Graphene, Overhyped or Truly a Wonder Material?
After researching graphene, one should be excused for thinking that the worlds’ scientists should just bite the bullet, coat a monkey in this stuff and shoot it into space. The world needs a real live Silver Surfer, doesn’t it? According to all the hype, graphene might be the substance we need to achieve this. But seriously, after a little research this stuff does seem as amazing as everyone is making it out to be. This article attempts to explain what graphene is in layman’s terms. Future graphene related posts will outline some of the more interesting uses that people are researching for the material and a breakdown of the various methods for creation of the material to date (some of which you may be able to pursue in your basement or hackerspace).
What is graphene– Graphene is basically a really, really, really thin sheet of graphite. That’s right, it’s really just that simple. It turns out that when you peel a single atom’s thickness of graphite off, it forms an incredibly amazing two dimensional material (one atom thickness isn’t really a thickness, it’s more like a binary state of existence). The bonded carbon atoms of the graphite form a sheet (usually a really tiny sheet) which is one of the challenges of graphene technology. Depending on what is done to the sheet of graphene scientists can exploit its various properties. While it was first officially discovered in 2004 by Andre Geim and Konstantin Novoselov at Manchester University, scientists have been theorizing graphene’s existence since Benjamin Brodie started pondering the properties of reduced graphite in 1859. Philip Russel Wallace was among the first to truly start documenting the concept in 1947 as part of his exploration into the electronic properties of 3-D graphite atoms. While theories and research on graphene date back to the 19th century, no one had reliably produced a sample thinner than fifty layers before 2004.
What exactly are the properties of graphene that makes it so interesting?
It’s incredibly conductive– To start with, graphene conducts electricity better than silicon, the material technologists currently use to create transistors and IC chips. “Graphene has an electron mobility 200000 cm2/Vs, almost 200 times higher than silicon.” In fact, graphene is so conductive that scientists have been concerned that there is no way to “turn off” it’s conductivity, something that is crucial for transistor usage. Luckily the material has a property called “negative resistance” which means that when a larger amount of voltage is applied to graphene it has a momentary drop in voltage, a counterintuitive concept, but one that researchers are hoping to exploit in a similar manner to the band gap properties of current transistors. Most of graphene’s superconductive properties also apply to heat.
Unsurpassed strength– It’s really, really strong despite it’s perfect two dimensional film state. Researchers at Columbia University claim that a perfect graphene film is the strongest material known to man.
It’s two dimensional, literally– It’s one of the first two-dimensional materials ever discovered by humans. This means you can fit graphene into incredibly tight spaces, such as DNA. It also means that when it gets integrated into technologies such as touchscreens it will take up less space, making for thinner displays. The two-dimensional property also allows technologists to use it as a building block for nanotechnology development.
It can be used as a filter at the atomic level– A defect free sheet of graphene is water permeable, but will not allow any other material through. Sir Andre Geim discovered this by covering the top of a bottle of vodka with the substance. Despite the graphene barrier the vodka gained potency as the water in it evaporated. Strangely enough Geim reports that graphene won’t allow any other substances, such as helium or any other gasses or liquids through but water passes as if the graphene film is not even present. That’s a pretty useful property considering the strange and sometimes toxic things humans have been doing to water recently. Researchers have also been experimenting with punching nano sized holes in the film to selectively filter other liquids and gasses through the material.
It self heals– Defects in graphene films, as well as impurities, have been shown to “self heal” as the carbon atoms realign during an annealing process. (Hit it with the right amount of heat and the cracks in the structure go away.) I’m not entirely sure about this process since people seem to be annealing in different environments, such as vacuums or gaseous atmospheres, to achieve different effects. Admittedly this process tends to leave it bonded to whatever substrate material it is on, but that’s a different egg to crack.
It’s biodegradable– Ok. This one is a double edged sword. Sure it’s biodegradable, but the nano-particles of this substance are really transportable by water. Combine that property with the possibility of being toxic to humans and widespread usage of this stuff could spell out some serious trouble for people despite the material being biodegradable.
It’s transparent– Meaning we could use it in display screens, solar cells, fiber optics, laser, windows, radiation detectors, bio-medical devices, cameras and even fishbowls. Ok, not fishbowls since the water would leak right through, but you get the point. Researchers have even used graphene to enhance low-light camera performance.
It’s cheap– At least when compared to other substances, such as indium tin oxide, that are currently used to manufacture touch screens. The extraction, or reduction process isn’t currently inexpensive, but that could change any day as more ways to create graphene are discovered. (More on this in later posts.)
It’s super lubricious– That’s not a typo. In non-vacuum environments graphene surfaces move incredibly smoothly when in contact with each other. This is a property called superlubricity and occurs because of the unique way that the atoms fit together, allowing for the structures to travel through the uniform paths of each others carbon atoms. Graphene slip and slide for our Silver Surfer friend, anyone?
It’s diamagnetic and can be magnetic– Simply described, put it over a magnet and it floats in the air. That’s right, it floats. It’s similar to placing two magnets close to each other in an orientation that makes them repel each other. Except graphene has no magnetic field, so it always floats regardless of it’s orientation. Give our Silver Surfer a thin magnet to sit on and that graphene slip and slide just got even faster! Strangely enough researchers at IMDEA-Nanociencia Institute and from Autonoma and Complutense Universities of Madrid have discovered that if one forms a cylinder with graphene it even becomes magnetic.
It’s super low density– This makes it an ideal material for mixing with other materials with the intention of creating things like aerospace technology, windmill blades, cars, anything that needs to be buoyant and athletic gear for starters. It’s so light that people have demonstrated balancing samples of graphene based aerogels on top of things like flower stamen, blades of grass and feathers. These graphene aerogel materials can also be physically compressed and upon release they spring back to their original structure. This might be ideal for application in all sorts of safety equipment. Personally, I want some in the soles of my snowboard boots.
Ability to attach a wide variety of molecules to it’s carbon atoms– This makes it the perfect material to combine with a wide variety of technologies. Examples of this include carbon nano-tubes and DNA.
When combined with ionic fluids it can be used to generate electricity– People have known for years that movement of ionic liquids creates electricity. Unfortunately it usually requires large amounts of pressure and channeling through holes or tunnels. With graphene there’s no need for any pressure or containment other than gravity to create this energy. Researchers in China have shown that droplets of seawater on a graphene surface create a small electrical potential dependent on the amount of ionic fluid and it’s velocity. This effectively creates a sort of capacitor where the saltwater meets the graphene with a positive charge at the front in comparison to the rear end of the droplet. I can’t wait until my raincoat charges my cell phone, personally.
Wow. Just listing the properties of graphene took longer than I expected. I’d say this material does indeed warrant all of the attention it’s been getting from the scientific community. Feel free to let me know in the comments if you find any errors or you have more information. Stay tuned for a compiled list of applications and various ways that people are making graphene in labs and at home.
References- graphene.manchester.ac.uk, graphene-battery.net, researchgate.net, pveducation.org, sciencemag.org, pubs.acs.org, ncbi.nlm.nih.gov, techconnectworld.com, nature.com, sciencedirect.com, engineering.stanford.edu, ejournal.unam.mx