Graphene and its derivatives

GRAPHENE AND ITS DERIVATIVES

What is graphene?

Graphene is a nanomaterial constituted by a single-atom-thick sheet of carbon in which the carbon atoms are tightly arranged in a characteristic hexagonal structure.

Estructura grafénica

Carbon atoms joined by covalent bonds forming a graphene sheet.

Properties of graphene

Graphene is a material with unique properties that make it especially attractive, from both the point of view of research and the applications of its derivatives:

  1. Electronic properties. Graphene is the material with the highest electrical conductivity known. Thus, its intrinsic resistivity value beats the marks of silver, which was the material with the lowest resistivity.
  2. Physicochemical properties. The 0.34 nm of the thin carbon sheet that makes up graphene the thinnest material known.
  3. Thermal properties. The thermal conductivity of graphene, or what is the same, the ability of a material to transfer heat, is the highest of any material known to date.
  4. Optical properties. Being a material with such reduced thickness, photons easily pass through it, causing a graphene sheet to only absorb 2.3% of the intensity of the light that reaches the surface.

Applications of graphene: is it accurate to say it?

Graphene and its extraordinary properties have no final application beyond the laboratory. Therefore, it is more correct to speak of carbon nanomaterials or graphene derivatives when we refer to its industrial applications.

Some of the most important carbon nanomaterials are nanofibers, nanotubes, nanospheres or fullerenes; and within this group, graphene derivatives such as graphene oxide (GO) and reduced graphene oxide (rGO) stand out.

Nanometric comparison of different carbonaceous materials (Calandra et al., 2020).

Graphene derivatives: differences and applications

Graphene can stick together in layers that interact weakly. Thus, we can differentiate monolayer, bilayer, few-layer (3 to 4) or multilayer (5 to 10) graphene structures. When this graphene is grouped in an indefinite number of layers, a material known as graphite is obtained, from which graphite oxide can be generated and, in turn, other graphene derivatives: graphene oxide and reduced graphene oxide. Due to their size, these can be considered nanomaterials.

  1. Graphene oxide (GO). Graphene derivative achieved through a process called exfoliation (shaking or sonication).
  2. Reduced graphene oxide (rGO). Graphene derivative produced by removing the oxygen content from the graphene oxide structure through chemical or thermal processes.

Representation of one of the methods of obtaining graphene oxide and reduced graphene oxide.

The main difference between these graphene derivatives lies essentially in chemical aspects, such as the level of oxygen: while the content of oxygen in graphene oxide ranges from 40 to 50% by weight, in the reduced graphene oxide that content is circa 40%.

The most remarkable applications of graphene oxide are:

  1. Composites, due to their easy dispersibility in water and organic solvents because of the presence of oxygenated groups.
  2. Desalination and purification of water, due to its ease of integration within both reverse osmosis membranes and conventional ones.
  3. Energy storage in supercapacitors, improving electrical conductivity and specific capacitance.
  4. Biocidal devices, due to their proven antibacterial properties these nanomaterials can be used in the manufacture of bandages, food packaging and medical products.
  5. Electrochemical immunosensors, glucose sensors and DNA and protein detectors, as in the diagnosis of diseases such as HIV.

For its part, the main applications of reduced graphene oxide are:

  1. Anodes for high performance batteries.
  2. Aptasensors, or sensors to detect cancer cells.

Thus, we see how the applications of graphene derivatives in different industries are numerous. At Phi4tech and its subsidaries, we have used nanomaterials based on graphene derivatives to create the only paint in the world that combines lime and graphene technology. In addition, we have designed more efficient and sustainable batteries and supercapacitors, medical polymers with antibacterial properties and industrial polymers with special properties.