Abstract
In modern urban life, luminescence has become an indispensable part of our daily existence, making it difficult to envision life without it. This reliance stems from the widespread use of various lighting devices, including lamps, televisions, mobile screens, LED lights, LED televisions, signals, and displays. Light, as a form of electromagnetic energy, requires another energy source for its creation. The two primary mechanisms for generating light are incandescence and luminescence.
Incandescence refers to light produced by heat energy. When certain materials are heated to sufficiently high temperatures, they begin to emit light. For example, electric heaters produce light through electric current, and metals can appear "red hot" in flames due to incandescence. In traditional incandescent light bulbs, tungsten filaments glow "white hot" by this same principle.
On the other hand, luminescence is the spontaneous emission of light from a substance that does not stem from heat. It represents a form of cold body radiation, which can occur due to chemical reactions, electrical energy, subatomic motions, or stress on a crystal. Unlike incandescence, luminescence, or "cold light," can occur at normal and lower temperatures. The term "luminescence" was officially introduced by the German physicist Eilhardt Wiedemann in 1888, derived from the Latin word "lumen," meaning "light." Substances that exhibit luminescence are referred to as "luminescent materials" or "phosphors," a term meaning "light bearer" in Greek, first coined by the Italian alchemist Vincentinus Casciarolo in the 17th century. Casciarolo discovered a glowing stone, likely barite (BaSO4), which emitted red light in the dark after being exposed to sunlight, although he was originally seeking to transform it into a noble metal [1].
In 1866, Theodore Sidot synthesized zinc sulfide (ZnS), which became the prototype for phosphors used in contemporary cathode ray tubes. Between the late 19th and early 20th centuries in Germany, Philip E.A. Lenard and his colleagues explored various phosphors, incorporating different rare earth ions along with heavy metal ions into various host materials [2].
The process of luminescence involves an energy source exciting an electron in an atom from its "ground" (lowest energy) state to an "excited" (higher energy) state. The electron then releases the energy as visible light, allowing it to return to its ground state. Luminescence can be observed in natural phenomena such as glowworms, fireflies, and certain marine bacteria and deep-sea creatures. This phenomenon has been utilized across many fields including archaeology, geology, biomedical engineering, chemistry, physics, and various industrial applications for quality control and research and development [3].