Scientists have presented a new type of foam created out of real gold, touted to be the lightest form of the precious metal ever produced and useful for many practical applications.
A nugget of genuine 20-carat gold – said to be a thousand times lighter than conventional gold, so light that it floats on the milk foam of a cappuccino – is said to be accomplished by a research team from ETH Zurich in Switzerland.
Introduced in the journal Advanced Materials, the gold foam is a three-dimensional mesh of the metal mostly consisted of pores. The lead scientist, Professor Raffaele Mezzenga, said the aerogel has a metallic sheen and is “lighter than water” and nearly “as light as air.”
Soft and malleable, the gold foam is 98 parts air and two parts solid material, of which over four-fifths are gold and less than a fifth is milk protein fibrils. This is estimated to be 20-carat gold.
How did the scientists come up with this porous material?
First, they heated milk proteins, creating nanometer-grain protein fibers. These amyloid fibrils are placed in a gold salt solution and came together for the gold to simultaneously crystallize into tiny particles.
"One of the big challenges was how to dry this fine [gold] network without destroying it," shared first study author Gustav Nyström, pertaining to how air-drying can potentially damage the gold structure.
The team then chose a mild yet labor-intensive process of drying using carbon dioxide – a technique that makes it easy to achieve a “homogenous gold aerogel” ideal to mimic gold alloys.
The scientists can also change the color of the material through manipulating the gold’s particle size, resulting in a dark-red gold. They can also influence other optical properties such as reflection and absorption.
More than making for a unique, interesting innovation, the gold foam can be used in several real-life applications, such as in optics and watch and jewelry making. It can also play a role in chemical catalysis, because of the highly porous material’s huge surface, chemical reactions depending on gold can be made more efficient.
Pressure sensors can also be manufactured with this gold foam. Mezzenga explained that gold particles do not touch at normal atmospheric pressure, which then makes the aerogel non-conductive.
"But when the pressure is increased, the material gets compressed and the particles begin to touch, making the material conductive,” he explained.
