The reason, it turns out, is that the material is so thin that the way it reacts is strongly affected by the electrical fields of atoms in the material beneath it. This means that it is possible to create devices with a micropatterned substrate – made up of some silicon dioxide regions and some coated with boron nitride – covered with a layer of graphene whose chemical behaviour will then vary according to the hidden patterning. This could enable, for example, the production of microarrays of sensors to detect trace biological or chemical materials.
Another week, and in our slow high summer season, some surprising graphene news from the scientists at America’s MIT. Graphene’s properties alter with the material it’s wrapped around. With untypical American understatement, the MIT news office writes “this could enable, for example, the production of microarrays of sensors to detect trace biological or chemical materials.” It will do a whole lot more than that. But I am not a scientist, so I’ll quote for the MIT press release:
“James Tour, a professor of chemistry and of computer science at Rice University who was not involved in this research, says, ''This is the first systematic study of the substrate's effect on graphene's chemical reactivity. This is a very carefully conducted study with convincing results. I predict that it will become a frequently cited publication.''”
Below this morning’s news from MIT. I had been beginning to think that all our northern hemisphere boffins had gone on holiday, with the southern hemisphere’s junketing at the summer London Olympics. This just might be MIT’s biggest contribution to our arriving graphene/graphite age.
Graphene's behaviour depends on where it sits news
By David L. Chandler, MIT News Office 14 August 2012
When you look at a gift-wrapped present, the basic properties of the wrapping paper – say, its colours and texture – are not generally changed by the nature of the gift inside.
But surprising new experiments conducted at MIT show that a one-atom-thick material called graphene, a form of pure carbon whose atoms are joined in a chicken-wire-like lattice, behaves quite differently depending on the nature of material it's wrapped around.
When sheets of graphene are placed on substrates made of different materials, fundamental properties – such as how the graphene conducts electricity and how it interacts chemically with other materials – can be drastically different, depending on the nature of the underlying material.
''We were quite surprised'' to discover this altered behavior, says Michael Strano, the Charles and Hilda Roddey Professor of Chemical Engineering at MIT, who is the senior author of a paper published this week in the journal Nature Chemistry. ''We expected it to behave like graphite'' – a well-known form of carbon, used to make the lead in pencils, whose structure is essentially multiple layers of graphene piled on top of each other.
But its behaviour turned out to be quite different. ''Graphene is very strange,'' Strano says. Because of its extreme thinness, in practice graphene is almost always placed on top of some other material for support. When that material underneath is silicon dioxide, a standard material used in electronics, the graphene can readily become ''functionalised'' when exposed to certain chemicals. But when graphene sits on boron nitride, it hardly reacts at all to the same chemicals.
''It's very counterintuitive,'' Strano says. ''You can turn off and turn on graphene's ability to form chemical bonds, based on what's underneath.''