What is fluorescence?

And why should you know?

What is she doing in the lab, you ask? Isn’t that dangerous? Who let her in there? Don’t worry! I’m nowhere near a laboratory and these pictures are actually from my sister. For some reason, she became a talented scientist and is currently writing her bachelor thesis in nanoscience with a specialisation in organic chemistry. And she is doing pretty cool stuff and I only understand half of it. But I do understand the part about fluorescence and it’s not only pretty but also very useful.

At the very core, fluorescence is the emission of light after the absorption of energy. Most commonly known is absorption of light in our visible light spectrum or from the UV spectrum and it’s very pretty to look upon. That’s all to it. But what does that even mean?

Fluorescence of different substances under UV light.

The material absorbs energy from the electromagnetic radiation that falls upon it. And as soon as the electromagnetic radiation vanishes, the energy has to be re-emitted and we can now see the fluorescent light. Color and brightness are determined by properties of the compounds we’re investigating and that’s the beauty to all that comes with fluorescence.

But if you’re thinking about the glow-in-the-dark stars we probably all had as children, that is a phosphorescent material and something slightly different. They don’t emit the light right away but take some time and therefore glow longer.

So why is a nanoscientist working on fluorescent materials? Because they’re handy and very useful for all sorts of applications. Fluorescence is part of analytical chemistry, used for spectroscopy and used in biochemistry and medicine. It’s important to know all properties of the fluorescent materials and maybe even synthesize new compounds with fluorescent properties.

Obviously, there is much more to the matter than just the simple explanation of light emission after energy absorption. It has got to do for example with the multiplicity of the energy ground state of molecules, the spin angular momentum and how the electrons behave when the energy gets absorbed. I believe the most important thing to remeber though is not all the technical details but that we can use light and especially the energy to make compounds visible in order to further analyze either the compounds themselves or whatever they are in.

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