Gold and Silver Dichroic Nanocomposite in the Quest for 3D Printing the Lycurgus Cup

The Lycurgus cup is worldwide admired in particular because of its fascinating dichroic property. The cup presents a green colour when the observer and the light source are on the same side (reflection), and a deep red colour when the observer and the light source are at opposite sides (transmission). This peculiar effect, which has perplexed scientists for centuries, was discovered to be due to the presence of nanoparticles in the glass. In particular, to two different metallic nanoparticles: silver nanoparticles (AgNP) and gold nanoparticles (AuNP). Here we show how dichroic silver nanoparticles and gold nanoparticles can be embedded in a 3D printable material in order to reproduce the same dichroic effect of the original Lycurgus cup.