Workforce makes use of plastic to make tremendous mild 18-carat gold

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Researchers have created an extremely light-weight 18-carat gold, utilizing a matrix of plastic rather than metallic alloy components.

The invention will thrill lovers of gold watches and heavy jewellery. The objects of their want could sometime turn into a lot lighter, however with out dropping any of their glitter.


Particularly in watches, a small quantity of weight could make all of the distinction. Nobody desires to put on a heavy watch on their wrist, even when it’s fabricated from actual gold. After a time, it turns into uncomfortable and annoying.

Researchers got down to create a brand new type of gold that weighs about 5 to 10 instances lower than conventional 18-carat gold. The standard combination is often three-quarters gold and one-quarter copper, with a density of about 15 g/cm3.

That’s not true for the brand new light-weight gold: its density is simply 1.7 g/cm3. And nonetheless it’s nonetheless 18-carat gold. How did researchers obtain this miraculous lightness?

As a substitute of a metallic alloy component, Leonie van ‘t Hag, previously a postdoc within the lab of Raffaele Mezzenga, professor of meals and smooth supplies at ETH Zurich, and colleagues used protein fibers and a polymer latex to type a matrix through which they embedded skinny discs of gold nanocrystals. As well as, the light-weight gold incorporates numerous tiny air pockets invisible to the attention.

The researchers’ research on this course of seems within the journal Superior Practical Supplies.

The nanoplatlets look like thin sheets of broken and cracked rocks under the microscopeGold nanoplatelets embedded in a latex matrix. (Credit score: Stephan Handschin/ScopeM/ETH Zurich)

flip plastic into gold

Right here’s how the researchers created the brand new light-weight gold: first, they added the components to water and created a dispersion. After including salt to show the dispersion right into a gel, they changed the water in it with alcohol.

Then they positioned the alcohol gel right into a strain chamber, the place excessive pressures and a supercritical CO2 environment enabled miscibility of the alcohol and the CO2 gasoline; when the strain is launched, every part turns it right into a homogeneous gossamer-like aerogel. Warmth utilized afterwards anneals the plastic polymers, reworking the fabric and compacting it into the ultimate desired form, but preserving the 18-carat composition.

“This gold has the fabric properties of a plastic,” Mezzenga says. If a chunk of it falls onto a tough floor, it seems like plastic. But it surely glimmers like metallic gold, and will be polished and labored into the specified type.

Jewellery and electronics

The researchers may even change the composition of the gold to regulate the hardness of the fabric. They will additionally change the latex within the matrix with different plastics, corresponding to polypropylene. Since polypropylene liquifies at some particular temperature, “plastic gold” made with it may mimic the gold melting course of, however at a lot decrease temperatures.

Moreover, the form of the gold nanoparticle can change the fabric’s shade: “nanoplatelets” produce gold’s typical shimmer, whereas spherical nanoparticles of gold lend the fabric a violet hue.

“As a normal rule, our strategy lets us create virtually any type of gold we select, in step with the specified properties,” Mezzenga says.

Whereas the plastic gold can be particularly demand within the manufacture of watches and jewellery, it is usually appropriate for chemical catalysis, electronics functions, or radiation shielding, Mezzenga says. The researchers have utilized for patents for each the method and the fabric.

The crew beforehand made the lightest gold in world—gold that weighed so little it might float atop cappuccino froth.

“However the materials was too unstable and couldn’t be labored,” Mezzenga says. “This time we set ourselves the clear purpose of making a light-weight gold that may additionally truly be processed and utilized in a lot of the functions the place gold is used right this moment.”

Supply: ETH Zurich

Authentic Research DOI: 10.1002/adfm.201908458