Chemiluminescence Reactions
– The decay of excited states causes light emission.
– In theory, one photon of light is given off for each molecule of reactant.
– Non-enzymatic reactions seldom exceed 1% quantum efficiency.
– Reactants collide to form a transition state in a chemical reaction.
– Exothermic reactions make their solutions hotter by dispersing vibrational energy.
– Chemiluminescence in aqueous systems is mainly caused by redox reactions.
– Luminol in an alkaline solution with hydrogen peroxide produces chemiluminescence.
– Iron or copper, or an auxiliary oxidant, can also induce chemiluminescence.
– The luminol reaction can be represented as: luminol + hydrogen peroxide -> 3-APA + light.
– Chemiluminescence in liquid-phase reactions is commonly used in the luminol test for blood detection.
– Elemental white phosphorus oxidizing in moist air produces a green glow.
– Nitric oxide detection in environmental air-quality testing is based on a gas-phase reaction.
– Ozone combined with nitric oxide forms nitrogen dioxide in an activated state.
– The activated nitrogen dioxide luminesces as it reverts to a lower energy state.
– Photons emitted during the reaction are proportional to the amount of nitric oxide present.
– Infrared chemiluminescence refers to the emission of infrared photons from vibrationally excited product molecules.
– The intensities of infrared emission lines are used to measure the populations of vibrational states.
– IRCL was developed as a kinetic technique by John Polanyi.
– IRCL is more intense for reactions with an attractive potential energy surface.
– Reactions with a repulsive potential energy surface lead to little IRCL.
– Enhanced chemiluminescence (ECL) is commonly used for detection assays in biology.
– ECL involves the conversion of an enhanced chemiluminescent substrate into a sensitized reagent.
– The sensitized reagent emits light when it decays to the singlet carbonyl state.
– ECL allows detection of minute quantities of biomolecules.
– Proteins can be detected down to femtomole quantities using ECL.
Applications of Chemiluminescence
– Chemiluminescence is used in biomedical research for imaging and testing drugs in the pre-clinical stages.
– It is effective in evaluating the effectiveness of cancer drugs that target a tumor’s blood supply.
– Chemiluminescence can be used in molecular biology to assess calcium levels in cells.
– The reaction of chemiluminescence requires the energy source adenosine triphosphate (ATP).
– Different species produce luminescence using molecules called luciferin.
Bioluminescence in Nature
– Many organisms have evolved to produce light for various purposes, such as luring prey, camouflage, or attracting mates.
– Deep sea organisms emit blue and green light, which can transmit more easily in water.
– Some bacteria use bioluminescence for communication.
– The difference in color of bioluminescent light is due to the degree of conjugation of the molecule at the molecular level.
– Bioluminescent plants have been genetically engineered using genes from bioluminescent mushrooms.
Chemiluminescence vs. Fluorescence
– Chemiluminescence is different from fluorescence.
– Fluorescent proteins like Green fluorescent protein are not chemiluminescent.
– Combining GFP with luciferases allows for bioluminescence resonance energy transfer (BRET), increasing the quantum yield of light emitted.
– Chemiluminescence and fluorescence have different mechanisms of light emission.
– Chemiluminescent reactions can be more sensitive and have lower background noise compared to fluorescence.
Related Concepts and References
– Eclox, a chemiluminescent compound used in analytical chemistry.
– Electrochemiluminescence, a process that combines electrochemistry and chemiluminescence.
– List of light sources, providing information on various sources of light.
– Lyoluminescence, a phenomenon where solid materials emit light when dissolved in a liquid.
– Will-o-the-wisp, a natural phenomenon of atmospheric ghost lights.
– References: Vacher, Morgane et al. (2018). Chemi- and Bioluminescence of Cyclic Peroxides. Chemical Reviews, 118(15), 6927-6974. Radziszewski, B. R. (1877). Untersuchungen über Hydrobenzamid, Amarin und Lophin. Berichte der Deutschen Chemischen Gesellschaft, 10(1), 70-75. Shah, Syed Niaz Ali and Lin, Jin-Ming (2017). Recent advances in chemiluminescence based on carbonaceous dots. Advances in Colloid and Interface Science, 241, 24-36. Luminol chemistry laboratory demonstration. Retrieved 2006-03-29. Kuntzleman, Thomas Scott et al. (2012). The Chemistry of Lightsticks: Demonstrations To Illustrate Chemical Processes. Journal of Chemical Education, 89(7), 910-916. Source: https://en.wikipedia.org/wiki/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 ◊,
![{\displaystyle {\ce {[A]{}+[B]->{}[\lozenge ]{}->{}[products]{}+light}}}](https://wikimedia.org/api/rest_v1/media/math/render/svg/182aa07705ed2d88c916ecb96df96ab7c51a8818)
For example, if [A] is luminol and [B] is hydrogen peroxide in the presence of a suitable catalyst we have:
![{\displaystyle {\ce {{\underset {luminol}{C8H7N3O2}}+{\underset {hydrogen\ peroxide}{H2O2}}->3-APA[\lozenge ]->{3-APA}+light}}}](https://wikimedia.org/api/rest_v1/media/math/render/svg/e4cbbb6ca43888cca92605acd2bb5c8db9e2ee3d)
where:
- 3-APA is 3-aminophthalate
- 3-APA[◊] is the vibronic excited state fluorescing as it decays to a lower energy level.
