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Scientists create ‘goldene’ – a single atom layer of gold

In a first, researchers in Sweden have created sheets of gold that are only a single atom layer thick and could be used in a variety of interesting applications

(From left) Lars Hultman, professor of thin film physics and Shun Kashiwaya, researcher at the Materials Design Division at Linköping University.
(From left) Lars Hultman, professor of thin film physics and Shun Kashiwaya, researcher at the Materials Design Division at Linköping University. (Credit: Olov Planthaber)

For a long time, scientists have tried to create single-atom-thick sheets of gold that could be used for a variety of applications. But it remained a challenge because of the metal’s tendency to lump together.

Now researchers from Linköping University, Sweden have created sheets of gold that are only a single atom layer thick. They call the material 'goldene’ (a la graphene). According to the researchers, this has given the gold new properties that can make it suitable for use in applications such as CO2 conversion, hydrogen production, and production of value-added chemicals. The findings of the study were published recently in the journal Nature Synthesis.

Also read: Japan's hand-forged knives are a slice of samurai metallurgy

To overcome their previous struggles with the process, the researchers used a 100-year-old method used by Japanese smiths – called Murakami’s reagent. “If you make a material extremely thin, something extraordinary happens – as with graphene. The same thing happens with gold. As you know, gold is usually a metal, but if single-atom-layer thick, the gold can become a semiconductor instead,” Shun Kashiwaya, researcher at the Materials Design Division at Linköping University, says in a news release.

To create goldene, the researchers used a three-dimensional base material where gold is embedded between layers of titanium and carbon, the release explains. But making the final version of goldene was still challenging. “We had created the base material with completely different applications in mind. We started with an electrically conductive ceramics called titanium silicon carbide, where silicon is in thin layers. Then the idea was to coat the material with gold to make a contact. But when we exposed the component to high temperature, the silicon layer was replaced by gold inside the base material,” Lars Hultman, professor of thin film physics at Linköping University, says in the release.

This is when Hultman came across Murakami’s reagent, which etches away carbon residue and changes the colour of steel in knife making, for instance. This process has been used in Japanese forging art for over a century. But Kashiwaya had to make certain modifications since the exact same process could not be used here. Kashiwaya tried different concentrations of Murakami’s reagent and different time spans for etching – ranging from days to months. The etching was also had to be carried out in the dark as cyanide develops in the reaction when it is struck by light, and it dissolves gold.

The final step, the release explains, was to get the gold sheets stable. To prevent the exposed two-dimensional sheets from curling up, a surfactant was added in this instance. “The goldene sheets are in a solution, a bit like cornflakes in milk. Using a type of “sieve”, we can collect the gold and examine it using an electron microscope to confirm that we have succeeded. Which we have,” Kashiwaya says in the release.

With goldene, future applications could include hydrogen production, water purification, communication, and much more. Moreover, the amount of gold used in applications today can be much reduced, the release adds.

The next step for the LiU researchers is to investigate whether they can replicate the same process with other noble metals.

Since gold is an excellent conductor of heat and electricity, it is used extensively in the electronics industry: in everything from printed circuits to transistors. Computer circuitry, calculators, TVs, telephones, and fire detectors are also often plated with gold.

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