In　this　work,　we　study　the　enhancement　of　Raman　signals　and　photocatalytic　activity　of　Ag/ZnO　heterojunctions　with　an　Ag　content　of　1　at.%,　which　were　synthesized　by　photochemical　deposition　of　Ag　nanoparticles　onto　pre-synthesized　ZnO　nanorods.　A　strong　interaction　between　Ag　and　ZnO　nanocrystals　were　evidenced　by　XPS　and　UV-vis　spectroscopy.　The　binding　energy　of　Ag　nanoparticles　shifts　toward　lower　energy　compared　to　that　of　pure　Ag　nanoparticles,　revealing　that　electrons　transfer　from　Ag　to　the　ZnO　nanocrystals.　The　red　shift　of　the　plasmon　absorption　peak　of　Ag　nanoparticles　in　Ag/ZnO　heterojunctions　further　confirms　the　strong　interaction　between　the　two　components.　This　strong　interaction,　arising　from　the　coupling　between　Ag　and　ZnO　nanocrystals,　is　responsible　for　the　enhancement　of　Raman　signals　and　photocatalytic　activity　of　the　Ag/ZnO　heterojunctions.　©　2011　The　Royal　Society　of　Chemistry.