Why Glow Sticks Are Different ColorsGlow sticks get their colors from fluorescent dyes. Image By 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.
Glow Stick Chemical ReactionThe Cyalume reaction produces the colored light seen in glow sticks. Smurrayinchester
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 fluorophors (FLR) can provide the color.
Modern glow sticks use less toxic chemicals to produce the energy, but the fluorescent dyes are pretty much the same.
Fluorescent Dyes Used in Glow SticksGlow sticks are activated by breaking a glass tube, allowing phenyl oxalate and fluorescent dye to mix with a hydrogen peroxide solution. DarkShadow / Getty Images
What Color Is a Glow Stick Without Dye?
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))
- Green: 9,10-bis(phenylethynyl)anthracene
- Yellow-Green: 1-Chloro-9,10-bis(phenylethynyl)anthracene
- Yellow: 1-chloro-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 fluorophors are available, red-emitting light sticks tend not to use them in the oxalate reaction. The red fluorophors 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.
Did You Know: Make a Spent Glow Stick Shine Light
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.