Green Synthesis of Less Defect Density Bilayer Graphene

Here we report a green way to synthesis less defect density bilayer graphene from exfoliated graphite. Exfoliated graphite has been synthesized by chemical intercalation of natural flake graphite through microwave irradiation. Maximum expanded volume of 150 ml/g and low bulk density of 11.1 × 10^–3 g/cc have been found in chemically intercalated graphite, which is processed at microwave irradiation power of 600 watt and 50 s irradiation time. This exfoliated graphite has been successfully converted into bilayer graphene with the addition of oxalic acid, which acts as a green reducing agent, followed by ultrasonication and heat treatment. Graphene sheets are characterized by Raman spectroscopy, X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and X-ray photoelectron spectroscopy (XPS). Raman analysis confirms the synthesis of bilayer graphene sheets as well as the defect density (η _D)∼8.90 × 10⁹ cm^–2.