Crystalline　ZnO　nanoparticles　were　synthesized　via　the　templating　method　by　taking　advantage　of　the　hydrophilic　cavities　of　the　Nafion　ionomer　membranes.　The　ZnO-embedded　Nafion　film　was　characterized　by　various　methods,　including　optical　absorption,　X-ray　diffraction　and　high-resolution　transmission　electron　microscopy.　The　film　was　of　high　optical　quality,　and　exhibited　excellent　photocatalytic　activity　toward　rhodamine　B　degradation　under　UV　irradiation.　Unlike　unprotected　bulk　ZnO　nanocrystals,　the　ZnO　nanocatalysts　embedded　in　Nafion　membranes　were　found　to　be　highly　stable　against　photocorrosion,　with　hardly　any　reduction　in　the　activity　even　after　10　times　of　repeated　reaction　cycles.　The　implications　of　the　results　are　discussed.　©　2007　Elsevier　B.V.　All　rights　reserved.