Structural Investigation of Carbon Nanoplatelets by Graphene Layers self-assembling

Low dimensional carbon based materials are strictly dependent from the intrinsic property of self-assembling. Three simple and fast methods to unzip Single Wall Carbon Nanotubes (SWCNTs) have provided different structural organization of graphite layers,[1] observed by electron microscopy investigations. The graphitic nanoplates were obtained from disruption of SWCNTs by using high-shear mixing and/or treatments in sulfonitric mixtures either at room or high temperatures. Depending on the process procedures, different kinds of re-organization are found to occur, as evidenced by different and complementary electron diffraction and microscopy techniques. To obtain insight into the local nano-structure of self-assembling of the graphitic phases produced from SWCNTs, transmission electron microscopy (TEM) has been used to characterize the morphology arrangement and the crystallinity identifications by Reflection High Energy Electron Diffraction (RHEED).[2] Detailed internal structural investigation has been achieved by selected area electron diffraction (SAED) and with help of its electron diffraction simulation. Here, we focused our investigation on the structural characterization of self-assembling graphitic layers that it has been and it is a long-standing scientific problem. Unlike crystalline system, where long-range ordering is established by periodic stacking of fundamental building blocks, known as unit cells, rolled open SWCNTs process produces graphitic flakes, having no long-range translational or orientational order, although some degrees of short- and medium-range order do exist. Our structural studies reveal the presence of a deviation from perfect crystal of the graphite aggregations, called turbostratic graphite, because of the presence of rotational and/or translational stacking faults of its hexagonal basal planes. Another interesting outcome of our research is that experimental evidences using electron diffraction technique indicate the existence of an unstable crystallographic phase of graphite with an orthorhombic cell and symmetry Cmma, detected by SAED and RHEED analysis and simulated by using the unit cell parameters reported by previously theoretical studies [3]. The last case study clearly confirms that EDPs are very sensitive to small variations in periodic structure or lattice imperfection and to investigate phase transition phenomena. Moreover, this research also intends to provide the readers with useful informations that to resolve the fundamental problem of how is thick a bi-dimensional structures of also different atomic species, TEM imaging analysis of the flake-edges must be coupled with electron diffraction pattern investigations