What properties of a compound gives ultra-violet signature?

this is especially for thin layer chromatography. what makes some of the spots visible under uv light?

What properties of a compound gives ultra-violet signature?
A compound that is uv visible (using TLC) is one that absorbs ultraviolet light and prevents the dye in the silica gel coating on the TLC plate from "glowing".





Such molecules usually have one or more of the following properties: unsaturated (particularly conjugated molecules), have an aromatic ring, a sulfur atom, higher halogen atom, etc. Good luck.