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Luminescence
Luminescence is a spontaneous emission of radiation from an electronically or vibrationally excited species not in thermal equilibrium with its environment. A luminescent object emits ''cold light'' in contrast to incandescence, where an object only emits light after heating. Generally, the emission of light is due to the movement of electrons between different energy levels within an atom after excitation by external factors. However, the exact mechanism of light emission in vibrationally excited species is unknown. The dials, hands, scales, and signs of aviation and navigational instruments and markings are often coated with luminescent materials in a process known as ''luminising''. Types * Ionoluminescence, a result of bombardment by fast ions * Radioluminescence, a result of bombardment by ionizing radiation * Electroluminescence, a result of an electric current passed through a substance ** Cathodoluminescence, a result of a luminescent material being struck by elect ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bioluminescence
Bioluminescence is the emission of light during a chemiluminescence reaction by living organisms. Bioluminescence occurs in multifarious organisms ranging from marine vertebrates and invertebrates, as well as in some Fungus, fungi, microorganisms including some bioluminescent bacteria, Dinoflagellate, dinoflagellates and terrestrial arthropods such as Firefly, fireflies. In some animals, the light is bacteriogenic, produced by symbiosis, symbiotic bacteria such as those from the genus ''Vibrio''; in others, it is autogenic, produced by the animals themselves. In most cases, the principal chemical reaction in bioluminescence involves the reaction of a substrate called luciferin and an enzyme, called luciferase. Because these are generic names, luciferins and luciferases are often distinguished by the species or group, e.g. firefly luciferin or Vargulin, cypridina luciferin. In all characterized cases, the enzyme Catalysis, catalyzes the Redox, oxidation of the luciferin resultin ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sonoluminescence
Sonoluminescence is the emission of light from imploding bubbles in a liquid when excited by sound. Sonoluminescence was first discovered in 1934 at the University of Cologne. It occurs when a sound wave of sufficient intensity induces a gaseous cavity within a liquid to collapse quickly, emitting a burst of light. The phenomenon can be observed in stable single-bubble sonoluminescence (SBSL) and multi-bubble sonoluminescence (MBSL). In 1960, Peter Jarman proposed that sonoluminescence is thermal in origin and might arise from microshocks within collapsing cavities. Later experiments revealed that the temperature inside the bubble during SBSL could reach up to . The exact mechanism behind sonoluminescence remains unknown, with various hypotheses including hotspot, '' bremsstrahlung'', and collision-induced radiation. Some researchers have even speculated that temperatures in sonoluminescing systems could reach millions of kelvins, potentially causing thermonuclear fusion; this i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Triboluminescence
Triboluminescence is a phenomenon in which light is generated when a material is mechanically pulled apart, ripped, scratched, crushed, or rubbed (see tribology). The phenomenon is not fully understood but appears in most cases to be caused by the separation and reunification of static electric charges, see also triboelectric effect. The term comes from the Greek τρίβειν ("to rub"; see tribology) and the Latin ''lumen'' (light). Triboluminescence can be observed when breaking sugar crystals and peeling adhesive tapes. ''Triboluminescence'' is often a synonym for ''fractoluminescence'' (a term mainly used when referring only to light emitted from fractured crystals). Triboluminescence differs from piezoluminescence in that a piezoluminescent material emits light when deformed, as opposed to broken. These are examples of mechanoluminescence, which is luminescence resulting from any mechanical action on a solid. History Quartz rattlers of the Uncompahgre Ute indigenous ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chemiluminescence
Chemiluminescence (also chemoluminescence) is the emission of light (luminescence) as the result of a chemical reaction, i.e. a chemical reaction results in a flash or glow of light. A standard example of chemiluminescence in the laboratory setting is the luminol test. Here, blood is indicated by luminescence upon contact with iron in hemoglobin. When chemiluminescence takes place in living organisms, the phenomenon is called bioluminescence. A light stick emits light by chemiluminescence. Physical description As in many chemical reactions, chemiluminescence starts with the combining of two compounds, say A and B, to give a product C. Unlike most chemical reactions, the product C converts to a further product, which is produced in an electronically excited state often indicated with an asterisk: : A + B → C : C → D* D* then emits a photon (''h''ν), to give the ground state of D: I : D* → D + ''h''ν In theory, one photon of light should be given off for each mol ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cathodoluminescence
Cathodoluminescence is an optical and electromagnetic phenomenon in which electrons impacting on a luminescent material such as a phosphor, cause the emission of photons which may have wavelengths in the visible spectrum. A familiar example is the generation of light by an electron beam scanning the phosphor-coated inner surface of the screen of a television that uses a cathode-ray tube. Cathodoluminescence is the inverse of the photoelectric effect, in which electron emission is induced by irradiation with photons. Origin Luminescence in a semiconductor results when an electron in the conduction band recombines with a hole in the valence band. The difference energy (band gap) of this transition can be emitted in form of a photon. The energy (color) of the photon, and the probability that a photon and not a phonon will be emitted, depends on the material, its purity, and the presence of defects. First, the electron has to be excited from the valence band into the con ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Photoluminescence
