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The structure of graphene is comprised of a single thin layered sheet of tightly packed carbon atoms arranged in the vertices of a hexagonal lattice resembling honey comb.
Graphite, on the other hand, is made up of several layers of graphene stacked on top of each other with an inter-planar distance of 0.335 nm between the subsequent layers1. Graphene is the thinnest single atom-thick material known to man, it is extremely lightweight weighing only 0.77 mg per square meter. Despite its light weight, graphene is 100 – 300 times stronger than steel with a tensile stiffness of 150,000,000 psi1.
The sp2 hybridization of s, px and py orbitals allows for the formation of s bonds with bond lengths of 1.42 A° between the neighboring carbon atoms in the two-dimensional plane, while the electron in the pz orbital makes the p bond, which sticks out of the plane2.
The electrons present in graphene are capable of traveling at a great velocity, allowing for this material to be considered the best conductor with its electron mobility measuring at 15000 cm2/V/s. The p- band and p* bands formed by the hybridization of p bonds are responsible for these special electronic properties2. Due to the unique levels of visible light absorption of graphene, it has the potential to be used in spin transport.
It is graphene’s exceptional electrical, mechanical, optical and thermal properties, as well as its eco-friendly nature, that have made it an area of intense research in the fields of electrical, electronics and material sciences. As impressive as it sounds, graphene is not yet commercially used due to the difficulties in the preparation of high quality graphene on a large scale in a cost-effective manner.
For example, the laboratory preparation of graphene using chemical vapor disposition method involves many toxic chemicals, while also requiring ethylene or benzene to be exposed to platinum, nickel or titanium carbide to grow graphene as a single layer1.
Other methods involve cooking graphite at a precise temperature with chemicals such as sulfuric acid, sodium nitrate, potassium permanganate or hydrazine for long periods of time4. All these methods to prepare graphene are energy intensive and potentially hazardous, yet can only yield very low amounts of graphene5.
Researchers at Kansas State University’s Department of Physics recently discovered and patented a viable process to mass produce graphene using just three ingredients: hydrocarbon gas, oxygen and spark plug. Christopher Sorensen’s team discovered graphene serendipitously while they were attempting to develop carbon soot aerosol gels by filling a 17 liter aluminum chamber with acetylene and oxygen and detonated the chamber with a spark plug3.
The resulting soot appeared to be what the team described as a black angel food cake, which was later discovered to be graphene in actuality. Using this method, Sorensen’s team prepared graphene in quantities of grams, unlike the other methods where only milligram quantities have been capable of being recovered3.
This group of Researchers is now trying to improve the quality of graphene produced by their detonation process, as well as potentially scaling up the laboratory process to industrial level3. They believe that recovering graphene soon after the detonation process is completed would yield them a better-quality graphene than the graphene collected a few minutes after detonation3. Sorenson’s team is therefore attempting to upgrade their equipment in order to allow for a faster recovery period.
If Sorensen’s method could be successfully scaled up to the industrial level to produce high quality graphene in large amounts, graphene will soon be used in a wide variety of applications that will utilize its great mechanical strength, inordinate ability to conduct thermal and electrical energies, as well as its unusual levels of light absorption. Some of such applications could include light emitting diodes, supercapacitors, batteries, transparent conductive films, catalytic systems, smart windows, touch panels, wearable devices and many more1, 2, 3.
References and Further Reading
- "Graphene - What Is It?" Graphenea. Web. https://www.graphenea.com/pages/graphene#.WKYtFhiZPdQ.
- Cooper, Daniel R.; D’Anjou, Benjamin; Ghattamaneni, Nageswara; Harack, Benjamin; Hilke, Michael; Horth, Alexandre; Majlis, Norberto; Massicotte, Mathieu; Vandsburger, Leron; Whiteway, Eric; Yu, Victor (3 November 2011). "Experimental Review of Graphene" (PDF). ISRN Condensed Matter Physics. International Scholarly Research Network. 2012: 1–56.
- "Kansas State University." Physicists Patent Detonation Technique to Mass-produce Graphene | Kansas State University | News and Communications Services. Web. http://www.k-state.edu/media/newsreleases/2017-01/graphenepatent12517.html.
- "Physicists Patent Detonation Technique to Mass-produce Graphene." Phys.org. Web. https://phys.org/news/2017-01-physicists-patent-detonation-technique-mass-produce.html.
- "A Simple Way To Mass-Produce Graphene With Just Three Ingredients Discovered." Science World Report. 26 Jan. 2017. Web. http://www.scienceworldreport.com/articles/56535/20170126/simple-way-mass-produce-graphene-three-ingredients-discovered.htm.