Characterization of carbon structures produced by graphene self-assembly

Low-dimensional carbon-based materials, in particular two-dimensional graphenic carbon structures, have been produced from single-walled carbon nanotube disruption using high-shear mixing and/or treatments in sulfonitric acid mixtures at both room and high temperature. Among other two-dimensional graphenic carbon structures, colloidal dispersions of graphenic nanoflakes have been obtained. Different structural arrangements, resulting from the reorganization of carbon because of the disruption procedures applied, were observed through selected area electron diffraction (SAED) and through reflection high-energy electron diffraction (RHEED) analyses coupled to transmission and scanning electron microscopy observations. Such combined investigations in the real and reciprocal space provided structural information at the nanoscale on the clustering of graphene layers in nanoplatelets or/and on their assembly into highly ordered (single-crystal) nanosheets. Furthermore, a different carbon phase exhibiting an orthorhombic cell with Cmma symmetry has been detected by SAED and RHEED analyses. In addition, a variety of self-assemblies of hexagonal basal planes have been observed to occur as the result of their different rotational and/or translational stacking faults. Overall, the reported results contribute to define the conditions for a controlled self-assembly of graphene-based structures with tailored dimensions, which is an important technological challenge, as their structure at the nanoscale dramatically affects their electrical properties.