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Demonstrative Projects for Glow-in-the-Dark Tomatoes

All things that glow in the dark contain some kind of phosphor. The scientific property of luminescent phosphors can be creatively demonstrated by making common objects, such as tomatoes, actually glow. Glowing tomatoes is a relatively simple experiment which takes under an hour to do, and it is a fun, memorable way to show how the chemical reaction of phosphors is what makes glow-in-the-dark toys possible.

Phosphors
- A phosphor is a substance that radiates a glow after being energized by some other energy source. The absorbed energy is released in the form of light. This is why you are sometimes instructed to hold a glow-in-the-dark toy up to a light source for a short time before it will glow in the dark. Chemists have created many substances which behave like phosphors, including Zinc Sulfide and Strontium Aluminate, to be used in manufacturing. Phosphors are used in objects such as TV screens, computer screens, and fluorescent lights as well as children's toys.
Obtaining Materials for the Experiment
- You will need a tomato, a liquid phosphor, household hydrogen peroxide and a syringe to inject the chemicals into the tomato. The tomato used need not be of any particular size. For the phosphor, you can scrape the red material off of match heads and submerge them in bleach. Use just enough bleach so that the match heads are submerged. Once the match heads have fully dissolved and the liquid has sat for about 20 minutes, there should be two layers in the container -- one liquid and one solid. The liquid layer may be used as a phosphor.
Making a Tomato Glow
- Use a syringe to inject the uncut tomato with phosphor liquid. Move the needle over one inch and inject again, and continue all the way around the tomato. Then, fill the syringe with hydrogen peroxide and inject the tomato repeatedly in order to activate the phosphor. The tomato will soon begin to glow. The use of a phosphor in this experiment is most similar to a common glow stick where a small container inside the glow stick is cracked open in order to mix two chemicals inside. The chemical reaction of mixing these two substances energizes the phosphor and produces a glow.
Warnings and Tips
- Wait to inject the tomato with hydrogen peroxide until you are ready to display the effect because the luminescence wears off after a couple hours just like glow-sticks. Prepare the experiment and display the glowing tomatoes in a contained area where there is no danger of dripping chemicals causing any harm. Also, use gloves and have a water faucet available to wash off any chemicals that may inadvertently splash on your body. After the experiment, the tomato should definitely not be eaten because the chemicals injected into the tomato are very poisonous.

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