Macademics: Luminescence

Hey everyone. I have to say this year is flying by! I can't believe it's October already! Since Halloween is on the horizon, you'll probably start seeing (if you haven't already) a lot of decorations that include glow in the dark pumpkins. So for my #Macademics installment this month, I'm going to tell you why they glow in the dark and how to make your own!

First things first, the chemistry behind glowing in the dark. You may be able to guess that anything that has to do with "glowing" means some form of light is involved. Luminescence is the spontaneous emission of light by a substance, without using heat. There are a lot of ways to get substances to emit light. If you use a chemical reaction, it's called chemiluminescence, using an electric current is called electroluminescence, and photoluminescence (the one I'm going to focus on) means a substance emits light after absorbing a photon.

Photons are essentially the fundamental particles of light. If compound A absorbs a photon, it gains energy, gets excited, and eventually releases that extra energy in the form of light. Think about when you give a child some sugar. They eat it , gain an excessive amount of energy, and then crash. The "glow-in-the-dark" effect comes from a process called phosphorescence. This means that the time it takes for the compound emit the extra energy as light is really slow, causing the long-term glow that can last from minutes to hours (substance depending). Back to my "giving a child some sugar" analogy. Say you're at an amusement park and you give them sugar. They're going to still spend hours at the park playing all the games and riding the rides before crashing in the car on the ride home. Toys, paints, stickers, etc. all have a special ingredient(s) that can engage in phosphorescence, which is why they're really cool to use for decorations.

Now that you have a working knowledge of how things glow in the dark, here's a Halloween demo!

Materials

- Pumpkin (real, carved, or artificial)

- Glow in the dark paint

- Paintbrush (optional)

- Masking tape to form a jack-o-lantern face (optional)

Make the Pumpkin Glow

- Paint your pumpkin.

- Shine a bright light on it, then turn out the lights.

If the pumpkin does not glow as brightly as you would like, apply one or more coats of glow in the dark paint.

If you just want a glowing pumpkin, you simply coat the pumpkin with glow in the dark paint, and you're finished.

Creating a Jack-o-Lantern Face

If you are using a carved jack-o-lantern, you've already got a face.

But, if you want a face on an intact pumpkin you have a few different options for creating it:

- Trace a face on the pumpkin and paint around the face.

- Tape a face on the pumpkin, paint the entire pumpkin and remove the tape when the paint is dry. For this project, the jack-o-lantern face is the part that does not glow.

I hope you all try out this demo! If you do, tag me and #MacScientist in it!

See you next week!

-The Chemist