Oil of wintergreen makes for lovely glowsticks, but the secret ingredient is the solvent used to create chemiluminescence.
From the recipe used:
A new oxalate ester made from methyl salicylate (oil of wintergreen) was found to be an excellent replacement for the typical halogenated oxalate ester (bis(2,4,6-trichlorophenyl) oxalate) used in peroxyoxalate chemiluminescence demonstrations. This new compound is easily prepared and has good solubility in organic solvents, such as ethyl acetate, which is an environmentally friendly solvent to use in the demonstration.
This recipe glows better and longer, and the ingredients are better for the environment than some other recipies out there.