Provided is a phosphor-functionalized nanoparticle that includes an inorganic nanoparticle core; surface polymer brushes that include a plurality of long-chain polymers bonded to the surface of the inorganic nanoparticle core, said long-chain polymers each having molecular weight greater than 500, and a plurality of short-chain polymers bonded to the surface of the inorganic nanoparticle core, said short-chain polymers each having molecular weight less than 0.5 times the average molecular weight of the long-chain polymers; and one or more organic phosphors bonded to at least one of the inorganic nanoparticle core and one or more of the plurality of short-chain polymers. Graft density of the short-chain polymers on the surface of the inorganic nanoparticle core (σSC) is greater than graft density of the long-chain polymers on the surface of the inorganic nanoparticle core (σLC). Also provided are polymer matrices, LED's, optical systems, lighting devices, and fixtures that include the inventive nanoparticle.