Oxford and Dublin boffins have unlocked a doorway leading to more than 150 super-thin exotic nanosheet materials just one atom thick.
The names sound like a chemist's molecular roll call: boron nitride (BN), molybdenum disulphide (MoS2), and bismuth telluride (Bi2Te3). None of these compounds are new – but single-atom-thick* crystals or flakes made of of these compounds would be. Freed from characteristics caused as a result of them being in instantiations multiple atoms thick, they can – among other things – become vastly better thermoelectric devices, generating electricity from heat.
The research was carried out by a team of boffins led by CRANN (Center for Research on Adaptive Nanostructures and Nanodevices), Dublin's Trinity College and the University of Oxford. What this team has done, following the example set by Russian Nobel Prize-winning boffins last year with graphene, a similarly two-dimensional material – if you regard single-atom thickness as being equivalent to having no thickness dimension. Individual flakes of graphene have electronic and mechanical properties that are very different from its parent crystal material, graphite.
Graphite is a layered crystal material and, apparently, there are more than 150 of these materials which could be used, in theory, to create single-atom-thick flakes that can be metallic, insulating or semi-conducting according to their chemical composition and atomic arrangement. They could be used as super-capacitators, providing energy thousands of times faster than batteries; reinforcing components to plastics to add strength; or as thermoelectric devices, providing electricity from heat. This latter application has a green aspect: waste heat from industrial and other processes could be used to generate electricity and so recycle the otherwise lost heat energy.
The Trinity College release quotes Professor Jonathan Coleman of its School of Physics, also Principle Investigator at CRANN. He said: "In gas-fired power plants, approximately 50 per cent of energy produced is lost as waste heat, while for coal and oil plants the figure is up to 70 per cent ... the development of efficient thermoelectric devices would allow some of this waste heat to be recycled cheaply and easily, something that has been beyond us, up until now."
The boffinry here is in crafting the nanosheets by applying ultrasound to parent crystals and dissolving the exfoliated bits in common or garden industrial solvents. Existing methods are labourious, low-yield and take a long time. The new way of crafting nanosheets has high yields, is low-cost, and offers a lot of throughput. Dr Valeria Nicolosi, of the Department of Materials at the University of Oxford, said: "Within a couple of hours, and with just 1mg of material, billions and billions of one-atom-thick nanosheets can be made at the same time from a wide variety of exotic layered materials."
You could use the stuff by depositing nanosheets of crystals or film on a base layer to create a device with properties that you want, once you understand which properties are associated with which nanosheet material. The research is all on its potential for now, but the boffins have 150 or so nanosheet material possibilities to play with. There are more details in a paper published by the Science journal (abstract), but you'll need a subscription or pay a read fee to get at it. Where's WikiLeaks when you need it? ®
The Science journal abstract says: "Electron microscopy strongly suggests that the material is exfoliated into individual layers." In other words the boffins don't know for sure.