Tag Archives: jewellery

Solid gold smoke?

Aerogels seem to enchant even scientists who sometimes call it ‘solid smoke’ (my Aug. 20, 2012 posting). This latest aerogel is made of gold according to a Nov. 25, 2015 news item on Nanowerk,

 A nugget of real 20 carats gold, so light that it does not sink in a cappuccino, floating instead on the milk foam – what sounds unbelievable has actually been accomplished by researchers from ETH Zurich. Scientists led by Raffaele Mezzenga, Professor of Food and Soft Materials, have produced a new kind of foam out of gold, a 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,” says Mezzenga.

A Nov. 25, 2015 ETH Zurich press release (also on EurekAlert), which originated the news item, provides more information about the ‘gold smoke’,

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 are gold and less than one-fifth is milk protein fibrils. This corresponds to around 20 carat gold.

Here’s what it looks like,

Caption: Even when it seems unbelievable: these are genuine photographs, in which nothing has been faked. E.g. the 20 carats gold foam is lighter than milk foam. Credit: Gustav Nyström and Raffaele Mezzenga / (copyright) ETH Zurich

Caption: Even when it seems unbelievable: these are genuine photographs, in which nothing has been faked. E.g. the 20 carats gold foam is lighter than milk foam.
Credit: Gustav Nyström and Raffaele Mezzenga / (copyright) ETH Zurich

The press release provides more technical details,

The scientists created the porous material by first heating milk proteins to produce nanometre-fine protein fibres, so-called 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.

“One of the big challenges was how to dry this fine network without destroying it,” explains Gustav Nyström, postdoc in Mezzenga’s group and first author of the corresponding study in the journal Advanced Materials. As air drying could damage the fine gold structure, the scientists opted for a gentle and laborious drying process using carbon dioxide. They did so in an interdisciplinary effort assisted by researchers in the group of Marco Mazzotti, Professor of Process Engineering.

Dark-red gold

The method chosen, in which the gold particles are crystallised directly during manufacture of the aerogel protein structure (and not, for example, added to an existing scaffold) is new. 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 in a simple manner. ” The optical properties of gold depend strongly on the size and shape of the gold particles,” says Nyström. “Therefore we can even change the colour of the material. When we change the reaction conditions in order that the gold doesn’t crystallise into microparticles but rather smaller nanoparticles, it results in a dark-red gold.” By this means, the scientists can influence not only the colour, but also other optical properties such as absorption and reflection.

The new material could be used in many of the applications where gold is currently being used, says Mezzenga. The substance’s properties, including its lighter weight, smaller material requirement and porous structure, have their advantages. 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. Finally, the scientists have also shown how it becomes possible to manufacture pressure sensors with it. “At normal atmospheric pressure the individual gold particles in the material do not touch, and the gold aerogel does not conduct electricity,” explains Mezzenga. “But when the pressure is increased, the material gets compressed and the particles begin to touch, making the material conductive.”

Here’s a link to and a citation for the paper,

Amyloid Templated Gold Aerogels by Gustav Nyström, Maria P. Fernandez-Ronco, Sreenath Bolisetty, Marco Mazzotti, Raffaele Mezzenaga. Advanced Materials DOI: 10.1002/adma.201503465 First published: 23 November 2015

This paper is behind a paywall.

Gold Light jewellery courtesy of gold nanoparticles and designers in Spain

Nanowerk is featuring a Dec. 21, 2012 news item about a jewellery project from the Institut Català de Nanotecnologia (ICN) Note: Links have been removed,

The Centre for NanoBioSafety and Sustainability (CNBSS) organised the premiere of Gold Light, the first quantum jewellery product, last week at the Hotel Mercer, in Barcelona [Spain]. Gold Light is the fruit of a collaboration that combines Barcelona’s long artisanal tradition with Nanotechnology developed by Institut Català de Nanotecnologia (ICN)’s Inorganic Nanoparticles Group. Gold Light is an extraordinary jewellery product, unique for both its innovation and its aesthetics.

The ICN’s Dec. 13, 2012 news release provides more detail (which originated the news item on Nanowerk),

A multidisciplinary team, including jewellery designer Roberto Carrascosa, artist Joan Peris, production designer Francesc Oliveras, and art business manager Jose Luis Fettolini, developed Gold Light over the course of a year, based on specialist knowledge from the Inorganic Nanoparticles Group. The final product exploits the aesthetic potential of noble-metal nanoparticles and their special interaction with light. Jewellers traditionally work with precious metals, which in their smallest form exist as nanoparticles(at smaller sizes, metal particles lose their metallic properties). Gold Light, composed of gold nanoparticles, represents the advent of quantum jewellery, where quantum is used in the literal sense. Their work on Gold Light has also served as a case model for the CNBSS to evaluate the regulatory mechanisms and corporate obligations for the development and marketing of a product that contains nanoparticles. For the CNBSS, the venture served as a study in the safety-by-design of a nanoproduct, through advice from attorney Ignasi Gispert.

Here’s what one of the pieces looks like,

The distinctive colours of Gold Light jewellery derive from different types of gold nanoparticles.

The distinctive colours of Gold Light jewellery derive from different types of gold nanoparticles.

You can see more on the Gold Light jewellery website but you won’t find any technical information about the colour differences or information about how to purchase.