Electrochemiluminescence　(ECL)　emission　of　gold　nanoparticles　(Au　NPs)　loaded　graphitic　carbon　nitride　nanosheets　(Au-CNN　nanohybrids)　can　be　modulated　by　the　Au　content.　On　the　basis,　a　signal-on　ECL　sensor　for　detecting　cyanide,　a　widespread　toxic　chemical,　has　been　developed　in　this　work.　The　sensor　utilizes　cyanide-mediated　etching　of　Au　NPs　to　recover　the　ECL　emission　of　Au-CNN　nanohybrids　initially　inhibited　by　Fӧrster　resonance　energy　transfer　(FRET)　from　CNNs　to　Au　NPs.　The　ECL　sensor　has　a　sensitive　response　to　cyanide　in　the　range　of　50　nM　to　1　mM　with　a　detection　limit　of　50　nM,　and　shows　high　specificity　due　to　the　high　affinity　of　Au-cyanide　complex.　The　proposed　FRET　modulated　ECL　sensor　may　prove　valuable　in　future　environmental　monitoring.　©　2017　Elsevier　Ltd