Real gold in super light
A new material has been developed at ETH Zurich that consists of three quarters gold and three quarters air. It works thanks to latex and milk protein.
It looks like solid gold, it can be melted and polished - but it weighs only a fraction of what normal jewellery gold would weigh. Nevertheless, the new material produced by a research group led by Leonie van't Hag from ETH Zurich is no fake: it is real, 18-carat gold, the team reports in Advanced Functional Materials, with the precious metal making up three quarters of the mass. Thanks to a technical trick, however, air-filled pores take up around three quarters of the material's volume. Metal foams based on this model have been around for a long time, but gold and its alloys are too soft, meaning that such materials collapse under load. The solution to the problem is a gel made up of gold nanoplatelets and the plastic polystyrene. The nanoplatelets not only provide the golden colour, but also ensure that the surface can be polished to a shiny finish. The plastic, on the other hand, stabilises the porous structure. The material could be used as light gold jewellery, but its properties in particular close a gap and could enable previously unknown applications.
One advantage of the material is its environmentally friendly manufacturing process, which does not require toxic solvents, the working group writes in the publication. The material is created by mixing polystyrene latex - a colloid of nanometre-sized plastic beads in water - with a solution of milk protein fibres and a gold salt at the correct pH value. The gold nanoplatelets are formed from the dissolved gold and the milk protein, and a plastic gel is created from the colloid.
The team then removed the water from this gel using supercritical carbon dioxide and heated the resulting material to 190 degrees Celsius, forming a stable block that consisted of three quarters gold - and three quarters air. Whether the material will really make a career as super-light gold jewellery may be doubtful - a well-known Bond villain once praised its "divine heaviness" - but the precious metal has a whole range of technical applications, including as a catalyst and as shielding, which could benefit from the new method.
Spectrum of Science
We are a partner of Spektrum der Wissenschaft and want to make sound information more accessible to you. Follow Spektrum der Wissenschaft if you like the articles.
[[small:]]
Experts from science and research report on the latest findings in their fields – competent, authentic and comprehensible.
Practical solutions for everyday problems with technology, household hacks and much more.
Show all
