Submission + - Romans Used Nanotechnology to Turn Lycurgus Cup From Green to Red 1,600 Years Ag (ibtimes.co.uk)
In order to produce the dichroic effect on the Lycurgus Cup, Roman artisans are believed to have ground down particles of gold and silver to 50 nanometres in diameter, which is less than one-thousandth the size of a grain of table salt, and then laid these nanoparticles within the glass before it set. No one has been able to replicate the effect, until now.
The researchers created nanoscale metallic nanoparticle arrays from a thin layer of silver that mimic the dichroic colour effect of the Roman chalice to create multicoloured holograms containing 16 million nanoparticles per square millimetre.
Each nanoparticle scatters light into numerous colours depending on its size and shape, and the light, when put together, produces an image.