Optical Properties
Metallic nanophases - Definitions, processing and properties

Optical properties are a classic example of the nano-transition effect, because they are both visible and have a long history, having been used by glass artisans as far back as the Middle Ages. Figure 15 shows a few examples. The coloration is due to the optical response of metallic nanoparticles, first observed by Faraday as early as 1857. Two questions arise:

• What is the origin of the coloration?

• How can the glass remain transparent despite the presence of solid particles?