Team changes colour of gold by altering surface structure

In what is claimed to be a world first, researchers at Southampton University have demonstrated that by embossing nanoscale raised or indented patterns onto the metal’s surface they can change its colour without using coatings or chemical treatments.

This technique, which could also be applied to other metals, could be used in jewellery manufacture or in the security industry to create banknotes or other items with sophisticated optical properties that would be almost impossible to imitate.

According to the group at the university’s Centre for Photonic Metamaterials, the behaviour of the light striking the metal (and therefore the colour that is created) can be modified simply by varying the shape and height of these patterns in order to produce a wide range of colours.

Developed through the £5m EPSRC-funded ‘Nanostructured Photonic Metamaterials’ initiative, the breakthrough is one of the latest additions to the field of structural colour, in which materials are coloured not through dye or pigmentation but through the way in which light interacts with tiny structures on a material’s surface. The iridescent greens and blues of beetles are an example of this phenomenon occurring naturally.