Dual-Mode Luminescent Colloidal Spheres from Monodisperse Rare-Earth Fluoride Nanocrystals

Monodisperse rare-earth fluoride nanocrystals are synthesized and used as building blocks to fabricate dual-mode luminescent colloidal spheres, which are composed of two distinct units, one offering down-converting luminescence under UV excitation and the other providing up-converting luminescent emission when excited with a 980 nm laser, and have potential applications in multiplexed and highly sensitive bioassays.