Graphene - What Is It?
Written By Jesus de La Fuente
In simple terms, graphene, is a thin layer of pure carbon; it is a single, tightly packed layer of carbon atoms that are bonded together in a hexagonal honeycomb lattice. In more complex terms, it is an allotrope of carbon in the structure of a plane of sp2 bonded atoms with a molecule bond length of 0.142 nanometres. Layers of graphene stacked on top of each other form graphite, with an interplanar spacing of 0.335 nanometres.
It is the thinnest compound known to man at one atom thick, the lightest material known (with 1 square meter coming in at around 0.77 milligrams), the strongest compound discovered (between 100-300 times stronger than steel and with a tensile stiffness of 150,000,000 psi), the best conductor of heat at room temperature (at (4.84±0.44) × 10^3 to (5.30±0.48) × 10^3 W·m−1·K−1) and also the best conductor of electricity known (studies have shown electron mobility at values of more than 15,000 cm2·V−1·s−1). Other notable properties of graphene are its unique levels of light absorption at πα ≈ 2.3% of white light, and its potential suitability for use in spin transport.
Bearing this in mind, you might be surprised to know that carbon is the second most abundant mass within the human body and the fourth most abundant element in the universe (by mass), after hydrogen, helium and oxygen. This makes carbon the chemical basis for all known life on earth, so therefore graphene could well be an ecologically friendly, sustainable solution for an almost limitless number of applications. Since the discovery (or more accurately, the mechanical obtainment) of graphene, advancements within different scientific disciplines have exploded, with huge gains being made particularly in electronics and biotechnology already.
Graphene productions challenges
The problem that prevented graphene from initially being available for developmental research in commercial uses was that the creation of high quality graphene was a very expensive and complex process (of chemical vapour disposition) that involved the use of toxic chemicals to grow graphene as a monolayer by exposing Platinum, Nickel or Titanium Carbide to ethylene or benzene at high temperatures. Also, it was previously impossible to grow graphene layers on a large scale using crystalline epitaxy on anything other than a metallic substrate. This severely limited its use in electronics as it was difficult, at that time, to separate graphene layers from its metallic substrate without damaging the graphene.
However, studies in 2012 found that by analysing graphene’s interfacial adhesive energy, it is possible to effectually separate graphene from the metallic board on which it is grown, whilst also being able to reuse the board for future applications theoretically an infinite number of times, therefore reducing the toxic waste previously created by this process. Furthermore, the quality of the graphene that was separated by using this method was sufficiently high enough to create molecular electronic devices successfully.
While this research is very highly regarded, the quality of the graphene produced will still be the limiting factor in technological applications. Once graphene can be produced on very thin pieces of metal or other arbitrary surfaces (of tens of nanometres thick) using chemical vapour disposition at low temperatures and then separated in a way that can control such impurities as ripples, doping levels and domain size whilst also controlling the number and relative crystallographic orientation of the graphene layers, then we will start to see graphene become more widely utilized as production techniques become more simplified and cost-effective.
Being able to create supercapacitors out of graphene will possibly be the largest step in electronic engineering in a very long time. While the development of electronic components has been progressing at a very high rate over the last 20 years, power storage solutions such as batteries and capacitors have been the primary limiting factor due to size, power capacity and efficiency (most types of batteries are very inefficient, and capacitors are even less so). For example, with the development of currently available lithium-ion batteries, it is difficult to create a balance between energy density and power density; in this situation, it is essentially about compromising one for the other.
In initial tests carried out, laser-scribed graphene (LSG) supercapacitors (with graphene being the most electronically conductive material known, at 1738 siemens per meter (compared to 100 SI/m for activated carbon)), were shown to offer power density comparable to that of high-power lithium-ion batteries that are in use today. Not only that, but also LSG supercapacitors are highly flexible, light, quick to charge, thin and as previously mentioned, comparably very inexpensive to produce.
