Applications of graphene

10 August 2015

Interview with

Andrea Ferrari, University of Cambridge

What is graphene actually doing for us right now? Andrea Ferrari leads the CambridgeWarning symbol for laser beam Graphene Centre, which has been set up to investigate the science and technological applications of graphene. Andrea is working on a range of projects that are already delivering promising results. He started by explaining to Chris Smith, some "concrete" findings...

Andrea - Cambridge Graphene Centre works with a variety of companies, almost 40 at the moment. And one of these companies is called Italcementi. It's one of the biggest concrete producers in the world and within the so called graphene flagship project which is a 1 billion Euros project that will try to bring graphene to the factory floor within the next 10 years. We are trying to help them, together with the University of Bologna to develop a new kind of concrete that will be self-cleaning but especially, will reduce pollution. And to do so, graphene is added to the surface of concrete. The concrete has also other nanoparticles inside and helps trap gasses that could be potentially toxic - such as NOx's.

Chris - We can already get surfaces to clean themselves up though, can't we? Famous structures such as king's cross station in London has self-cleaning glass where light hits the glass, it drives a chemical reaction that burns off the dirt effectively. Are you sort of doing the same thing here then?

Andrea - Yes, indeed. In terms of self-cleaning concrete, this company has already a brand out that you can purchase. What happens is that if you put graphene in it, you can potentially double the efficiency of the process.

Chris - That's a massive difference!

Andrea - Yeah. A huge difference, and graphene is enhancing the properties of the nanoparticles that are already present there.

Chris - Right. So, on the surface of the concrete are some nanoparticles. But in glass, they use titanium dioxide. Is that the same in concrete?

Andrea - Indeed. It's titanium dioxide and what the key finding is if you put together titanium dioxide and graphene, you enhance the process by a factor of two or even more.

Chris - Do we know how that works?

Andrea - That is the sticking point. We don't know exactly how it works and that's why we are trying to help. We are trying to conduct some basic physics investigation in order to figure out exactly the process that is underneath this fantastic property.

Chris - Would you have to pour concreate which has got graphene right the way through? So, that's going to be an enormous amount of graphene when you think how much concrete get made every year, or is this like a veneer. You smear this on the surface of a concrete and you then get the cleaning just on the surface. 

Andrea - It is a surface effect, so we are speaking about if a relatively thick layer at the surface of the concrete. So, not the entire concrete will be full of this material. But even this will require significant production of graphene.

Chris - And will it work indefinitely?

Andrea - At the moment, there are no long-term studies. But we do know that graphene is really resilient, so there's no reason why they should stop after many years.

Chris - Goodness! And what sorts of applications might there be - just buildings in cities or could it be used in other places as well?

Andrea - Another interesting application is in tunnels where you have to have cars going through. As you know at the moment you have some ventilation systems, but having a concrete that is able to reduce pollution will be much safer and in the case of a fault of the ventilation system, the concrete will still be able to reduce the pollution in the gallery. So, that's a very interesting application as well.

Chris - Is it not dark in a tunnel though?

Andrea - It is dark but the light that you use is not visible light so we can still work under these conditions.

Chris - Could you retrofit this to existing buildings? I'm thinking that there are lots and lots of buildings built in concrete in big cities all around the world. They're all getting dirty. There's lots of pollution around. Could we veneer buildings with this after they've been built or does it need to be part of the fabrication?

Andrea - I think in principle, you can do that, but of course I'm not a builder. So, you probably have to ask one of them.

Chris - What about other aspects of graphene interacting with lights? Because one of the other claims that's being made is that it's extremely good, potentially, in the world of lasers. Why is that?

Andrea - Yes, indeed. We heard before from James that graphene is very transparent but actually it's also the most absorbing material for the thickness it has. Because the thickness of graphene is one-billionth of a metre, so when we speak about 2% of a one-billionth of a metre, it's a huge number. So, graphene can help create extremely fast Lasers.

Chris - Define an extremely fast Laser. What does that mean?

Andrea - We are speaking of the order of one-millionth of a billionth of a second of a pulse, which is really record property.

Chris - Why is that useful? Why do I want a laser that just sends me the briefest of all brief flashes?

Andrea - For example, to send data to. In the future we want to exchange information, streaming high-definition movies in a few seconds and that's optical telecommunications, are one of the options. So, it's certain you want to have extremely fast pulses. Another application is for surgery, because in this way you can ablate material. For example, if you think about laser surgery without cooking the surface of the skin.

Chris - Useful.

Andrea - That would be quite useful as well.

Chris - How does the graphene do that then? How would one incorporate graphene into a laser to achieve that effect?

Andrea - Graphene works like a sponge for water. So, if you think about water flowing and you put a sponge under the water. The sponge will fill with water, and momentarily the water will not flow underneath the sponge. Then you squeeze the sponge, the water will keep going until it gets filled up again. So, graphene does exactly the same with light. Momentarily it can absorb all the light by hanging on to it.

Chris - Any colour? Any Wavelength?

Andrea - Any wavelength. It's the only material that will work at absolutely every wavelength of light.

Chris - And that's why it looks so black when you put lots of it together to make graphene, isn't it?

Andrea - Indeed. Because it's 2% per layer, so if you have 20 or 40 layers, then it's completely black. But if do so, you don't have a laser. So, you still have to use them...

Chris - And how do you give it the metaphorical squeeze of the sponge then, to get the light out. How do you do that?

Andrea - The good thing is that the graphene does it by itself. So, it's one property that is intrinsic to the graphene. You don't need to squeeze it. The excited states in graphene go to the ground state, and that's the squeezing, extremely fast of order of a millionth of a second. Millionth of billionths of a seconds by themselves. So, you don't need to squeeze it. It does it for you.

Chris - Therefore, the application would be you make some kind of graphene filter that you put in front of or within your laser. And you then fire the laser light into it, and it then does or takes care of the creation of the pulses.

Andrea - Yeah. If you think, for example, of a simple laser pointer, if you put graphene on the front of it, then you will get laser pulses out of it.

Chris - What about the electrical properties of graphene? Because one of the other things that people are very excited about is it is, as James was saying, very conductive and, therefore, might be able to make a big difference to data transmission and the way computers work. I know my computer, my mobile phone gets very, very hot when I'm doing even the most mundane thing with it.

Andrea - Yes. This is linked to what we said before. Graphene has an exceptional interaction with light. And so, in order to transmit data, even the laser we already discussed, you need then what is called a modulator in order to give, like what we are doing now, we go on air so we need to put the message in. And then we need the detector, which is like an antenna, the receiving end. Graphene can do the three parts that we discussed but the consumption of energy that is ten or even one hundred times smaller what silicon is doing at the moment.

Chris - So, that should save the cellphone battery for a little bit longer, shouldn't it?

Andrea - Yes, indeed. It should also not cook your pants when you have the cellphone on.

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