Glow Sticks - How they work...

Glow Sticks... What exactly are they you ask? Well I guess this can be answered in a couple different ways. The best way to start is probably with the simplest explanation...

Glow sticks, aka Light sticks, are simply transparent plastic tubes which contain 2 chemical liquids held apart in different compartments. One compartment is a plastic tube and the other compartment is a small glass tube inside. When you bend the plastic tube the small glass tube inside breaks and in doing so lets the two chemicals mix. Once the 2 liquids mix there is a chemical reaction which creates light. This phenomenon is called chemiluminescence.

Now, the second explanation is a little more complex and I don't know about you but just trying to get my head around it hurts my brain...but here goes...

Glow stick Chemistry

The Glowstick, aka light stick, contains two chemicals and a suitable fluorescent dye (sensitizer, or fluorophor). The chemicals in the plastic tube are a mixture of the dye and a derivate of phenyl oxalate etser (also called Cyalume). The chemical inside the glass tube is concentrated (about 35%) hydrogen peroxide. By mixing the peroxide with the phenyl oxalate ester, a chemical reaction takes place; the ester is oxidized, yielding two molecules of phenol and one molecule of peroxyacid ester. The peroxyacid decomposes spontaneously to carbon dioxide, releasing energy that excites the dye, which then deexcites by releasing a photon. The wavelength of the photon depends on the structure of the dye; eg. 9,10-bis(phenylethynyl)anthracene gives green light, 9,10-diphenylanthracene gives blue light, 5,6,11,12-tetraphenylnaphthacene gives red light. Other colours can be made of combination of dyes, eg. Purple requires three dyes.

Other chemicals are usually present in the mixture as well; eg. sodium salicylate as a catalyst, and Bis(2-ethylhexyl) phthalate (DEHP) as a solvent.

Instead of bis(phenyl)oxalate, bis(2,4,5-trichlorophenyl-6-carbopentoxyphenyl)oxalate (CPPO) is used in practical formulations, as it gives significantly better quantum yield.

A similar reaction can be achieved with bis(2,4,6-trichlorophenyl)oxalate (TCPO).

The dyes used in Glowsticks (lightsticks) usually exhibit fluorescence when exposed to ultraviolet radiation. Therefore even a spent glow stick (lightstick) will shine under a black light.

Fluorophors used

• 9,10-diphenylanthracene (DPA) emits blue light. 
•  1-chloro-9,10-diphenylanthracene (1-chloro(DPA)) and 1-chloro-9,10-diphenylanthracene (2-chloro(DPA)) emit blue-green light with higher efficiency than unsubstituted DPA, dihydro(DPA) is purple.
• 9,10-bis(phenylethynyl)anthracene (BPEA) emits green light
• 1-chloro-9,10-bis(phenylethynyl)anthracene emits yellow-green light. 
•  2-chloro-9,10-bis(phenylethynyl)anthracene emits green light.
• 1,8-dichloro-9,10-bis(phenylethynyl)anthracene emits yellow light.
• Rubrene emits orange-red light.
• 2,4-di-tert-butylphenyl 1,4,5,8-tetracarboxynaphthalene diamide emits deep red light, together with DPA is used to produce white or hot-pink light, depending on their ratio.

Some information gathered from http://en.wikipedia.org/wiki/Glow_sticks