Exfoliation of high-quality graphene in volatile and nonvolatile solvents

High-quality few-layer to multilayer graphene sheets were exfoliated in N , N -dimethylformamide (DMF) and 1-propanol by simple liquid-phase exfoliation method. Effect of sonication time on the yield and quality of graphene exfoliated in DMF has been studied. The graphene synthesized in 1-propanol and DMF was characterized and compared with one another. The graphene concentration achieved after 8 h of sonication in DMF and 1-propanol was 115 and 69 µg/ml, respectively. The graphene dispersion in DMF and 1-propanol consisted of flakes with thickness of ~2.7 and ~4 nm, respectively. Structural quality of the graphene synthesized in both the solvents was further investigated by Raman spectroscopy and Raman intensity mapping. Graphene sheets exfoliated in DMF and 1-propanol showed the electrical conductivity of 1172 and 224 S/m, respectively, at room temperature. These results revealed that defect-free bilayer graphene (BLG) to few-layer graphene (FLG) and multilayer graphene (MLG) were produced in DMF and 1-propanol, respectively.