to that of graphite oxide has been proposed for the HGNSs.