There is provided herein cross-linked, phosphorescent micro- and nano-particles and applications of those particles. The invention uses halogen-containing polymers and co-polymers (HCPs) as an encapsulation matrix for organic and organometallic phosphorescent compounds to form micro- or nano-particles. The phosphorescence of these encapsulated phosphorescent particles is substantially unaffected by phosphorescence quenchers such as oxygen and water molecules at ambient conditions. The invention provides methods of making cross-linked phosphorescent particles. HCPs may be directly cross-linked through linking moieties that are a part of the polymer, or cross-linked through other separate bridging or cross-linking materials Cross-linked particles are more stable than the non-cross-linked counterparts and more resistant to temperature, surfactants, and organic solvents.