A must for birthday or end of year parties, neon bracelets and sticks glow in the dark. Yellow, pink, blue or green, whatever the color of the light, these sticks transform the house to create exceptional atmospheres. And then here’s a great idea to transform yourself into a Jedi!
How can these bracelets emit light without electricity?
To get light from a lamp, you need a bulb and an electrical outlet. But for neon bracelets, it works differently, you just have to twist them!
Weird isn’t it?
Chemilinescence
It’s a chemical reaction that releases energy in the form of light.
How do luminescent sticks work?
Inside the stick, there is a glass tube containing a colored liquid which itself bathes in a liquid. When you twist the stick, the inner tube breaks, and the two liquids mix. By mixing, the molecules react with each other and light is emitted.
Usually, a chemical reaction releases heat. But here the result of the reaction produces light. This is called chemiluminescence.
To be more concrete, inside the glass tube, there are molecules that we call dyes. They are the ones that will emit light of the desired color after the reaction.
The outer liquid is made up of potassium hydroxide, a “basic” compound that solubilizes the dye in water, and hydrogen peroxide. Oxygenated water will cause a reaction that chemists call: an oxidation reaction.
In practice, it will “oxidize” the dye by transforming it into another molecule. The latter is very excited. To return to an energy state, the excited electrons descend to a lower energy level and emit light. Depending on the energy level, the color will be different.
To obtain a blue color, we use luminol.
For pink: diphenol oxalate
Why does the neon bracelet go out after a few hours?
Once all the dye molecules have reacted with the hydrogen peroxide, the light disappears.
To make the bracelets shine longer, the reaction must be slowed down. The trick will, therefore, be to lower the temperature. We can even pause the reaction by putting the sticks in the fridge. And the reaction then resumes when we take it out of the fridge.
Is it possible to recharge the neon bracelets?
No, it is impossible to recharge the neon bracelets, because it is impossible to return to the starting molecules. The reaction is said to be irreversible.
Did you know ?
These luminescent sticks are also very useful for other applications like illuminating the depths in scuba diving or signaling its position with emergency lights.
Luminol reacts quickly with small amounts of iron. So the police inspectors use it as a spray at crime scenes to determine the presence of blood (iron being responsible for the red color of blood).