Glow Sticks!

A glow stick is a self-contained, short-term light-source. It consists of a translucent plastic tube containing isolated substances that, when combined, make light through chemiluminescence, so it does not require an external energy source. The light cannot be turned off, and can be used only once. Glow sticks are often used for recreation, but may also be relied upon for light during military, police, fire, or Emergency operations.



Chemistry of Glow Stick Colours

A glow stick contains two chemicals and a suitable dye. The chemicals inside the plastic tube are a mixture of the dye and diphenyl oxalate. The chemical in the glass vial is hydrogen peroxide. By mixing the peroxide with the phenyl oxalate ester, a chemical reaction takes place, yielding two molecules of phenol and one molecule of peroxyacid ester (1,2-dioxetanedione). The peroxyacid decomposes spontaneously to carbon dioxide, releasing energy that excites the dye, which then relaxes by releasing a photon. The wavelength of the photon—the color of the emitted light—depends on the structure of the dye.

As stated by the excellent article by Compound Interest, a range of different chemicals can be used, including those shown above, as well as one or two additional dyes. Whilst the molecules of the dye are always present in the solution, the hydrogen peroxide and the diphenyl oxalate are slowly used up by the reaction, until one runs out and the reaction ceases – and it’s at this point that the glow stick will stop emitting its glow.