Is it possible to manufacture fluorescent ink?

Answer 1

Yes, fluorescent inks can be manufactured. And they are. To keep it simple, something that is fluorescent will fluoresce under high energy light, usually ultraviolet light. This high energy light will be absorbed by the fluorphore, and it will re-emit light of a lower energy, usually in the visible spectrum where we can see it. (The rest of the light energy of the incoming light will retained as heat - atomic and/or molecular vibration.) Fluorescent markers find application in the security or property control area where they are used to mark things like chairs or tables or stuff like that. The marks are invisible under normal circumstances, but will fluoresce and become visible under black light. Certainly there are still posters that are printed with fluorescent ink and look cool under black light.