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Luminescence
Luminescence is spontaneous emission of light by a substance not resulting from heat; or "cold light". It is thus a form of cold-body radiation. It can be caused by chemical reactions, electrical energy, subatomic motions or stress on a crystal. This distinguishes luminescence from incandescence, which is light emitted by a substance as a result of heating. Historically, radioactivity was thought of as a form of "radio-luminescence", although it is today considered to be separate since it involves more than electromagnetic radiation. 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 The following are types of luminescence: * Chemiluminescence, the emission of light as a result of a chemical reaction ** Bioluminescence, a result of biochemical reactions in a living organism **Electrochemiluminescence, a result of an electrochemical reaction **Lyolum ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bioluminescence
Bioluminescence is the production and emission of light by living organisms. It is a form of chemiluminescence. Bioluminescence occurs widely in marine vertebrates and invertebrates, as well as in some fungi, microorganisms including some bioluminescent bacteria, and terrestrial arthropods such as fireflies. In some animals, the light is bacteriogenic, produced by symbiotic bacteria such as those from the genus '' Vibrio''; in others, it is autogenic, produced by the animals themselves. In a general sense, the principal chemical reaction in bioluminescence involves a light-emitting molecule and an enzyme, generally called luciferin and luciferase, respectively. Because these are generic names, luciferins and luciferases are often distinguished by the species or group, e.g. firefly luciferin. In all characterized cases, the enzyme catalyzes the oxidation of the luciferin. In some species, the luciferase requires other cofactors, such as calcium or magnesium ions, and so ... [...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. History The sonoluminescence effect was first discovered at the University of Cologne in 1934 as a result of work on sonar. Hermann Frenzel and H. Schultes put an ultrasound transducer in a tank of photographic developer fluid. They hoped to speed up the development process. Instead, they noticed tiny dots on the film after developing and realized that the bubbles in the fluid were emitting light with the ultrasound turned on. It was too difficult to analyze the effect in early experiments because of the complex environment of a large number of short-lived bubbles. This phenomenon is now referred to as multi-bubble sonoluminescence (MBSL). In 1960, Peter Jarman from Imperial College of London proposed the most reliable theory of sonoluminescence phenomenon. He concluded that sonoluminescence is basically thermal in origin and that it might possibly arise from microshocks wi ... [...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 to be caused by the separation and reunification of static electrical charges. 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 used as a synonym for ''fractoluminescence'' (a term sometimes used when referring only to light emitted from fractured crystals). Triboluminescence differs from piezoluminescence in that a piezoluminescent material emits light when it is deformed, as opposed to broken. These are examples of mechanoluminescence, which is luminescence resulting from any mechanical action on a solid. History Uncompahgre Ute indigenous people The Uncompahgre Ute indigenous p ... [...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. There may also be limited emission of heat. Given reactants A and B, with an excited intermediate ◊, : + -> lozenge -> roducts+ light For example, if is luminol and is hydrogen peroxide in the presence of a suitable catalyst we have: :\underset + \underset -> 3-APAlozenge-> + light where: * 3-APA is 3-aminophthalate * 3-APA ''◊is the vibronic excited state fluorescing as it decays to a lower energy level. General description The decay of this excited state ''◊to a lower energy level causes light emission. In theory, one photon of light should be given off for each molecule of reactant. This is equivalent to the Avogadro number of photons per mole of reactant. In actual practice, non-enzymatic reactions seldom exceed 1% QC, quantum efficiency. In a chemical reaction, reactants collide to form a transition state, the enthalpic maximum in ... [...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 condu ... [...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 e ... [...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 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, 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. First ... [...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 compo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fluorescence
Fluorescence is the emission of light by a substance that has absorbed light or other electromagnetic radiation. It is a form of luminescence. In most cases, the emitted light has a longer wavelength, and therefore a lower photon energy, than the absorbed radiation. A perceptible example of fluorescence occurs when the absorbed radiation is in the ultraviolet region of the electromagnetic spectrum (invisible to the human eye), while the emitted light is in the visible spectrum, visible region; this gives the fluorescent substance a distinct color that can only be seen when the substance has been exposed to blacklight, UV light. Fluorescent materials cease to glow nearly immediately when the radiation source stops, unlike phosphorescence, phosphorescent materials, which continue to emit light for some time after. Fluorescence has many practical applications, including mineralogy, gemology, medicine, chemical sensors (fluorescence spectroscopy), fluorescent labelling, dyes, bio ... [...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" thermal ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Phosphorescence
Phosphorescence is a type of photoluminescence related to fluorescence. When exposed to light (radiation) of a shorter wavelength, a phosphorescent substance will glow, absorbing the light and reemitting it at a longer wavelength. Unlike fluorescence, a phosphorescent material does not immediately reemit the radiation it absorbs. Instead, a phosphorescent material absorbs some of the radiation energy and reemits it for a much longer time after the radiation source is removed. In a general sense, there is no distinct boundary between the emission times of fluorescence and phosphorescence (i.e.: if a substance glows under a black light it is generally considered fluorescent, and if it glows in the dark it is often simply called phosphorescent). In a modern, scientific sense, the phenomena can usually be classified by the three different mechanisms that produce the light, and the typical timescales during which those mechanisms emit light. Whereas fluorescent materials stop emit ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Piezoluminescence
Piezoluminescence is a form of luminescence created by pressure upon certain solids. This phenomenon is characterized by recombination processes involving electrons, holes and impurity ion centres. Some piezoelectric crystals give off a certain amount of piezoluminescence when under pressure. Irradiated salts, such as NaCl, KCl, KBr and polycrystalline chips of LiF (TLD-100), have been found to exhibit piezoluminescent properties. It has also been discovered that ferroelectric polymers exhibit piezoluminescence upon the application of stress. In the folk-literature surrounding psychedelic production, DMT, 5-MeO-DMT, and LSD have been reported to exhibit piezoluminescence. As specifically noted in the book '' Acid Dreams'', it is stated that Augustus Owsley Stanley III, one of the most prolific producers of LSD in the 1960s, observed piezoluminescence in the compound's purest form, which observation is confirmed by Alexander Shulgin: "A totally pure salt, when dry and when shaken ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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