Luminol is a white-to-pale-yellow crystalline solid that is soluble in most polar organic solvents but insoluble in water. It exhibits chemiluminescence with a blue glow when mixed with an appropriate oxidizing agent. 

Mechanisms

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 the activator. In the presence of a catalyst such as an iron or periodate compound, the hydrogen peroxide decomposes to form oxygen and water:

2 H2O2 → O2 + 2 H2O

H2O2 + KIO4 → KIO3 + O2 + H2O

Laboratory settings often use potassium ferricyanide or potassium periodate for the catalyst. In the forensic detection of blood, the catalyst is the iron present in hemoglobin.^[1]

Uses

Luminol (5-aminophthalylhydrazide) is so far the most frequently used CL reagent. The CL emission of luminol is based on its oxidation by hydrogen peroxide, hexacyanoferrate(III), permanganate, N-bromosuccinimide (or N-chlorosuccinimide), periodate, dichromate, persulphate, dichlorocyanurate or trichlorocyanuric acid, chlorate and electrogenerated hypobromite in alkaline medium.

Methods

Luminol is synthesized in a two-step process, beginning with 3-nitrophthalic acid.First, hydrazine (N2H4) is heated with the 3-nitrophthalic acid in a high-boiling solvent such as triethylene glycol and glycerol. A condensation reaction occurs, with loss of water, forming 3-nitrophthalhydrazide. Reduction of the nitro group to an amino group with sodium dithionite (Na2S2O4), via a transient hydroxylamine intermediate, produces luminol.

References

[1] Ples, Marek. "Chemiluminescence activated by blood". www.weirdscience.eu (in Polish). Archived from the original on 3 January 2015. Retrieved 23 December 2014.