A University of Southampton team has found a way to change the colour of gold to basically any colour other than gold. Not by any chemical additions or treatments but by changing the metal’s surface to trick our brains.
Scientists have discovered that embossing tiny raised or indented patterns onto the metal’s surface can change the way it absorbs and reflects light – ensuring our eyes don’t see it as “golden”.
The same process works on other metals, like silver and aluminium. The team hopes this chemical-free breakthrough will deliver valuable economic, environmental and other benefits. The jewellery industry is one sector to be targeted by the group.
“This is the first time the visible colour of metal has been changed in this way,” said Professor Nikolay Zheludev, who led the project.
The results stem from a major initiative funded by the Engineering and Physical Sciences Research Council targeting the development of a new generation of nanotechnology-enabled materials.
“The colours of the objects we see all around us are determined by the way light interacts with those objects. For instance, an object that reflects red light but absorbs other wavelengths will appear red to the human eye,” Zheludev said.
“This is the fundamental principle we have exploited in this project. By embossing metals with patterns only around 100 nanometres across, we’ve found that we can control which wavelengths of light the metal absorbs and which it reflects.”
Depending on the precise shape and height or depth of the patterns, jewellery could elicit a number of different colours in different areas.
The nanotechnology could also be used to help prevent forgeries of bespoke pieces.
The nano-patterning is carried out at the research level using well-established techniques such as ion beam milling, which is akin to sand-blasting on the atomic scale.