We have successfully synthesized core-shell nanoparticles with a silica fluorescent core and a methacrylate shell for application in photoactive high performance coatings and paints. Silica core particles with diameters between 270 and 440 nm and low polydispersity were labeled with a perylenediimide derivate with two terminal alkoxysilyl groups. Pure silica nanoparticles with equivalent diameters were also synthesized and surface modified with a second perylenediimide derivative. The photophysical properties of both sets of nanoparticles were studied for polarity environment dependence and dye aggregation. The fluorescent silica nanoparticles were surface modified with 3-(trimethoxysilyl)propyl methacrylate and used as seeds in the emulsion polymerization of a butyl or methyl methacrylate shell. Fluorescence correlation spectroscopy (FCS) was used to characterize the core-shell nanoparticles, using the fluorescent silica particles to calibrate the system. Films cast from water dispersions of clean core-shell nanoparticles are flexible, transparent, and exhibit fluorescence under appropriate excitation.