Luminesiteit

Luminesiteit is a term that refers to the emission of light by a substance that has not been heated, a process that contrasts with incandescence. It encompasses several phenomena, including fluorescence, phosphorescence, chemiluminescence, bioluminescence, and triboluminescence. In fluorescence, the material absorbs photons at a higher energy level and promptly re-emits them at a lower energy; the emitted light usually ceases almost immediately when the excitation source is removed. Phosphorescence differs in that the excited state has a longer lifetime, so the material continues to glow after the excitation has stopped. Chemiluminescence involves the release of light during a chemical reaction, while bioluminescence is the biological analogue of chemiluminescence, seen in fireflies, certain marine organisms, and some fungi. Triboluminescence occurs when a material emits light as a result of mechanical action such as crushing or rubbing.

The underlying mechanism often involves electronic transitions within molecules or ions. An electron in a higher energy orbital can relax to a lower energy state, releasing excess energy as a photon. In many cases, the material or the surrounding matrix plays a role in guiding the emitted photons, leading to observable effects such as glow-in-the-dark stickers (phosphors) or luminous contour paper. Applications of luminesiteit are broad: from medical imaging dyes and diagnostic assays that rely on fluorescence, to LEDs that use phosphors to convert blue or ultraviolet light into the full spectrum of visible light, and to security inks that fluoresce under ultraviolet illumination. Current research in materials science aims to improve quantum efficiencies, broaden color spectra, and develop new luminescent compounds for use in displays, sensors, and energy conversion devices.