Glow stick
A glow stick, also known as a light stick, chem light, light wand, light rod, and rave light, is a self-contained, short-term light-source. It consists of a translucent plastic tube containing isolated substances that, when combined, make light through chemiluminescence. The light cannot be turned off and can be used only once. The used tube is then thrown away. Glow sticks are often used for recreation, such as for events, camping, outdoor exploration, and concerts. Glow sticks are also relied upon for light during military, police, fire, and emergency medical services operations. Industrial uses  include marine, transportation, and mining. History. Bis(2,4,5-trichlorophenyl-6-carbopentoxyphenyl)oxalate, trademarked "Cyalume", was invented in 1971 by Michael M. Rauhut, Laszlo J. Bollyky, and Robert W. Sombathy of American Cyanamid, based on work by Edwin A. Chandross of Bell Labs. Other early work on chemiluminescence was carried out at the same time, by researchers under Herbert Richter at China Lake Naval Weapons Center. Several US patents for glow stick-type devices were received by various inventors. Bernard Dubrow and Eugene Daniel Guth patented a packaged chemiluminescent material in June 1965. In October 1973, Clarence W. Gilliam, David Iba Sr., and Thomas  N. Hall were registered as inventors of the Chemical Lighting Device. In June 1974, a patent for a Chemiluminescent Device was issued with Herbert P. Richter and Ruth E. Tedrick listed as the inventors. In January 1976, a patent was issued for the Chemiluminescent Signal Device, with Vincent J. Esposito, Steven M. Little, and John H. Lyons listed as the inventors. This patent recommended a single glass ampoule that is suspended in a second substance, that when broken and mixed together, provide the chemiluminescent light. The design also included a stand for the signal device so it could be thrown  from a moving vehicle and remain standing in an upright position on the road. The idea was this would replace traditional emergency roadside flares and would be superior, since it was not a fire hazard, would be easier and safer to deploy, and would not be made ineffective if struck by passing vehicles. This design, with its single glass ampoule inside a plastic tube filled with a second substance that when bent breaks the glass and then is shaken to mix the substances, most closely resembles the typical glow stick sold today. In December 1977, a patent was issued for  a Chemical Light Device with Richard Taylor Van Zandt as the inventor. This design alteration features a steel ball which shatters the glass ampoule when the glow stick is exposed to a predetermined level of shock; an example is an arrow flown dark but illuminating its landing location upon sudden deceleration. In the early 1980s the majority of glow sticks were produced in Novato, California by Omniglow Corp. Omniglow completed a leveraged buyout of American Cyanamid's chemical light division in 1994 and became the leading supplier of glow sticks worldwide until going out of business in 2014. Most glow  sticks seen today are now made in China. Uses. Glow sticks are waterproof, do not use batteries, generate negligible heat, are inexpensive, and are reasonably disposable. They can tolerate high pressures, such as those found under water. They are used as light sources and light markers by military forces, campers, and recreational divers. Entertainment. Glowsticking is the use of glow sticks in dancing. They are frequently used for entertainment at parties (in particular raves), concerts, and dance clubs. They are used by marching band conductors for evening performances; glow sticks are also used in festivals and celebrations around the world . Glow sticks also serve multiple functions as toys, readily visible night-time warnings to motorists, and luminous markings that enable parents to keep track of their children. Another use is for balloon-carried light effects. Glow sticks are also used to create special effects in low light photography and film. The "Guinness Book of Records" recorded the world's largest glow stick was cracked at tall. It was created by the University of Wisconsin–Whitewater's Chemistry Department to celebrate the school's sesquicentennial, or 150th birthday in Whitewater, Wisconsin and cracked on 9 September 2018. Recreation and survival. Glow  sticks are used for outdoor recreation, often used at night for marking. Scuba divers use diving-rated glow sticks to mark themselves during night dives, and then can turn off bright diving lights. This is done to enable visibility of bioluminescent marine organisms, which cannot be seen while a bright dive light is illuminated. Similarly, glow sticks are used on backpacks, tent pegs, and on jackets during overnight camping expeditions. Often, glow sticks are recommended as an addition to survival kits. Industry. There are specific industrial uses of glow sticks, which are often used as a light source in  circumstances where electric lighting and LED's are not best suited. For example, in the mining industry, glow sticks are required for emergency evacuation in the case of a gas leak. Use of an electric light source in this case may cause an unintended explosion. Chemiluminescence, the type of light used in glow sticks, is a "cold-light" and does not use electricity, and will not cause a gas leak to ignite. Glow sticks are also used worldwide in the marine industry, often used as fishing lures in long-line, recreational, and commercial fishing, as well as for personnel safety . Military. Glow sticks are used by militaries, and occasionally also police tactical units, to mark cleared rooms or objects of note while clearing buildings during close-quarters combat. They are also used to help identify friendly soldiers during nighttime operations. Emergency services. Glow sticks are used by emergency services as back-up light sources. For example, glow sticks are part of the UN's emergency relief kits to people experiencing natural and humanitarian disasters. Often, emergency rescue crews will hand out glow sticks in order to keep track of people at night, who may not have access to their own  lighting. Glow sticks are sometimes attached to life vests and lifeboats on passenger and commercial vessels, to ensure night time visibility. Glow stick emergency lighting stations are sometimes available for public transportation, such as subways, for emergency light to get passengers to safety in case of an emergency. Operation. Glow sticks emit light when two chemicals are mixed. The reaction between the two chemicals is catalyzed by a base, usually sodium salicylate. The