Tailoring long lasting luminescence of red-emitting CaWO4:Eu3+, Sm3+ nanoparticles with enhanced crystallinity for improved bio-imaging

A fast and mild synthesis procedure for nanoparticles that consist of CaWO4:Eu3+, Sm3+ and exhibit persistent luminescence is described here. Using co-precipitation in diethylene glycol and subsequently heating afforded a barely crystalline product which shows no afterglow. After a short 30 min annealing step, the increased crystallinity leads to visible persistent luminescence. A correlation between crystallinity of the product and the persistence of the luminescence is clearly demonstrated. Because of preferred red emission due to the doped Eu3+ ions, these nanoparticles can be employed in bio-imaging as demonstrated here.