A novel approach towards selective bulk synthesis of few-layer graphenes in an electric arc

The paper demonstrates the selective bulk synthesis of few-layer graphenes by optimizing an external magnetic field assisted electric arc. An ultra-high purity glassy graphite anode was sublimated in an argon atmosphere, and carbon nanotubes (CNTs), along with graphene sheets, were found inside the deposit formed on the cathode. Both the high purity CNTs and the graphene sheets, with minimal structural defects, were synthesized separately by varying the strength and orientation of the external magnetic field. The as-synthesized carbonaceous samples were characterized with the help of transmission electron microscopy, selected area electron diffraction (SAED), Raman spectroscopy and thermogravimetry with the objective of optimizing the highest selective production of 2D graphene structures. The as-synthesized graphene sheets exhibited a relatively high degree of graphitization and low structural defect density as confirmed by Raman spectroscopy. They were found to exhibit higher oxidation temperature (767 deg C) than that of the carbon nanocrystalline particles (690 deg C), as inferred from the thermogravimatric analysis. Moreover, they were found to roll up at their edges on account of their surface energy minimization. This was confirmed by the SAED analysis. With this new technique, we could successfully synthesize 2D graphene structures at the rate of a few g h-1.