Why luminol glows

Chemoluminescence spectroscopy is an important tool in chemical analysis. The emissions from excited molecules, either in the gas phase or in solution, are measured using a photomultiplier or similar light-sensitive instrument, possibly in combination with a chromatograph.

Measurement of the light emitted through chemoluminescence is used to determine the concentration of the excited chemical reagent. The efficiency with which light is emitted during luminescence is an important measure associated with chemoluminescence and bioluminescence. This number reveals the fraction of the energy used in the reaction that is emitted as light. A page from the "Causes of Color" exhibit A murderer can dispose of the victim's body and mop up the pools of blood , but without some heavy-duty cleaning chemicals, some evidence will remain.

Tiny particles of blood will cling to most surfaces for years and years, without anyone ever knowing they're there. The basic idea of luminol is to reveal these traces with a light-producing chemical reaction between several chemicals and hemoglobin , an oxygen-carrying protein in the blood.

The molecules break down and the atoms rearrange to form different molecules see Microsoft Encarta: Chemical Reaction for more information on chemical reactions. In this particular reaction, the reactants the original molecules have more energy than the products the resulting molecules.

The molecules get rid of the extra energy in the form of visible light photons. When a crime is committed that involves blood spilling, luminol can detect the blood even after cleaning, and even after a few years! So, how does luminol tell all? It is the main chemical C8H7O3N3 in a reaction that produces light. This powdery substance, made of carbon, hydrogen, oxygen, and nitrogen, is mixed with a liquid that contains hydrogen peroxide and a hydroxide, plus some other chemicals.

Investigators put this liquid into a spray bottle, and spray the area where they are looking for blood. To activate the lightstick, you bend the stick, which breaks the glass.

The chemicals mix, a reactions starts, and it produces light that makes the fluorescent dye glow. You can visit the chemistry section of About. The hydrogen peroxide oxidizes the phenyl oxalate ester to form phenol and an unstable peroxyacid ester. The unstable peroxyacid ester decomposes, resulting in phenol and a cyclic peroxy compound.

This compound decomposes to carbon dioxide. The decomposition reaction releases enough energy to excite the electrons in the fluorescent dye. The electrons jump to a higher energy level and then fall back down and release light. The decay of the excited state to a lower energy level is responsible for the emission of light. In , three chemists won the Nobel Prize in Chemistry for discovering and utilizing a protein that emits green light.

One of the important medical applications of fluorescent proteins is its use in the study of cancer.