British scientists have unveiled what they say is the thinnest unsupported gold ever created.
At just 0.47 nanometres – one million times thinner than a human finger nail – it is regarded as 2D because it is just two layers of atoms sitting on top of one another. In other words, all atoms are surface atoms: there are no “bulk” atoms hidden beneath the surface.
The research team from the University of Leeds believes the material could have wide-scale applications in the medical device and electronics industries, and as a catalyst to speed up chemical reactions in a range of industrial processes.
Writing in the journal Advanced Science, they say laboratory tests showed it is 10 times more efficient as a catalytic substrate than the currently used gold nanoparticles, which are 3D materials with the majority of atoms residing in the bulk rather than at the surface.
“This work amounts to a landmark achievement,” says lead author Sunjie Ye. “Not only does it open up the possibility that gold can be used more efficiently in existing technologies, it is providing a route which would allow material scientists to develop other 2D metals.”
The nanosheet is synthesised in an aqueous solution. and starts with chloroauric acid, an inorganic substance that contains gold. It is reduced to its metallic form in the presence of a confinement agent: a chemical that encourages the gold to form as a sheet.
It appears green in water and, given its shape, the researchers call it gold “nanoseaweed”.
Co-author Stephen Evans says much of the value of such ultra-thin sheets lies in their high surface-area to volume ratio.
“Gold is a highly effective catalyst,” he says. “Because the nanosheets are so thin, just about every gold atom plays a part in the catalysis. It means the process is highly efficient.”
The flakes are also flexible, so they could form the basis of electronic components for bendable screens, electronic inks and transparent conducting displays.
Evans says there will inevitably be comparisons made between 2D gold and the first 2D material ever created – graphene, which was fabricated at the University of Manchester, UK, in 2004.
“I think with 2D gold we have got some very definite ideas about where it could be used, particularly in catalytic reactions and enzymatic reactions,” he says.
“We know it will be more effective than existing technologies, so we have something that we believe people will be interested in developing with us.”