Chemistry

What Chemicals cause Glow Sticks to Glow and how they Work



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Around many discos and parties, the multicolored glow sticks have become a very familiar sight. These fun items utilize the property of chemiluminescence to produce their light.

To get a glow stick to work a person has to break a thin walled fragile tube contained within the flexible outer tube. This allows the chemicals within the inner tuber to react with the chemical surrounding it.

These two chemicals within the inner tube are diphenyl oxalate and a dye and surrounding these is hydrogen peroxide. When diphenyl oxalate reacts with the hydrogen peroxide, it produces phenol and peroxyacid ester. The peroxyacid is unstable and decomposes to carbon dioxide. The production of carbon dioxide release energy, which in turn excites the dye molecules. As the dye molecules relax, they release this energy in the form of photons so causing the glow stick to light up.

The contents of a glow stick may be hazardous to health and should not be applied to the skin. Hydrogen peroxide and phenol are both irritants and in extreme reactions may cause tissue swelling, nausea and vomiting. Some of the dyes may be potential carcinogens.

The length of time an activated glow stick will shine and its brightness depends on both the concentrations of the reactants and the temperature of its usage. At higher temperatures, the chemical reaction is faster, so the stick will emit a brighter light but for a shorter time. At low temperatures with a slower reaction time, the dim light produced will last a longer time. The kinetics of the reaction causes the stick to be brighter immediately after the breaking of the inner vial and then to start to fade. If a stick is refrigerated prior to activation, the stick will emit a more even level of light during the reaction.

The color of the glow stick will depend on the dye contained within the inner tube. There are many dyes, also known as fluorophors, used in glow sticks. These dyes include 5,12-bis(phenylethynyl)naphthacene (orange light), 9,10-diphenylanthracene or DPA (blue light) and 1,8-dichloro-9,10-bis(phenylethynyl)anthracene (yellow light). Theses dyes are fluorescent, hence fluorophor, and will emit visible light if illuminated with the ultra violet radiation produced by a “black light”.

In addition to adding entertainment to parties glow sticks have a number of valuable uses. In disaster zones they provide a safe source of light without the need of batteries or causing any sparks. The use of fluorophors that emit infrared radiation, such as 6-methylacridinium iodide, allows them to be used with specialized night vision equipment. Campers, military, law enforcement personnel and many others use them for illumination.




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