Ag@SiO2　nanoparticles　with　different　shell　thicknesses　were　synthesized　via　modified　Stöber　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　∼5-folds.　Further　increasing　of　fluorophore-metal　distance　caused　a　decrease　in　the　enhancement　factor.　©　2010　Elsevier　B.V.