How Glow Stick Colors Work

Colourful glow sticks

Steve Passlow / Getty Images

A glow stick is a light source based on chemiluminescence. Snapping the stick breaks an inner container filled with hydrogen peroxide. The peroxide mixes with diphenyl oxalate and a fluorophor. All glow sticks would be the same color, except for the fluorophor. Here's a closer look at the chemical reaction and how different colors are produced.

Key Takeaways: How Glowstick Colors Work

  • A glowstick or lightstick works via chemiluminescence. In other words, a chemical reaction generates the energy used to produce light.
  • The reaction is not reversible. Once the chemicals are mixed, the reaction proceeds until no more light is produced.
  • A typical glowstick is a translucent plastic tube that contains a small, brittle tube. When the stick is snapped, the inner tube breaks and allows two sets of chemicals to mix.
  • The chemicals include diphenyl oxalate, hydrogen peroxide, and a dye that produces different colors.

Glow Stick Chemical Reaction

The Cyalume reaction produces the colored light seen in glow sticks.

Smurrayinchester / Wikimedia Commons / CC BY-SA 3.0 

There are several chemiluminescent chemical reactions that may be used to produce light in glow sticks, but the luminol and oxalate reactions are commonly used. American Cyanamid's Cyalume light sticks are based on the reaction of bis(2,4,5-trichlorophenyl-6-carbopentoxyphenyl)oxalate (CPPO) with hydrogen peroxide. A similar reaction occurs with bis(2,4,6-trichlorophenyl)oxlate (TCPO) with hydrogen peroxide.

An endothermic chemical reaction occurs. Peroxide and phenyl oxalate ester react to yield two moles of phenol and one mole of peroxyacid ester, which decomposes into carbon dioxide. The energy from the decomposition reaction excites the fluorescent dye, which releases light. Different fluorophores (FLR) can provide the color.

Modern glow sticks use less toxic chemicals to produce energy, but the fluorescent dyes are pretty much the same.

Fluorescent Dyes Used in Glow Sticks

Glow sticks are activated by breaking a glass tube, allowing phenyl oxalate and fluorescent dye to mix with a hydrogen peroxide solution.
DarkShadow / Getty Images

If fluorescent dyes weren't put in glow sticks, you probably wouldn't see any light at all. This is because the energy produced from the chemiluminescence reaction is usually invisible ultraviolet light.

These are some fluorescent dyes that may be added to light sticks to release colored light:

  • Blue: 9,10-diphenylanthracene
  • Blue-Green: 1-chloro-9,10-diphenylanthracene (1-chloro(DPA)) and 2-chloro-9,10-diphenylanthracene (2-chloro(DPA))
  • Teal: 9-(2-phenylethenyl) anthracene
  • Green: 9,10-bis(phenylethynyl)anthracene
  • Green: 2-Chloro-9,10-bis(phenylethynyl)anthracene
  • Yellow-Green: 1-Chloro-9,10-bis(phenylethynyl)anthracene
  • Yellow: 1-chloro-9,10-bis(phenylethynyl)anthracene
  • Yellow: 1,8-dichloro-9,10-bis(phenylethynyl)anthracene 
  • Orange-Yellow: Rubrene
  • Orange: 5,12-bis(phenylethynyl)-naphthacene or Rhodamine 6G
  • Red: 2,4-di-tert-butylphenyl 1,4,5,8-tetracarboxynaphthalene diamide or Rhodamine B
  • Infrared: 16,17-dihexyloxyviolanthrone, 16,17-butyloxyviolanthrone, 1-N,N-dibutylaminoanthracene, or 6-methylacridinium iodide 

Although red fluorophores are available, red-emitting light sticks tend not to use them in the oxalate reaction. The red fluorophores are not very stable when stored with the other chemicals in the light sticks and can shorten the shelf life of the glow stick. Instead, a fluorescent red pigment is molded into the plastic tube that encases the light stick chemicals. The red-emitting pigment absorbs the light from the high yield (bright) yellow reaction and re-emits it as red. This results in a red light stick that is approximately twice as bright as it would have been had the light stick used the red fluorophor in the solution.

Make a Spent Glow Stick Shine

Glow sticks

C. Fountainstand / Flickr / CC BY 2.0

You can extend the lifetime of a glow stick by storing it in the freezer. Reducing the temperature slows the chemical reaction, but the flip side is the slower reaction doesn't produce as bright a glow. To make a glow stick glow more brightly, immerse it in hot water. This speeds the reaction, so the stick is brighter but the glow doesn't last as long.

Because the fluorophor reacts to ultraviolet light, you can usually get an old glow stick to glow simply by illuminating it with a black light. Keep in mind, the stick will only glow as long as the light shines. The chemical reaction that produced the glow cannot be recharged, but the ultraviolet light provides the energy needed to make the fluorophor emit visible light.

Sources

  • Chandross, Edwin A. (1963). "A new chemiluminescent system". Tetrahedron Letters. 4 (12): 761–765. doi:10.1016/S0040-4039(01)90712-9
  • Karukstis, Kerry K.; Van Hecke, Gerald R. (April 10, 2003). Chemistry Connections: The Chemical Basis of Everyday Phenomena. ISBN 9780124001510.
  • Kuntzleman, Thomas Scott; Rohrer, Kristen; Schultz, Emeric (2012-06-12). "The Chemistry of Lightsticks: Demonstrations To Illustrate Chemical Processes". Journal of Chemical Education. 89 (7): 910–916. doi:10.1021/ed200328d
  • Kuntzleman, Thomas S.; Comfort, Anna E.; Baldwin, Bruce W. (2009). "Glowmatography". Journal of Chemical Education. 86 (1): 64. doi:10.1021/ed086p64
  • Rauhut, Michael M. (1969). "Chemiluminescence from concerted peroxide decomposition reactions". Accounts of Chemical Research. 3 (3): 80–87. doi:10.1021/ar50015a003