"The possibilities of what we can archive with the materials and knowledge we have, have been blown wide open"
Graphene is also being used to boost not only the capacity and charge rate of batteries but also the longevity. Currently, while such materials as silicone are able to store large amounts of energy, that potential amount diminishes drastically on every charge or recharge. With graphene tin oxide being used as an anode in lithium ion batteries for example, batteries can be made to last much longer between charges (potential capacity has increased by a factor of 10), and with almost no reduction in storage capacity between charges, effectively making technology such as electronically powered vehicles a much more viable transport solution in the future. This means that batteries (or capacitors) can be developed to last much longer and at higher capacities than previously realised. Also, it means that electronic devices may be able to be charged within seconds, rather than minute or hours and have hugely improved longevity.
Consumers can already purchase graphene-enhanced products to use at home. One company already produces and offers on the market conductive ink (first developed by researchers at the University of Cambridge in 2011). This is made by effectively mixing tiny graphene flakes with ink, enabling you to print electrodes directly onto paper. While this was previously possible by using organic semiconductive ink, the use of graphene flakes makes the printed material vastly more conductive and therefore more efficient.
Another use for graphene along similar lines to those mentioned previously is that in paint. Graphene is highly inert and so can act as a corrosion barrier between oxygen and water diffusion. This could mean that future vehicles could be made to be corrosion resistant as graphene can be made to be grown onto any metal surface (given the right conditions). Due to its strength, graphene is also currently being developed as a potential replacement for Kevlar in protective clothing, and will eventually be seen in vehicle manufacture and possibly even used as a building material.
As graphene has been proven to be much more efficient at conducting electrons than silicon, and is also able to transfer electrons at much faster speeds (relatively speaking, 1000 kilometres per second, 30 times faster than silicon), in the next few years you will begin to see products from consumer electronics companies, such as Samsung (who have been pouring money into researching the uses of graphene in telecommunications and electronics and have already taken out a huge number of patents concerned with the uses and manufacture of graphene in electronic devices) based on flexible, robust, touchscreen devices such as mobile smartphones and wrist watches.
(Die size 10 mm x 10 mm)
For Sensing applications
Highly Concentrated Graphene Oxide (2.5 wt% Concentration)
Easy Transfer: Monolayer Graphene on Polymer Film
(1 cm x 1 cm)
This could mean foldable televisions and telephones and eventually electronic flexible newspapers containing all of the publications you are interested in that can be updated via wireless data transfer. Being extremely translucent, in the coming years you can also expect to be able to fit intelligent (and extremely robust) windows to your home, with (potentially) virtual curtains or displaying projected images of your choice.
Combining a few of these aforementioned potential uses, can you imagine car security systems that are connected to the paint on your vehicle? Not only would your car alarm be able to tell you if someone is touching your vehicle, it would be able to record that information and send it to you via your smartphone in real-time. It could also be used to analyse vehicle accidents to determine initial contact patches and resultant consequential energy dispersion.
Soon we will begin to see clothing containing graphene-enhanced photovoltaic cells and supercapacitors, meaning that we will be able to charge our mobile telephones and tablet computers in a matter of minutes (potentially even seconds) whilst walking to school or work. We may possibly even see security-orientated clothing offering protection against unwanted contact with the use of electrical discharge.
What all this means is that this discovery, made by a physics professor and his PhD student in a laboratory in Manchester, using a piece of graphite and some Scotch tape has completely revolutionised the way we look at potential limits of our abilities as scientists, engineers and inventors. The possibilities of what we can achieve with the materials and knowledge we have, have been blown wide open, and it is now conceivable to imagine such amazing prospective situations as lightning fast, yet super-small computers, invisibility cloaks, smart phones that last weeks between charges, and computers that we can fold up and carry in our pockets wherever we go.
Jesús de la Fuente
Jesús de la Fuente
Jesús de la Fuente
Jesús de la Fuente
Jesús de la Fuente
Jesús de la Fuente
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