Woah! New gold aerogel is 98 percent air, floats on water

Scientists from ETH Zurich claim that they have created the lightest gold nugget ever: a type of the precious metal made from real 20 carat gold that is said to be 1,000 times lighter than normal– light enough to float on top of the milk foam in a cappuccino.

Their work, reported in the November 23 edition of the journal Advanced Materials, is basically a three-dimensional porous foam aerogel made out of gold, an according to Raffaele Mezzenga, the professor of food and soft materials that led the research, it is even lighter than water.

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(Credit: Gustav Nyström and Raffaele Mezzenga/ETH Zurich)

In fact, Mezzenga and his colleague claim that the substance is almost as light as air and nearly indistinguishable from regular gold to the naked eye. The aerogel even has a metallic shine, he explained. However, as it is made from 98 parts air and old two parts solid material (80 percent of which is gold and 20 percent of which is milk protein fibrils), it is soft and malleable.

The foam’s color, reflectivity and absorption can be altered

The substance is created by heating milk proteins to create nanometer-scale amyloid fibrils, or protein fibers which are then put into a solution of gold salt, the researchers explained. The fibers become interlaced into a basic structure along with crystallized gold particles, creating a network of gold fibers that is dried using carbon dioxide to prevent damage to the structure.

The process, in which gold particles are crystallized during the actual manufacture of the aerogel protein structure instead of added to a pre-existing scaffold, is new and makes it easier to end up with a homogeneous substance that is an exact copy of gold alloys. Furthermore, the authors said that this method makes it possible to easily manipulate the properties of gold along the way.

“The optical properties of gold depend strongly on the size and shape of the gold particles,” said first author Gustav Nyström, a postdoc at ETH Zurich. “Therefore we can even change the color of the material. When we change the reaction conditions in order that the gold doesn’t crystallize into microparticles but rather smaller nanoparticles, it results in a dark-red gold.”

In addition to influencing the color, this method allows them to alter other properties of the gold, such as absorption and reflection. The researchers believe this foam could be used in many of the same application which currently require regular gold, proving a smaller, lightweight and porous alternative to the metal, including pressure sensors.

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