Graphene: everybody's talking about it.
When hearing some of its basic properties, you might have wondered if people were confusing
it with some kind of substance only found in comic books.
It's one atom thick, conducts electricity better than silver, conducts heat better than
diamond, and it's stronger than steel.
It would take the focused force of an elephant balancing on a pencil point to pierce through
a piece of graphene as thick as plastic wrap.
And yet, graphITE is made of the same stuff.
And yeah, that crumbly stuff used to make your pencil is a lot less impressive.
So what's up?
Graphene is made of carbon, and carbon has only two naturally occurring crystalline structures;
graphite, which is just stacks and stacks of graphene piled on top of each other, and
diamond, which is a network of carbon atoms arranged into tetrahedrons one after the other.
For being composed of entirely the same element, those two things don't seem to have a lot
in common.
Diamond is clear, graphite is black.
Diamond is a nearly-perfect electrical insulator, while graphite is both a great conductor of
heat and electricity.
The differences between these substances all come down to the arrangement of their atoms.
Carbon has four outer electrons.
In diamond, all four of those electrons bond to carbon atoms around it, forming those tetrahedrons.
This makes for an extremely rigid and strong crystal.
It's an insulator, because there are no electrons left over to carry a current, and it's clear
because light can't easily excite electrons that are tied up in such stable bonds, which
is where they'd otherwise be absorbed.
Graphite, on the other hand, is a crystalline form of carbon in which each atom is only
bonded to three other carbon atoms.
Those atoms form a two-dimensional sheet of hexagons in which each atom has one unpaired
electron left over.
And those electrons will go flying across the matrix of atoms if you apply an electric
current, allowing it to readily conduct electricity.
They also gobble up any photons coming their way, which is why graphite is black.
But while graphite is a great conductor, its natural form consists of layers of those sheets.
So if a current is applied to it, those free electrons have lots of different directions
they can go in, taking tangents up and down and left and right and so on.
But if you strip away just a single layer, forming graphene, then you have what amounts
to an electron super highway, a flat matrix of carbon atoms for that current to fly across.
And those sheets of carbon are pretty easy to separate because they're not molecularly
bonded to each other.
That's why graphite is so soft.
Instead, they're held together by Van Der Waal's bonds, kind of a weak, electrostatic
bond that's the same force that makes sticky tape sticky.
And in fact, graphene was only discovered in 2004 when two physicists at the University
of Manchester, Andre Geim and Konstantin Novoselov, decided to use sticky tape to peel off thinner
and thinner layers from a slab of graphite.
Eventually, they got a layer just one atom thick.
So that's what it is, but what is it good for?
Because of its terrific conductive properties, scientists are excited by the possibility
of using graphene as the replacement for silicon in microchips.
Not only can electrons move faster across graphene, they're also subjected to less noise.
That means the electron can move from one side of the sheet to the other in a straight
line without detouring around a whole lot of atomic potholes.
Scientists think that graphene transistors could operate at frequencies of up to a thousand
gigahertz.
That's ten times the maximum of silicon.
Another proposed use of graphene is in touch screens.
The topmost layer of a touchscreen has to be an excellent conductor of electricity,
so the device can sense your fingertip.
The material we use now is indium tin oxide, but it's both rare and brittle.
Even ground into powder, graphene retains many of it's extraordinary properties, so
it could replace graphite or other forms of carbon in anything from car tires to double-A
batteries to make them stronger or more conductive.
The biggest problem with graphene though is how hard it is to make.
I mean, peeing off a tiny sheet at a time with sticky tape isn't really scaleable.
We can grow graphene sheets by hitting up a sheet of hydrocarbons like methane until
the hydrogen separates, leaving only the carbon behind, but the graphene we get from this
is mostly low quality.
Basically, it's hard to create a one atom thick sheet of anything.
And it's also really hard to get a completely pure sample of anything, and here we're trying
to do both.
But then again, the silicon industry faced the same purity problem fifty years ago, and
we eventually solved that problem with time and some money.
So in some more time, and some more money, I'm sure we'll do the same thing for graphene.
Thanks for watching this SciShow dose.
If you'd like to help us keep exploring the frontiers of awesomeness, go to subbable.com/scishow
to find out how you can become a supporter.
And if you wanna keep getting smarter with us, don't forget to go to youtube.com/scishow
and subscribe.