TECH SPECIAL.... Scientists make real gold as light as air

Scientists make real gold  as light as air   The gold foam consists of 98 parts air and only two parts of  solid material.  Of this solid material, more than four-fifths is gold and less than one-fifth is milk protein fibrils, corresponding to around  20 carat of gold Researchers at ETH Zurich have created anew type of foam made of real  gold.  It is the lightest form ever produced of the precious metal: a thousand times lighter than its conventional form and yet it is nearly impossible to tell the difference with the naked eye. Scientists, led by Raffaele Mezzenga, Professor of Food and Soft Materials,  produced the three-dimensional mesh of gold that consists mostly of pores. It is the lightest gold nugget ever created. “The so-called aerogel is a thousand times lighter than conventional gold alloys. It is lighter than water and almost as light as air,“ said Mezzenga. The new gold form can hardly be differentiated from conventional gold  with the naked eye ­ the aerogel even has a metallic shine. But in contrast to its conventional form, it is soft and malleable by hand. It consists of 98 parts air and only two parts of solid material. Of this solid material, more than four-fifths is gold and less than one-fifth is milk protein fibrils. This corresponds to around 20 carat gold. The scientists created the porous material by first heating milk proteins to  produce nanometre-fine protein fibres, or amyloid fibrils, which they then  placed in a solution of gold salt. The protein fibres interlaced themselves into a basic structure along which  the gold simultaneously crystallised into small particles. This resulted in a  gel-like gold fibre network. As air drying could damage the fine gold structure, the scientists opted for a gentle and la borious process using carbon dioxide. The method's biggest  advantage is that it makes it easy to obtain a homogeneous gold aerogel,  perfectly mimicking gold alloys. The manufacturing technique also offers scientists numerous possibilities to deliberately influence the properties of gold. The new material could be used in many of the applications where gold is currently being used, said Mezzenga. Applications in watches and jewellery are only one possibility. Another application demonstrated by the scientists is chemical catalysis: since the highly porous material has a huge surface, chemical reactions that depend on the presence of gold can be run in a very efficient manner. The material could also be used in applications where light is absorbed or reflected. The scientists have also shown how it becomes possible to  manufacture pressure sensors with it. MM27NOV15