Photoluminescence (abbreviated as PL) is light emission from any form of matter after the absorption of photons (electromagnetic radiation). It is one of many forms of luminescence (light emission) and is initiated by photoexcitation (i.e. photons that excite electrons to a higher energy level in an atom), hence the prefix ''photo-''. Following excitation, various relaxation processes typically occur in which other photons are re-radiated. Time periods between absorption and emission may vary: ranging from short femtosecond-regime for emission involving free-carrier plasma in inorganic semiconductorsHayes, G.R.; Deveaud, B. (2002). "Is Luminescence from Quantum Wells Due to Excitons?". ''Physica Status Solidi A'' 190 (3): 637–640doi:10.1002/1521-396X(200204)190:33.0.CO;2-7/ref> up to milliseconds for phosphoresence processes in molecular systems; and under special circumstances delay of emission may even span to minutes or hours. Observation of photoluminescence at a certain ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Electrochemiluminescence
Electrochemiluminescence or electrogenerated chemiluminescence (ECL) is a kind of luminescence produced during electrochemical reactions in solutions. In electrogenerated chemiluminescence, electrochemically generated intermediates undergo a highly exergonic reaction to produce an electronically excited state that then emits light upon relaxation to a lower-level state. This wavelength of the emitted photon of light corresponds to the energy gap between these two states. ECL excitation can be caused by energetic electron transfer (redox) reactions of electrogenerated species. Such luminescence excitation is a form of chemiluminescence where one/all reactants are produced electrochemically on the electrodes. ECL is usually observed during application of potential (several volts) to electrodes of electrochemical cell that contains solution of luminescent species (polycyclic aromatic hydrocarbons, metal complexes, quantum dots or nanoparticles) in aprotic organic solvent (ECL compos ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Luminol
Luminol (C8H7N3O2) is a chemical that exhibits chemiluminescence, with a blue glow, when mixed with an appropriate oxidizing agent. Luminol is a white-to-pale-yellow Crystal, crystalline solid that is soluble in most polar organic solvents but insoluble in water. Forensic investigators use luminol to detect trace amounts of blood at crime scenes, as it reacts with the iron in hemoglobin. Biologists use it in cellular assays to detect copper, iron, and cyanides as well as specific proteins via western blotting. When luminol is sprayed evenly across an area, trace amounts of an activating oxidant make the luminol emit a blue glow that can be seen in a darkened room. The glow only lasts about 30 seconds but can be documented photographically. The glow is stronger in areas receiving more spray; the intensity of the glow does not indicate the amount of blood or other activator present. Synthesis Luminol is synthesized in a two-step process, beginning with 3-nitrophthalic acid. Fir ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fluorescence
Fluorescence is one of two kinds of photoluminescence, the emission of light by a substance that has absorbed light or other electromagnetic radiation. When exposed to ultraviolet radiation, many substances will glow (fluoresce) with colored visible light. The color of the light emitted depends on the chemical composition of the substance. Fluorescent materials generally cease to glow nearly immediately when the radiation source stops. This distinguishes them from the other type of light emission, phosphorescence. Phosphorescent materials continue to emit light for some time after the radiation stops. This difference in duration is a result of quantum spin effects. Fluorescence occurs when a photon from incoming radiation is absorbed by a molecule, exciting it to a higher energy level, followed by the emission of light as the molecule returns to a lower energy state. The emitted light may have a longer wavelength and, therefore, a lower photon energy than the absorbed radi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Candoluminescence
Candoluminescence is the light given off by certain materials at elevated temperatures (usually when exposed to a flame) that has an intensity at some wavelengths which can, through chemical action in flames, be higher than the blackbody emission expected from incandescence at the same temperature.H.F. Ivey, "Candoluminescence and radical-excited luminescence," ''Journal of Luminescence'' 8:4, pp. 271–307 (1974) The phenomenon is notable in certain transition-metal and rare-earth oxide materials (ceramics) such as zinc oxide, cerium(IV) oxide and thorium dioxide. History The existence of the candoluminescence phenomenon and the underlying mechanism have been the subject of extensive research and debate since the first reports of it in the 1800s. The topic was of particular interest before the introduction of electric lighting, when most artificial light was produced by fuel combustion. The main alternative explanation for candoluminescence is that it is simply "selective" ther ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Phosphor
A phosphor is a substance that exhibits the phenomenon of luminescence; it emits light when exposed to some type of radiant energy. The term is used both for fluorescent or phosphorescent substances which glow on exposure to ultraviolet or visible light, and cathodoluminescent substances which glow when struck by an electron beam ( cathode rays) in a cathode-ray tube. When a phosphor is exposed to radiation, the orbital electrons in its molecules are excited to a higher energy level; when they return to their former level they emit the energy as light of a certain color. Phosphors can be classified into two categories: fluorescent substances which emit the energy immediately and stop glowing when the exciting radiation is turned off, and phosphorescent substances which emit the energy after a delay, so they keep glowing after the radiation is turned off, decaying in brightness over a period of milliseconds to days. Fluorescent materials are used in applications in wh ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Radioluminescence
Radioluminescence is the phenomenon by which light is produced in a material by bombardment with ionizing radiation such as alpha particles, beta particles, or gamma rays. Radioluminescence is used as a low level light source for night illumination of instruments or signage. Radioluminescent paint is occasionally used for clock hands and instrument dials, enabling them to be read in the dark. Radioluminescence is also sometimes seen around high-power radiation sources, such as nuclear reactors and radioisotopes. Mechanism Radioluminescence occurs when an incoming particle of ionizing radiation collides with an atom or molecule, exciting an orbital electron to a higher energy level. The particle usually comes from the radioactive decay of an atom of a radioisotope, an isotope of an element which is radioactive. The electron then returns to its ground energy level by emitting the extra energy as a photon of light. A chemical that releases light of a particular color when ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
