ZnO nanoparticles were successfully synthesized within the free volume of an ethylene vinyl acetate (EVA) polymer sheet. Using a process termed “nanoinfusion,” nanoparticles are created in situ. Vapor phase nanoparticle precursors first filled the polymer free volume. Nucleated components of the precursor molecule within the free volume enabled nanoparticle formation and immobilization within the polymer. Trapped nanoparticles were accessible to gas diffusion and can be modified as was demonstrated by the successful conversion of nanoinfused ZnO to ZnS nanoparticles. Successful nanoparticle formation was confirmed through fluorescence spectroscopy and the amount of material nanoinfused was obtained through thermal gravimetric analysis. The nanoinfused ZnO and ZnS exhibited unexpectedly high fluorescent quantum yields, significantly higher than that observed for comparable materials. © 2013 Society of Plastics Engineers