I have used 12vdc LED strips that produce UV and they will cause flourescense (sp?), but perhaps not as bright as from a UV tube type. The problem is that UV material is very spectrum sensitive. If you are using commercial paint products, they should give you the correct frequency spectrum. You need to buy LEDs that are very close to that frequency for maximum effect. If you get an exact match, the difference is amazing.
In case you haven't tried it, a mild solution of Tide laundry detergent, sprayed onto walls and fabric, will glow like crazy under black light.