Graphene is attracting the attention of innovators around the world. Can this simple, lightweight, potentially inexpensive, renewable material change the world? We think so. And after you learn a bit about graphene, we think you’ll agree.
Graphene is a single layer of pure carbon atoms bonded together with sp2 bonds in a hexagonal lattice pattern. Stacked layers of graphene form graphite. Graphene, measuring one atom thick (0.345Nm), is the thinnest compound known to exist. In fact, it’s actually 2-dimensional. Before graphene was isolated, it was commonly believed that two dimensional compounds could not exist because they would be too unstable, but the carbon-to-carbon bonds in graphene are small and strong and completely stable. While it’s largely transparent, graphene, even at only one atom thick, can be seen with the naked eye.
Graphene has been studied theoretically for many years, but was first isolated in 2004 by physicists Andre Geim, Konstantin Novoselov, and other collaborators at the University of Manchester in the UK. Their initial question was: Can we make a transistor out of graphite? During their research, Geim and Novoselov extracted thin layers of graphite from a graphite crystal using Scotch tape, transferred these layers to a silicon substrate, and then attached electrodes and created a transistor. These researchers won the Nobel Prize for physics in 2010. Since this discovery, research into graphene around the world has exploded.
Everything about graphene is extraordinary.
- Thinnest. At one atom thick, it’s the thinnest material we can see.
- Lightest. One square meter of graphene weighs about 0.77 milligrams. For scale, one square meter of regular paper is 1000 times heavier than graphene and a single sheet of graphene big enough to cover a football field would weigh less than a gram.
- Strongest. Graphene is stronger than steel and Kevlar, with a tensile strength of 150,000,000 psi.
- Stretchiest. Graphene has an amazing ability to retain its initial size after strain. Graphene sheets suspended over silicone dioxide cavities had spring constants in the region of 1-5 N/m and a Young’s modulus of 0.5 TPa.
- Best Conductor of Heat. At room temperature, graphene’s heat conductivity is (4.84±0.44) × 10^3 to (5.30±0.48) × 10^3 W·m−1·K−1.
- Best Conductor of Electricity. In graphene, each carbon atom is connected to three other carbon atoms on a two-dimensional plane, which leaves one electron free for electronic conduction. Recent studies have shown electron mobility at values more than 15,000 cm2·V−1·s−1. Graphene moves electrons 10 times faster than silicon using less energy.
- Best Light Absorber. Graphene can absorb 2.3% of white light, which is remarkable because of its extreme thinness. This means that, once optical intensity reaches saturation fluence, saturable absorption takes place, which makes it possible to achieve full-band mode locking.
- Most Renewable. Statistically speaking, carbon is the fourth most abundant element in the entire universe (by mass). Because of this abundance, graphene could well be a sustainable, ecologically friendly solution for an increasingly complex world.
- Most Exceptional. What most captures the imagination is that graphene is one simple material that by itself possesses all these astonishing qualities. No other material in the world is the thinnest, strongest, lightest, and stretchiest, and can conduct heat and electricity super-fast, all at the same time.
For graphene to successfully make the leap from the lab to the marketplace, production methods need refining. As was mentioned earlier, graphene was initially isolated using Scotch tape. This method, called exfoliation, achieves single layers of graphene with multiple exfoliation steps, each producing a slice with fewer layers, repeated until only one layer, graphene, remains. Exfoliation remains the most effective way to isolate high-quality graphene in small amounts. Researchers and engineers are developing alternative methods for isolating graphene that can be used to created mass quantities. One of the most promising methods is chemical vapor deposition (CVD), or epitaxy. In very simple terms, the CVD process involves placing an often reusable thin metal substrate into a furnace heated to extremely high temperatures (900 to 1000° C). Decomposed methane gas that contains the necessary carbon and hydrogen is then introduced to the chamber, resulting in a reaction with the surface of the metal film substrate that leads to the formation of graphene. Copper, nickel, and cobalt substrates are commonly used with varying results. The chamber is then cooled rapidly to prevent multiple graphene layers from forming. While CVD graphene is promising, the results still vary widely for a number of reasons. First, the cooling conditions affect the growth behavior and quality of graphene deposits. Second, the quality of the metal substrate impacts the outcome of the graphene. And third, the quantity and quality of the reaction gasses also affects the graphene output. Precisely understanding and controlling each of these variables is critical to the success of CVD as a method for producing marketable quantities of graphene. For now, the question of how to produce large sheets of high-quality graphene efficiently and with consistent quality remains the biggest challenge facing mass-market adoption of graphene.
Challenges aside, graphene is an incredibly exciting compound with the very real potential to change the world. Initially, graphene will be used to improve the performance of existing applications, but graphene’s potential goes way beyond that. It will be used in conjunction with other emerging 2-D compounds to revolutionize the way we interact with the world.
- Electronics. Graphene conducts electricity faster than any other compound out there and is smaller and thinner as well, making it possible for all our electronics to get even smaller and faster than they are now. Graphene is also a transparent conductor, so it can replace fragile and expensive Indium-Tin-Oxide (ITO) in touch screens, light panels, and solar cells. It’s also flexible, which greatly expands the possibilities. Imagine a foldable television or windows in your home that are also projectors.
- Biological Engineering. Graphene’s large surface area, high conductivity rates, thinness, and great strength all make it perfect for a new class of fast and efficient bioelectric sensory devices for monitoring such things as DNA sequencing, glucose and hemoglobin levels, and cholesterol. Lightweight, flexible graphene-infused “rubber bands” can sense the smallest motions, such as breathing, pulse, and small movements, and make it possible to remotely monitor vulnerable patients such as premature babies. Graphene oxide also promises to revolutionize drug delivery. Studies have already explored the use of graphene oxide to deliver cancer treatments and anti-inflammatory drugs safely and precisely.
- Filtration. Graphene allows water to pass through it, but is, at the same time, almost completely impervious to liquids and gases. Because of its strength and the fineness of its pores, graphene can be used in water filtration systems, desalination systems, and biofuel manufacturing
- Mixed Materials. Graphene can be used to produce anything that needs to be strong and light. Graphene is useful for airplanes, body armor, military vehicles, and anything else that needs strength with little weight. Its electrical conductivity opens up new possibilities as well. For example, the body of an aircraft made from graphene can resist damage from lightning and also communicate electronically any problems with the structure to the pilots. Concrete and other materials are also being developed that take advantage of the many exceptional properties of graphene.
- Batteries. Batteries that use graphene to store energy rather than traditional lithium ion will be stronger, more stable and efficient, and will last longer. Electric cars, laptops, and other devices can be more durable, light weight, and efficient with graphene-enhanced batteries.
Graphene is a powerful, versatile material. The isolation of this one amazing material has blown the possibilities of what we can achieve wide open. Previous limitations are gone and a whole universe of applications lie in front of us just waiting to be discovered.