Ag@SiO2　nanoparticles　with　different　shell　thicknesses　were　synthesized　via　modified　Stober　method.　Rhodamine　B　isothiocyanate　was　covalently　bound　onto　the　surface　of　Ag@SiO2　nanoparticles　to　form　fluorescent　core-shell　Ag@SiO2　nanocomposites.　Effects　of　shell　thickness　on　the　fluorescence　enhancement　were　examined　using　the　corresponding　nanobubbles　prepared　by　cyanide　etching　as　a　control.　The　result　showed　that　the　fluorescence　enhanced　as　the　shell　thickness　increased　till　the　distance　between　fluorophore　and　metal　core　reached　about　75　nm　with　the　optimal　enhancement　factor　of　similar　to　5-folds.　Further　increasing　of　fluorophore-metal　distance　caused　a　decrease　in　the　enhancement　factor.　(C)　2010　Elsevier　B.V.　All　rights　reserved.