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 Chemiluminescence |
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This name refers to a light emitting chemical reaction. Through this page, I will comment only the two most common reaction types known at this day. |
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The first one and probably the most famous has for major reactant the Luminol. Discovered by Huntress, Stanley and Parker in 1934, but it is only in 1942 that Weber showed its luminescence capability . And since this date, a lot of applications has been found for this organic molecule. |
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| Here is the mechanism of this reaction (thanks to http://fr.wikipedia.org/wiki/Luminol): | ||||
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With this scheme, we can see that light is emitted by the rearrangement of an instable peroxide obtained from the reaction with dioxygen. Therefore, many applications use hydrogen peroxide to provide oxygen. To make this one free to react, a catalyst such as a ferrous salt should be used to decompose hydrogen peroxide.
That is why luminol can be used in criminology, because of the presence of ferrous salt in blood.
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Luminol is used in several other applications such as biochemistry tests and analysis, cold light for security systems and also in education to make chemistry more attractive. |
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This type of reaction is known essentially with organic molecules, which have an oxalic-based structure. Dr. Edwin A. Chandross discovered the luminescence of this reaction in 1963 (a new chemiluminescent system. Tetrahedron Lett. 1963; 12: p761-765) |
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| Here is the mechanism of this reaction : | ||||
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We can see that the oxidative cleavage of the oxadione gives a phenolic compound and an intermediate structure called peroxyoxalate which is then decomposed into CO2 and we have at the same time an energy's transfer to the fluorophore compound. This back electron transfer gives an excited state to the structure and when this state comes back to a normal and stable state, this excess of energy is evacuated as light emitting. you can view here some of our fluorophores : and here for peroxyoxalate : |
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| The most simple structure that is able to give some light by this reaction way is oxalyl chloride. The little movie below shows you its reaction with the presence of a conjugated polymer which takes the fluorophore function: | ||||
In this movie, we add drop wise a solution of hydrogen peroxide into a THF solution containing MEH-PPV and oxalyl chloride. We can observe the formation of CO2 (bubble), which makes the solution move like a flame. Also, we can notice the disappearance of the red color given by the fluorophore, this can be simply explained by the fact that in addition to CO2, the reaction produces chlorine which adds itself on the conjugated polymer double bond and so, stops colored and fluorescence properties of the materials. Here is the secondary reaction that occurs in this experiment :
Need some of MEH-PPV ? click here ! |
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| Because of the excessive reactivity of Oxalyl chloride decomposition, this reaction is just used to make spectacular demonstration. | ||||
But chemiluminescence of peroxyoxalate can be used as needed, by changing solvent and reactive, as we did in this second movie. Here we took a bis-pentafluorophenyl peroxyoxalate and a fluorophore, which were both dissolved in dichloromethane and added drop by drop into a solution of hydrogen peroxide and potassium hydroxide. |
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Further more, this chemical reaction has a lot of applications, the first one being to make cold light, like light stick well known as Cyalum or snapstick. Because of the multi-reactants present in the reactional mechanism, we can shape the effect needed like the light color and the duration as we can see in this movie below : |
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You can purchase several of these reactants by visiting our products page just by clicking here |
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Cold lights are used for several purposes such as scuba diving, emergency beacons and also where heat or flames are prohibited like in laboratories which make explosives. This kind of chemiluminescence is also used in analytical chemistry by using spectrometer and other apparatus for the determination of some organic compound, hydrogen peroxide and others. It is common to use Imidazol like Lophine as emissive molecule to make analysis of metals. You can also buy this kind of molecule by clicking here 
on top of it, they have several other applications especially in medicine. |
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