A novel approach towards selective bulk synthesis of delaminated graphenes in an electric arc

Abstract: Here we demonstrate the selective bulk scale synthesis of delaminated graphene sheets by a proper choice of magnetic field modulating an electric-arc. An ultra-high purity glassy graphite anode was sublimated in an argon atmosphere. Carbon nanotubes, as well as graphene sheets were found inside the deposit formed on the cathode. Both the high purity carbon nanotubes as well as graphene sheets, with minimal structural defects, were synthesized separately by varying the strength and orientation of the external magnetic field generated by arrays of permanent magnets. The as-synthesized carbonaceous samples were characterized with the help of transmission electron microscopy, selected area electron diffraction, Raman spectroscopy and thermogravimetry for optimizing the highest selective production of delaminated graphenes. This optimization was done by varying the strength and orientation of the external magnetic field. The as-synthesized graphene sheets exhibited relatively high degree of graphitization and low structural defect density as confirmed by RS. They were found to exhibit higher oxidation temperature than that of the carbon nanocrystalline particles as inferred from the thermogravimatric analysis. Moreover, they were found to form scroll-like carbon nanotubes at their edges on account of their surface energy minimization. This was confirmed by the selected area electron diffraction analysis. With this new technique, we could successfully synthesize delaminated graphenes at a rate of few grams per hour.