Scientists create the world's thinnest gold

Scientists at the University of Leeds have created a new form of gold which is just two atoms thick - the thinnest unsupported gold ever created.

The researchers measured the thickness of the gold to be 0.47 nanometres - that is one million times thinner than a human finger nail. The material is regarded as 2D because it comprises just two layers of atoms sitting on top of one another. All atoms are surface atoms - there are no 'bulk' atoms hidden beneath the surface. 

The material could have wide-scale applications in the medical device and electronics industries - and also as a catalyst to speed up chemical reactions in a range of industrial processes.

Laboratory tests show that the ultra-thin gold 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. 

The University of Leeds is recognised for its research in material science. It runs the Bragg Centre, where academics from a range of disciplines collaborate.

The scientists used electron microscopy and analysis facilities run by the School of Chemical and Process Engineering to carry out  parts of their research.

New possibilities

Scientists believe the new material could also form the basis of artificial enzymes that could be applied in rapid, point-of-care medical diagnostic tests and in water purification systems.

The announcement that the ultra-thin metal had been successfully synthesised was made in the journal Advanced Science. 

The lead author of the paper, Dr Sunjie Ye, from Leeds' Molecular and Nanoscale Physics Group and the Leeds Institute of Medical Research, said: "This work amounts to a landmark achievement. 

"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.
 

This method could innovate nanomaterial manufacturing.

Dr Sunjie Ye, University of Leeds


The research team are looking to work with industry on ways of scaling-up the process.

More efficient by tenfold

Synthesising the gold nanosheet takes place 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, just two atoms thick.

Because of the gold's nanoscale dimensions, it appears green in water - and given its shape, the researchers describe it as gold nanoseaweed. 

Images taken from an electron microscope reveal the way the gold atoms have formed into a highly organised lattice. Other images show gold nanoseaweed that has been artificially coloured.

Gold lattice structure

This electron microscope picture shows the gold atoms' lattice structure

Professor Stephen Evans, head of the Leeds' Molecular and Nanoscale Research Group who supervised the research, said the considerable gains that could be achieved from using these ultra-thin gold sheets are down to their high surface-area to volume ratio.

He said: "Gold is a highly effective catalyst. Because the nanosheets are so thin, just about every gold atom plays a part in the catalysis. It means the process is highly efficient."

Standard benchmark tests revealed that gold nanoscale sheets were ten times more efficient than the gold nanoparticles conventionally used in industry. 

Professor Evans said: "Our data suggests that industry could get the same effect from using a smaller amount of gold, and this has economic advantages when you are talking about a precious metal."

...industry could get the same effect from using a smaller amount of gold, and this has economic advantages when you are talking about a precious metal.

Professor Steven Evans, University of Leeds


Similar benchmark tests revealed that the gold sheets could act as highly effective artificial enzymes.

The flakes are also flexible, meaning they could form the basis of electronic components for bendable screens, electronic inks and transparent conducting displays.

X ray diffusion

Dr Sunjie Ye and Professor Stephen Evans used x-ray photo electron spectroscopy to confirm the purity of the new form of gold

Professor Evans said: "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.

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.

Professor Stephen Evans, University of Leeds

The University of Leeds’ Bragg Centre has access to some of the best facilities in the world.