A fluorescent nanoparticle includes a core comprising an alkenylbenzene; an intermediate layer, an outer shell layer, and a fluorescent portion. The fluorescent portion includes a structure represented by the following formula: wherein L is a direct bond or a linker group, and F is any fluorescent moiety. The fluorescent portion is located in at least one of the following locations: the core, the intermediate layer, or the shell layer of the nanoparticle. Methods for making the fluorescent nanoparticle are also described.