Commentary: Luster ceramics: a 9th century AD nanotechnology

Abstract

Photonic crystals are composed of periodic metallo-dielectric nanostructures that affect the propagation of light. The concept was proposed by Yablonovitch 25 years ago and today is an active, ongoing field of research with high prospects for potential applications in the field of photonics. It is known that nature has provided such nanostructures in minerals and living creatures. Sparkling opals, consisting of submicron size silica spheres arranged in a face-centered cubic structure, the iridescent tail feathers of the peacock, or the Morpho butterfly's blue shining color wings consisting of regular rows of thin plates so-called scales, are examples. We can refer to the brilliancy of these colors resulting from reflection and diffraction in the nano-structured material as structural colors, in contrast to pigmentary colors that result from absorption of light by pigments. Yet, in the early Middle Ages, in the 9th century AD, Islamic potters in Iraq succeeded in decorating glazed ceramics with vivid colors showing iridescent effects, very much like structural colors. These have been revealed to be caused by metallic nanoparticles buried below the glaze surface that the ancient potters were able to diffuse through empirical, carefully controlled heat treatments.