Scientists have developed an incredibly light gold foam that can even float on the milk foam. The 20 carat gold nugget is nearly 1000 times lighter than the conventional forms of the precious yellow metal. What’s even more interesting is that although the new form of gold looks similar to conventional gold and can’t be differentiated by the naked eyes but still it is lighter than water and nearly as light as air.
To design such thing from gold that can float over milk foam, lead researcher Raffaele Mezzenga, Professor of Food and Soft Materials at ETH Zurich, made a porous structure by using a three-dimensional mesh which contains 98 percent air and only 2 percent solid metal. The new gold is kind of an aerogel with metallic shine which is malleable by hand.
In 2 percent solid material, more than four-fifth is gold and less than one-fifth is milk protein fibrils. This corresponds to around 20 carat gold. To create the porous material, researchers first developed nanometre-fine protein fibres by heating the milk proteins. Later, scientists used these nanometre-fine protein fibres with the solution if gold salt to create the aerogel. Mezzenga explained that protein fibres formed a crystalline structure of small particles with the gold salt.
Now the big problem was to dry the aerogel to form a solid structure as the direct air drying could have damaged the uniform gold structure. To overcome this problem, scientists used Carbon Dioxide which slowly dries the aerogel without deteriorating the gold composition. In addition, colour of the gold can be changed since it’s optical properties depend on the size of the gold particles. Changing the reaction to make gold crystallise into nanoparticles instead of nanoparticles result in a dark-red coloured gold.
The research appeared in the journal Advanced Materials.