A　novel　fluorescent　biosensor　for　detecting　uranyl　ion　(UO22+)　in　aqueous　environment　has　been　developed　based　on　the　specific　recognition　of　DNAzyme　and　the　fluorescence　quenching　ability　of　molybdenum　disulfide　(MoS2)　nanosheets.　The　DNAzyme　contains　a　DNA　enzyme　strand　and　a　6-carboxylfluorescein　(FAM)-labeled　DNA　substrate　strand.　We　demonstrated　that　MoS2　nanosheets　have　low　affinity　to　the　substrate-enzyme　complex　DNAzyme.　Whereas,　in　the　presence　of　UO22+,　UO22+　can　specifically　cleave　DNAzyme　to　release　FAM-labeled　single-strand　DNA　and　the　released　FAM-labeled　single-strand　DNA　can　be　firmly　adsorbed　on　the　surface　of　MoS2　nanosheets,　which　resulted　in　an　obvious　decrease　of　fluorescence　intensity.　This　provided　a　sensing　platform　for　the　rapid,　simple　and　sensitive　fluorescent　detection　of　UO22+.　By　using　the　sensing　platform,　a　sensitive　and　selective　fluorescent　method　for　the　rapid　detection　of　UO22+　has　been　developed.　In　comparison　with　previous　biosensor,　the　proposed　method　has　obvious　analytical　advantage　such　as　relatively　high　sensitivity　and　good　stability,　short　analytical　time　and　low　cost.　It　can　be　used　to　detect　as　low　as　2.14　nM　of　UO22+　in　aqueous　environment　with　a　recovery　of　96-102%　and　a　RSD　＜　5%　(n　=　6).　The　success　of　this　study　provides　a　promising　alternative　for　the　rapid　and　on-site　detection　of　UO22+　in　environmental　monitoring.　(C)　2015　Elsevier　B.V.　All　rights　reserved.