A single-atom-thick sheet of hexagonally arranged, bonded carbon atoms, either freely suspended or adhered to a substrate. The dimensions of graphene can vary from several nanometres to the macroscale. Monolayer (single-layer) graphene is the purest form available and is useful for high-frequency electronics. Bi- and tri-layer graphene, two and three layers respectively, display a range of different qualities as the number of layers increase, as well as becoming progressively cheaper as the layers multiply.
Multi-layer Graphene (MLG) or Few-layer Graphene (FLG)
A 2D, sheet-like material, either as a free-standing flake or substrate-bound coating, consisting of a small number (between two and about 10) of well-defined, countable, stacked graphene layers of extended lateral dimension. Individual flakes should still maintain a high aspect ratio. Few-layer graphene or graphene oxide dispersions can have a defined thickness distribution. MLG is useful for composite materials, and as a mechanical reinforcement.
Graphene Oxide (GO)
Chemically modified graphene prepared by oxidation and exfoliation. Graphene oxide is a monolayer material with a high oxygen content. Thin membranes that allow water to pass through but block off harmful gases are a major use for GO.
Reduced Graphene Oxide (rGO)
Graphene oxide (as above) that has been reductively processed by chemical, thermal, microwave, photo-chemical, photothermal or microbial/bacterial methods to reduce its oxygen content. Conductive inks are just one potential use for rGO.
Single-Walled Carbon Nanotubes (SWCN)
A Carbon Nanotube is a tube-shaped material, made of carbon, with the diameter measured on the nanometer scale. A nanometer is one-billionth of a metre, or about one ten-thousandth of the thickness of a human hair. The graphite layer appears somewhat like a rolled-up chicken wire with a continuous unbroken hexagonal mesh and carbon molecules at the apexes of the hexagons.
Carbon Nanotubes have many structures, differing in length, thickness and the number of layers. Although they are formed from essentially the same graphite sheet, their electrical characteristics differ depending on these variations, acting either as metals or as semiconductors.
As a group, Carbon Nanotubes typically have diameters ranging from <1 nm up to 50 nm.
Multi-Walled Carbon Nanotubes (MWCN)
Multi-Wall Nanotubes can appear either in the form of a coaxial assembly of Single-Wall Nanotubes that similar to a coaxial cable, or as a single sheet of graphite rolled into the shape of a scroll.
The diameters of Multi-Wall Nanotubes are typically in the range of 5nm to 50nm. The interlayer distance in Multi-Wall Nanotubes is close to the distance between graphene layers in graphite.