When working in crime, you need to use something to help find fingerprints, or excess blood stains, etc. That's where Luminol comes in, Luminol undergoes certain reactions to find blood in a crime scene.
Luminol reacts with the iron found in hemoglobin and causes it to discharge chemiluminescence. The reaction that triggers luminol's chemiluminescene has to be catalysed. The iron in blood can carry out this role, but it can also be oxidized by bleach to get the same effect.
What is Chemiluminescene?
Chemiluminescene is a property in which a substance undergoes a chemical reaction and releasin energy in a form of light. 2 chemicals reacts to form an excited intermidiate, which breaks down releasing some of it's energy as protons of light, to reach it's ground state.
What is Catalyst?
A catalyst is some material that speeds up chemical reactions. With a helping hand from a catalyst, molecules that might take years to interact can now do it in seconds.
Common Catalyst include
Biological: Copper and Cyanide & Labratory: Potassium Ferricyanide
Luminol must be activated by hydroxide salt forming a dianion. In the presence of iron, hydrogen peroxide decomposes to form oxygen
The picture above shows the decomposition of hydrogen peroxide in iron