Determining the structure of graphene-based flakes from their morphotype

Graphene-based flakes of various origins were investigated by transmission electron microscopy. For each of them, the morphotype was described, and then both the related structure (stacking type) and nanotexture (degree of perfection of the graphene layers) were described as well. Two kinds of clearly discriminated morphotypes were found ('crumpled' and 'folded'), for objects with similar overall dimensions (in the range of several micrometers large) and similar multi-graphene nature (with the number of stacked graphene layers in the range of 2-15, sometimes more). It is found that the morphological discrepancies relate to the structural discrepancies. Typically, whether the structure is either turbostratic or graphitic makes the flake morphotype be either crumpled or folded, as a consequence of preferred folding directions related to lattice periodicities. In this regard, structure prevails over nanotexture. This strict relationship implies that the 2D (turbostratic) or 3D (graphitic) nature of the stacking in graphene-based flakes whose determination usually requires diffraction studies may be merely deduced from low magnification images of their morphotypes.

Examples of two graphene flakes with typical, different morpho-types (left: folded; right crumpled) whose occurrence relates to the graphene stacking type (graphitic, or turbostratic).227