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Scientists Create Lightest Form of Gold Made of 98 % of Air

Scientists from Switzerland have created the lightest form of gold which consists of 98 % of air, and 20-carat gold, as well as milk protein fibres. The findings are available in the journal Advanced Materials.

A piece of the new form of golf topping a latte. Photo credits: ETH Zurich.

A piece of the new form of gold topping a latte. Photo credits: ETH Zurich.

Researcher Raffaele Mezzenga from ETH Zurich and his team created the new type of gold from a 3D meshwork made mostly of pores – up to 98 %. Four-fifths of the rest (the 2 % ) contains 20-carat gold, while one-fifth of it comprises milk protein in the form of nano-strings.

The milk proteins were first heated to turn them into small fibres called amyloid fibrils which were then incorporated into a gold salt solution to make them interlocked. The basic structure was thus produced, allowing the gold particles to crystallise into finer pieces (microparticles).

The end result was a gold fibre network-gel that was later subjected to a process called “supercritical drying” – used to decaffeinate coffee – in order to preserve the delicate network of milk protein fibres and gold.

The researchers took it a step further to give colour to their aerogel: they modified reaction conditions that caused the gold to crystallise into nanoparticles (instead of microparticles as before). This time, the end result was a dark-red gold.

From left to right: A foam of amyloid protein fibres without gold; Gold aerogel made of gold microparticles; Gold aerogel with gold nanoparticles. Photo credits: Nyström G et al. Advanced Materials 2015.

From left to right: A foam of amyloid protein fibres without gold; Gold aerogel made of gold microparticles; Gold aerogel with nanoparticles. Photo credits: Nyström G et al. (Advanced Materials 2015).

Bearing a metallic and shiny appearance, the aerogel is much lighter than standard gold; as Mezzenga points out, it is a thousand times lighter than existing gold alloys, and is “lighter than water”.

The “gold aerogel” displays features that could make of it suitable for applications other than jewellery-making. Just like its optical properties have been changed to give off other colours, its rate of absorption and reflection can also be manipulated. The researchers believe it could potentially be used as chemical catalyst, specially because of the large surface area provided by the pores. It might also be put to use in the manufacture of tiny pressure sensors.

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