1. Light, color and illumination

The word "phosphorus" was coined in the early 17th century to describe rocks that emitted light when exposed to the sun. It comes from the Greek phos, meaning "light", and phoros, meaning "that which carries"; they are light carriers! We usually distinguish between phosphorescence (light emission that lasts a long time after the excitation at its source has stopped) and fluorescence, which refers to rapid emission, such as that of fluorite (CaF ₂ ). These two notions were first brought together by a German physicist, Eilhardt Wiedemann, in 1888 under the general term luminescence. Today, the materials that produce luminescence are commonly referred to as "luminophores".

Scientific research into phosphors began over 100 years ago. Théodore Sidot, a young French...