What do fireflies, TVs, neon signs, and glowsticks have in common?
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Hey, it’s me, Lauren. You’ve seen glowsticks before. They bring a festive glow to Halloween trick-or-treating and New Year’s Eve celebrations, and are useful gear for explorers from scuba divers to spelunkers. When you find a bunch of people gathered to party in the dark, at least a few of them will probably be wielding glowsticks. But what the heck are these things? How do they work?”
Glow sticks are powered by a process called chemiluminescence. Don’t let the name scare you – luminescence is just a fancy word for “any emission of light not caused by heating”. We see luminescence in stuff like TVs, neon signs, and fireflies. The chemiluminescence in glowsticks is a pretty simple reaction caused by mixing chemical compounds.
Compounds are made up of different elements bonded together in specific proportions so that they can’t be mechanically separated – it takes a chemical reaction to sort out, for example, the oxygen from the hydrogen in water. When you mix a compound with other stuff, you can set off that reaction. And as the atoms rearrange themselves, they’ll either absorb or release energy.
If you look inside a glowstick, you’ll see that there’s a small glass vial in the tube. This vial typically contains a hydrogen peroxide solution called “the activator”. It’s floating in a solution containing a compound called phenyl oxalate ester and a fluorescent dye.
Still with me? Good.
When you snap a glowstick, the vial breaks, and the hydrogen peroxide reacts with the phenyl oxalate ester, creating two other compounds: phenol and a peroxyacid ester. This peroxyacid stuff is unstable, so it decomposes and produces additional phenol. It also produces a cyclic peroxy compound, which decomposes to carbon dioxide.
This decomposition releases energy to the dye. The electrons in the dye’s atoms jump to a higher level, then fall back down, releasing energy in the form of light. The other chemicals in the fluorescent dye determine the color of this light.
All this happens within moments of snapping and shaking your glowstick. Depending on which compounds are used, the chemical reaction can continue for anywhere from just a few minutes to hours.
Warmer temperatures will accelerate the reaction, making the stick glow brighter but for a shorter amount of time. When it’s cooler, the reaction will slow down, making the light dimmer.
Which means that if you want to preserve your light stick, put it in the freezer overnight -- it won't stop the process, but it will slow it down and drag out the reaction.
So it turns out that there’s some pretty nifty science behind the humble glowstick. Check it out the next time you’re SCUBA diving, partying or… you know. Whatever you do in the dark.