This image shows a gold nanosheet that is just two atoms thick; it has been artificially colored. Image: University of Leeds.
This image shows a gold nanosheet that is just two atoms thick; it has been artificially colored. Image: University of Leeds.

Scientists at the University of Leeds in the UK have created a new form of gold that is just two atoms thick – the thinnest unsupported gold ever created. The scientists measured the thickness of the gold at just 0.47nm.

The material is regarded as two-dimensional (2D) because it comprises just two layers of atoms sitting on top of one another. All the atoms are surface atoms – there are no 'bulk' atoms hidden beneath the surface. According to the scientists, this material could have various applications in the medical device and electronics industries – and could also find use 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 gold nanoparticles, which are three-dimensional materials with the majority of their atoms residing in the bulk rather than at the surface. The scientists believe the new material could also form the basis for artificial enzymes that could be applied in rapid, point-of-care medical diagnostic tests and water purification systems. They report the 2D gold in a paper in Advanced Science.

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

The research team are now looking to work with industry on ways of scaling-up the synthesis process. This currently takes place in an aqueous solution and starts with chloroauric acid, an inorganic substance that contains gold. This substance 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 2D gold's nanoscale dimensions, it appears green in water – and given its shape, the researchers describe it as gold nanoseaweed.

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

"Gold is a highly effective catalyst," he said. "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 the nanoscale gold sheets were 10 times more efficient than the catalytic gold nanoparticles conventionally used by industry.

"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," Evans said. Similar benchmark tests revealed that the gold sheets could even 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.

Evans thinks there will inevitably be comparisons made between the 2D gold and the very first 2D material ever created – graphene, which was first fabricated at the University of Manchester in 2004.

"The translation of any new material into working products can take a long time and you can't force it to do everything you might like to," he explained. "With graphene, people have thought that it could be good for electronics or for transparent coatings – or as carbon nanotubes that could make an elevator to take us into space because of its super strength.

"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."

This story is adapted from material from the University of Leeds, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.