I believe this is the same stuff that makes up Stuart Semple's Lit glow powder and other such glow-in-the-dark pigments. It's a mix of europium and dysprosium.

I believe this is the same stuff that makes up Stuart Semple's Lit glow powder and other such glow-in-the-dark pigments. It's a mix of europium and dysprosium. IIRC what makes it last so long is the addition of trap states for the electrons, where instead of quickly re-emitting absorbed photons they can give up a little bit of energy to remain in the trap state, and are later bumped back out of that state by random thermal fluctuations. I tried it out on some cardboard and it's almost as impressive as the marketing makes it sounds. I can hold a cheap LED headlamp next to it and wave it over the surface, and it leaves a bright green streak behind that glows visibly for many hours afterward. It doesn't stay bright for very long (I suspect it's an exponential decay), but for such a short exposure I wouldn't expect it to. The blue version is less impressive because you need sunlight or a proper UV light source to charge it up, but it does work.