Chemiluminescence Of “Luminol”

Chemiluminescence of “Luminol”

To exhibit its luminescence, the luminol must be activated with an oxidant. Usually, a solution containing hydrogen peroxide (H2O2) and hydroxide ions in water is used as the activator. In the presence of a catalyst such as an iron or periodate compound, the hydrogen peroxide is decomposed to form oxygen and water:

2H2O2 → O2 + 2 H2O

H2O2 + KIO4 → KIO3 + O2 + H2O

In a laboratory setting, the catalyst used is often potassium ferricyanide or potassium periodate. In the forensic detection of blood, the catalyst is the iron present in hemoglobin. Enzymes in a variety of biological systems may also catalyze the decomposition of hydrogen peroxide.

When luminol reacts with the hydroxide ion, a dianion is formed. The oxygen produced from the hydrogen peroxide then reacts with the luminol dianion. The product of this reaction, an organic peroxide, is very unstable and is made by the loss of a nitrogen, the change of electrons from excited state to ground state, and the emission of energy as a photon. This emission produces the blue glow. - Wiki

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