graphene It is a substance whose importance in technology is increasing. It is formed by hexagonal rings of carbon atoms, one of the most important and abundant elements in nature. For example, carbon is essential for life as we know it and is also the component of many minerals and many fuels (oil, coal, gases such as butane and propane, etc).
In this article we will see what graphene is, its main physicochemical characteristics and its most outstanding uses.
What is graphene?
Graphene is a substance made up of carbon atoms. carbon joined by covalent bonds forming hexagonal rings. These hexagonal rings are joined together to form a honeycomb-like layer. Each layer of hexagonal rings remains bound to another by non-covalent interactions, such as Van der Waals forces. Graphene is therefore an allotropic form of carbon, that is, a form in which carbon occurs. Other allotropic forms of carbon are graphite or diamond.
The bonds between each carbon atom in graphene form an angle of 120º and the distance between each atom is approximately 1.42 Å (ångström, 1 m = 10000000000 Å). The best bond that explains the bonds between carbon atoms in graphene is the covalent bond by hybridization of sp.two orbitals.
Each layer of hexagonal rings in graphene is approximately one carbon atom high, and this characteristic, combined with the application of highly specialized techniques, makes it possible to obtain extraordinarily thin layers of graphene. This possibility and other characteristics of graphene that we will see below make this material increasingly used in various technological fields with great expectations.
The perfect graphene would contain only hexagonal rings, although in reality pentagonal and heptagonal rings may appear, which are considered irregularities and imperfections in the structure of graphene. This structure is the basis of other graphitic substances, such as fullerenes, carbon fiber nanotubes or graphite itself. Graphite can be considered as many stacked sheets of graphene, in fact the name graphene comes from the union of graphite, a carbon mineral with a hexagonal ring structure, and ene, a root that refers to the group of alkenes (unsaturated hydrocarbons with a or more carbon-carbon double bonds). The term graphene was officially adopted in 1994, although it was discovered in the 1930s.
Among the scientists who have studied graphene are the physicists André Geim S Konstantin Novoselovambos, who developed their work mainly at the University of Manchester and were awarded the Noble Prize in Physics in 2010. Both are considered pioneers in the study of graphene and its applications in technology.
According to IUPAC (International Union of Pure and Applied Chemistry), the term graphene should be used when talking about “reactions, structural relationships or other properties of individual layers” of carbon. Bearing this in mind, it is not correct to describe graphene as “graphite layers” (graphite implies 3 dimensions while graphene implies carbon bonds in two directions), “carbon sheets” and similar concepts. So Graphene can be defined as a polycyclic aromatic hydrocarbon infinitely alternating with rings of six carbon atoms. In other words, it would be a flat molecule composed of carbon atoms that form a pattern of hexagonal rings.
Graphene’s most outstanding properties and characteristics
Graphene is a substance with some very interesting characteristics, some of them incredible. These properties, combined with the abundance of carbon in nature, have given graphene the adjective “material of the future”. Let’s look at some of the most striking features of graphene:High thermal conductivity. High electrical conductivity. High elasticity (deformable). High hardness (scratch resistance). High resistance. Graphene is approximately 200 times stronger than steel, similar to the strength of diamond, but much lighter. It’s more flexible than carbon fiber, but just as light. Ionizing radiation does not affect it. It has a low Joule effect (electron conduction heating). For the same task, graphene consumes less electricity than silicon. It is capable of generating electricity by exposure to sunlight. Graphene is a virtually transparent material. It is very dense and does not allow the passage of helium in the gaseous form, however it allows the passage of water, which, when enclosed in a graphene container, has an evaporation rate similar to that presented in an open container.
Other characteristics still under discussion are the self-cooling ability described by researchers at the University of Illinois or its self-repair ability. If a graphene layer loses some carbon atoms for whatever reason, the atoms close to the gap come together and close the gap, this self-repair capability could increase the longevity of materials made with graphene, albeit to a limited extent.
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The properties of graphene make it an ideal material for multiple applications in technology, mainly in electronics in the manufacture of integrated circuits. It is assumed that the characteristics of graphene can make it possible to build processors much faster than the current ones.
This speed has already been put to use in the manufacture of field-effect transistors built with graphene. These transistors also take advantage of the high carrier mobility with low noise that graphene features.
Among the potential applications of graphene, the following can be cited as the most interesting:Ethanol distillation at room temperature for fuel and human consumption. Ultrasensitive gas detectors optical modulators graphene transistors Faster and more efficient integrated circuits transparent electrodes electrochromic devices Solar cells Desalination antibacterial applications
The main current problem in the application of graphene is its production. Currently, investigations in the production of graphene involve the exfoliation of graphite by the transfer of graphene sheets from the graphite and epitaxial growth.
In addition to the problem of producing graphene in affordable quantities and costs for its use, there are other arguments to ensure that graphene will not replace silicon in electronic devices nor is it the technological panacea with which it is often presented. For example, graphene has no resistivity (electrical resistance) than silicon. This lack of electrical resistance means graphene can’t stop conducting electricity, which can be a big drawback.
Famous scientists in the field of technology, such as the physicist Walt De Heer, advocate the use of graphene as a new material with which things can be made that silicon cannot do, but which in no case will be a substitute, in fact De Heer states «No one who knows the world can say that seriously».
Video: Graphene and its unique properties
Below we can see a video of the Seminars Frontiers of Material Science at the Polytechnic University of Madrid, in which Francisco Guiné, from the Institute of Materials Science of Madrid, tells us about the properties and characteristics that make graphene unique and its possible and potential applications.