Question: how does carbon react to light?

Clara Zehe answered on 15 Mar 2023:

Carbon itself does not react with light. The interaction of the carbon particles with light that I am interested in is actually a physical process (i.e. no chemical reaction takes place).
In this interaction, the carbon particle can absorb light that comes from the sun or a light bulb. This increases the energy of the particle (we say, it gets raised to an excited state). To get rid of all that extra energy, the particle can then send out light – this is called luminescence. Luminescence also happens when you put a colourful t-shirt under a black light lamp. A lot of carbon dots emit light in the visible spectrum, i.e. colours that we can see with our eyes. They can be blue, green, yellow or red. The photo of my profile shows green-yellow ones! Scientists are still undecided why exactly this happens because the carbon element itself or the molecules we use to make carbon dots don’t do that on their own. So I am working on finding that out!