The Many Forms of Graphene

In its traditional form, graphene is one atomic layer thick and usually exists as a film of sorts; however, the proliferation of graphene research and testing has led to the creation of various graphene forms, each used for unique purposes. These forms include graphene films produced through chemical vapor deposition (CVD), graphene oxide (GO), reduced graphene oxide (rGO) and graphene nanoplates (GNPS).

CVD

A graphene film is a thin (one atom thick) sheet of carbon atoms that are densely packed in a hexagonal lattice. This film can be produced in numerous ways, such as mechanical and thermal exfoliation, epitaxial growth, and chemical reduction. However, chemical vapor deposition (CVD) is the most common method used in production today. CVD begins in a gas chamber, where gas molecules are combined and placed onto a substrate.

While in the chamber, materials form on the surface of the substrate; and then high-levels of heat are used to assemble the dissociated carbon atoms onto the substrate, creating a single carbon layer. This entire process is highly dependent upon temperature. In fact, variations in temperature may alter the chemical interaction taking place within the chamber.

GO

Our team at GraphenTech specializes in Graphene Oxide (GO). A substance most commonly produced by the oxidizing graphite. Through oxidation, graphene is modified with a carbon-to-oxygen ratio between 3.0 and 2.0. Oxidation also enhances the layers of graphene. Among these enhancements is hydrophilicity; due to hydrophilicity, graphene can remain highly stable even when dispersed in water or other solvents. GO also has high-levels of electrons. The downside of the GO form of graphene is that it loses oxide each time conductivity occurs.

rGO

Our team also specializes in the production of reduced graphene oxide (rGO). There are numerous ways to produce rGO such as annealing, hydrazine vapor treatment, and microwave reduction. But the majority fall into three main categories including thermal reduction, electrochemical reduction, and chemical reduction. In chemistry, a reduction is described as a chemical reaction that involves gaining electrons. The element that accepts the electrons, in this case, GO, gains electrons and minimizes the oxidation of its current state.

A thermal reduction can produce high-quality rGO, however; the high pressure associated with heating may cause structural damage to graphene layers. Chemical reduction works for commercial production but may also produce extremely toxic substances. Finally, an electrochemical reduction has proven to be the best method for consistently producing quality rGO; rGO produced using electrochemical reduction often has more conductivity than metals like silver.

GNPs

Graphene nanoplatelets (GNPs) are the final form. Nanoplatelets are synthesized in a few ways including plasma exfoliation, micromechanical cleavage, and thermal shock. Plasma exfoliation removes and decomposes contaminants, making it a preferred option for many. GNPs themselves are used for conductive inks, lubricants and as additive materials in composites.

There are many forms of graphene, but in the graphene revolution, graphene oxide (GO) and reduced graphene oxide (rGO) are the two that have excelled; that’s why we’ve spent the last two years developing our research and manufacturing capabilities around both GO and rGO. Whether or not we’ll see more forms of graphene in the future is unclear, but one thing is for sure, the next step for researchers is to make each form of graphene as pure as possible.