Facile synthesis of multi-layer graphene by electrochemical exfoliation using organic solvent

This paper presents a facile method of producing graphene nanosheets by organic liquid-assisted electrochemical exfoliation using tetramethyleammonium hydroxide (TMAH) as organic electrolyte. The process involves low-cost copper as ground electrode and carbon block as anode or cathode. The application of organic electrolyte eliminates the presence of unwanted metal ions on the graphene nanosheets. To the best of our knowledge, this is a maiden effort of producing graphene with pure organic electrolyte using TMAH with low-cost copper electrode. By the use of TMAH, conformal large-area graphene nanosheets of 4.3 nm thickness with an average sheet diameter of 3-4 mu m have been obtained. Graphene nanosheets are characterized by X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, ultraviolet-visible spectroscopy, Fourier transform infrared, Raman spectroscopy, and atomic force microscopy. Raman characterization confirms the conservation of the intrinsic nature of few-layer graphene. Graphene nanosheets are dissolved in a polar aprotic solvent dimethylformamide and are drop coated on the Si/SiO2 substrate to make a thin film of graphene. Films are annealed to remove any residual solvent attached to it. Different annealing temperatures (50-200 degrees C) were reported. Sheet resistances were measured before and annealing, with a remarkable decrease afterward. Current-voltage characteristics were studied to evaluate the conductivity of the graphene nanosheets produced.