Chemiluminescence

In the chemiluminescence ( English: chemiluminescence ) or chemiluminescence mentioned phenomenon, is a process in which a chemical reaction electromagnetic radiation is emitted in the visible light region. If the luminescence of the term is held in the infrared region used infrared chemiluminescence.

Bioluminescence is a special case of the chemiluminescence in biological systems.

Discovery

As early as 1000 BC first theses about bioluminescent creatures have been described in China. The first chemiluminescent reaction was already in 1669 by Hamburg alchemist Hennig Brand Heinrich discovered by accident ( Phosphorus Mirabilis, lights of phosphorus vapors when oxidized by atmospheric oxygen or water). He suspected that there is in human urine gold, whereupon he eindampfte few thousand liters and reduced with coal. Here, the present in the urine phosphate was reduced to phosphorus and stimulated by subsequent oxidation to shine. Eilhard Wiedemann coined in 1888 the term " chemiluminescence ".

Basis

The emission of light in the chemiluminescence is a consequence of the transition of an electron from an excited state to an energetically lower-lying state, possibly the ground state. Unlike the fluorescence and phosphorescence of the excited state is achieved in the chemiluminescence by a chemical reaction.

Starting materials for chemiluminescent reactions are referred to as luminophores. The most popular is 3-amino- phthalic hydrazide ( luminol ). Under peroxyoxalate chemiluminescence refers to reactions of hydrogen peroxide with derivatives of oxalic acid in the presence of sensitizers. Many luminophores are 1,2 - or 1,4- dicarbonyl compounds such as oxalic acid esters (such as diphenyl and derivatives thereof ), and luminol.

3- aminophthalhydrazide ( luminol ), a 1,4- dicarbonyl compound

In most chemiluminescent reactions is first produced an unstable intermediate with a peroxide bridge, the high-energy decay products a charge transfer complex with a dye molecule ( sensitizer [dt. Sensitiser ], a molecule with a plurality of double or triple bonds) is received, and transfers energy to it. The excited dye molecule then emits a photon whose wavelength depends on the structure of the dye used.

Under certain conditions, can also generate an oscillating chemiluminescence, such as by combining the Orban oscillator with luminol.

Applications

The most well-known chemiluminescent reaction is the oxidation of luminol by hydrogen peroxide in the presence of iron or manganese ions, which is used in forensics for the visualization of traces of blood ( the blood pigment hemoglobin contains Fe2 ions). The oxidized luminol molecule serves simultaneously as a sensitizer.

Are commercially available, plastic tubes that give off when folded ( Starlights ) an intense, different -colored, long-lasting light. This light will be produced by chemiluminescence. In the tube there are three chemical components: an oxalic ester, a dye whose emission determines the color of light, and a glass tube with hydrogen peroxide. If the tube is broken with hydrogen peroxide starts peroxyoxalate chemiluminescence.

The chemiluminescence of 1,2-dioxetanes is in biochemistry and medical diagnostics application. Through it one is able to reliably detect the smallest traces of enzymes down to individual molecules. Among other luminophores, such as luminol, acridinium ester or luciferins the concentrations of antibodies and antigens are determined in the chemiluminescence immunoassay so. In addition, ATP and NADH can be determined to very low concentrations in biological media. For many substrates which are associated with ATP -sensitive detection systems have been developed.