sticks consist of a tiny, brittle container within a flexible outer container. Each container holds a different solution. When the outer container is flexed, the inner container  breaks, allowing the solutions to combine, causing the necessary chemical reaction. After breaking, the tube is shaken to thoroughly mix the components. The glow stick contains two chemicals, a base catalyst, and a suitable dye (sensitizer, or fluorophor). This creates an exergonic reaction. The chemicals inside the plastic tube are a mixture of the dye, the base catalyst, and diphenyl oxalate. The chemical in the glass vial is hydrogen peroxide. By mixing the peroxide with the phenyl oxalate ester, a chemical reaction takes place, yielding two moles of phenol and one mole of peroxyacid ester (1,2-dioxetanedione). The peroxyacid decomposes  spontaneously to carbon dioxide, releasing energy that excites the dye, which then relaxes by releasing a photon. The wavelength of the photon—the color of the emitted light—depends on the structure of the dye. The reaction releases energy mostly as light, with very little heat. The reason for this is that the reverse [2 + 2] photocycloadditions of 1,2-dioxetanedione is a forbidden transition (it violates Woodward–Hoffmann rules) and cannot proceed through a regular thermal mechanism. By adjusting the concentrations of the two chemicals and the base, manufacturers can produce glow sticks that glow either brightly for  a short amount of time or more dimly for an extended length of time. This also allows glow sticks to perform satisfactorily in hot or cold climates, by compensating for the temperature dependence of reaction. At maximum concentration (typically found only in laboratory settings), mixing the chemicals results in a furious reaction, producing large amounts of light for only a few seconds. The same effect can be achieved by adding copious amounts of sodium salicylate or other bases. Heating a glow stick also causes the reaction to proceed faster and the glow stick to glow more brightly for a brief  period. Cooling a glow stick slows the reaction a small amount and causes it to last longer, but the light is dimmer. This can be demonstrated by refrigerating or freezing an active glow stick; when it warms up again, it will resume glowing. The dyes used in glow sticks usually exhibit fluorescence when exposed to ultraviolet radiation—even a spent glow stick may therefore shine under a black light. The light intensity is high immediately after activation, then exponentially decays. Leveling of this initial high output is possible by refrigerating the glow stick before activation. A combination of two fluorophores  can be used, with one in the solution and another incorporated to the walls of the container. This is advantageous when the second fluorophore would degrade in solution or be attacked by the chemicals. The emission spectrum of the first fluorophore and the absorption spectrum of the second one have to largely overlap, and the first one has to emit at shorter wavelength than the second one. A downconversion from ultraviolet to visible is possible, as is conversion between visible wavelengths (e.g., green to orange) or visible to near-infrared. The shift can be as much as 200 nm, but  usually the range is about 20–100 nm longer than the absorption spectrum. Glow sticks using this approach tend to have colored containers, due to the dye embedded in the plastic. Infrared glow sticks may appear dark-red to black, as the dyes absorb the visible light produced inside the container and reemit near-infrared. On the other hand, various colors can also be achieved by simply mixing several fluorophores within the solution to achieve the desired effect. These various colors can be achieved due to the principles of additive color. For example, a combination of red, yellow, and green fluorophores  is used in orange light sticks, and a combination of several fluorescers is used in white light sticks. Safety issues. Toxicity. In glow sticks, phenol is produced as a byproduct. It is advisable to keep the mixture away from skin and to prevent accidental ingestion if the glow stick case splits or breaks. If spilled on skin, the chemicals could cause slight skin irritation, swelling, or, in extreme circumstances, vomiting and nausea. Some of the chemicals used in older glow sticks were thought to be potential carcinogens. The sensitizers used are polynuclear aromatic hydrocarbons, a class of compounds known for  their carcinogenic properties. Dibutyl phthalate, an ingredient sometimes used in glow sticks, has raised some health concerns. It was put on California's list of suspected teratogens in 2006. Glow sticks contain ingredients that act as a plasticizer. This means if a glow stick leaks onto anything plastic it can liquefy it. Diphenyl oxalate can sting and burn eyes, irritate and sting skin and can burn the mouth and throat if ingested. Additionally, used glow sticks that remain in the environment cause long term pollution. This Nature Paper outlines the many secondary reactions that continue to react within the used  glow sticks and chem lights used by the marine industry (and is similar for all glow stick types). "Loss of viability, cell cycle changes and DNA fragmentation were observed in HepG2 cell line and skin fibroblasts. A non-cytotoxic LS (Light Stick) concentration increased the occurrence of the mutagenic lesion 1,"N"6-εdAdo in HepG2 DNA by three-fold. Additionally, in vitro incubations of spent LS contents with DNA generated dGuo-LS adducts, whose structure elucidation revealed the presence of a reactive chlorinated product. In conclusion, the LS contents were found to be highly cyto- and genotoxic. Our data indicate an  urgent need for LS waste management guidelines and for adequate information regarding toxic outcomes that may arise from human exposure." Single-use plastics. Glow sticks also contribute to the plastic waste problem, as glow sticks are single-use and made from plastic. Additionally, since the inner vial is often made from glass and the chemicals inside are dangerous if improperly handled, the plastic used for glow sticks is non-recoverable by recycling services, so glow sticks are categorized as non-recyclable waste. Safety improvements. By the 2020s, work was being done to create safer glow sticks and alternatives. Canadian company  Nyoka Design Labs develops glow stick alternatives. The Light Wand is biodegradable and glows with bioluminescence, rather than the chemiluminescence. The LUMI is a reusable and non-toxic alternative that glows with phosphorescence, and is chemically and biologically inert.