How Do Lightsticks Work?
What is a Lightstick and How Does it Operate?
Lightsticks or glowsticks are used by trick-or-treaters, divers, campers, and for
decoration and fun! A lightstick is a plastic tube with a glass vial inside of it. In
order to activate a lightstick, you bend the plastic stick, which breaks the glass
vial. This allows the chemicals that were inside the glass to mix with the
chemicals in the plastic tube. Once these substances contact each other, a
reaction starts taking place. The reaction releases light, causing the stick to
glow!
A Chemical Reaction Releases Energy
One form of energy is light. Some chemical reactions release energy; the
chemical reaction in a lightstick releases energy in the form of light. The light
produced by this chemical reaction is called chemiluminescence.
Although the light-producing reaction is not caused by heat and may not
produce heat, the rate at which it occurs is affected by temperature. If you
place a lightstick in a cold environment (like a freezer), then the chemical
reaction will slow down. Less light will be released while the lightstick is cold,
but the stick will last much longer. On the other hand, if you immerse a
lightstick in hot water, the chemical reaction will speed up. The stick will glow
much more brightly, but will wear out faster too.
What's Involved?
There are three components of a lightstick. There need to be two chemicals
that interact to release energy and also a fluorescent dye to accept this energy
and convert it into light. Although there is more than one recipe for a
lightstick, a common commercial lightstick uses a solution of hydrogen
peroxide that is kept separate from a solution of a phenyl oxalate ester
together with a fluorescent dye. The color of the fluorescent dye is what
determines the resulting color of the lightstick when the chemical solutions are
mixed. The basic premise of the reaction is that the reaction between the two
chemicals releases enough energy to excite the electrons in the fluorescent
dye. This causes the electrons to jump to a higher energy level and then fall
back down and release light.
Specifically, the chemical reaction works like this: The hydrogen peroxide
oxidizes the phenyl oxalate ester, to form phenol and an unstable peroxyacid
ester. The unstable peroxyacid ester decomposes, resulting in phenol and a
cyclic peroxy compound. The cyclic peroxy compound decomposes to carbon
dioxide. This decomposition reaction releases the energy that excites the dye.