New deeply coloured 18-K gold materials built by nanotechnologies

A new way to elaborate coloured carat gold materials has been developed. Instead of using traditional metallurgy route, we built a new 18-K bulk material using nanostructured gold particles. The resulting colour is the consequence of a well-known property of gold nanoparticles: the surface plasmon resonance effect. Depending on the chemical environment around the nanoparticles, their shape and size, it is possible to tune the colour of gold. Thanks to this property, it is possible to obtain a large panel of colours not achievable via conventional alloying route. Here, we focus on one hybrid nanostructured material: Au-SiO₂. The development of a new synthesis route enables us to obtain nanostructured micrometric powders that can then be pressed to obtain a bulk material. The resulting nanocomposites are characterized by means of energy-dispersive X-ray spectroscopy (EDX), fire assay, TEM and spectrophotocolorimetry. All these characterizations have shown that our composites exhibit a gold content superior to 75?% by weight and have a much more vivid colour than classical coloured gold. The new composites are therefore deeply coloured 18-K materials.