To recap, Graphene has extraordinary material properties including an ultimate tensile strength of 130 gigapascal, an electron mobility of 15,000 cm2.V-1.s-1, a thermal conductivity between 2000–4000 W m-1K-1 and an optical transparency of 97.7%. (Fullerex Report, 2017).
These unique properties explain the proliferation of production processes that have been developed in an attempt to create this paradigmatic material, resulting in the emergence of a broad spectrum of graphene-based materials. These materials range from a single layer of carbon atoms to those comprising tens or even hundreds of layers in a stack, essentially Nano-graphite.
While the strict definition of graphene is that of a monolayer material, generally, the thicker the graphene material the less exceptional its properties become. Accordingly, as one moves from multi-layer to monolayer across the broad range of graphene materials, the overall mechanical and conductive properties of the material increase, as well as surface area per unit weight and overall cost and time to produce. In addition to the number of layers, there are also significant property changes that arise from any intrinsic defects in the crystalline structure (dislocations, tears and grain boundaries), and/or extrinsic defects (chemical impurities such as foreign atoms), where such defects limit the benefits of using graphene.
The ‘holy grail’, therefore, is the ability to produce industrial volumes of pristine single-layered (or very few-layered) sheets of graphene for a reasonably low cost.