A fluorescence sensor for basic amino acids based on WS2 nanosheets- silver oxide nanoparticles (WS2 NSs-Ag2O NPs) composite materials has been developed. The composite was prepared via the in situ formation of silver oxide nanoparticles (Ag2O NPs) by the combined action of fluorescent WS2 nanosheets (WS2 NSs) in the presence of NaOH. The fluorescence of WS2 NSs was quenched upon the formation of Ag2O NPs due to resonance energy transfer. The obvious spectral overlap of WS2NSs emission with that of surface plasmon resonance (SPR) absorption of Ag2O NPs explains the non-radiative energy transfer. The quenched fluorescence was selectively recovered in the presence of three basic amino acids; His, Lys and Arg, at a pH below the isoelectric point of each amino acid. The fluorescence recovery was attributed to the aggregation of Ag2O NPs and thereby the lack of spectral overlap between WS2NSs and Ag2O NPs. The formation of Ag2O NPs, the comprehensive mechanism of quenching and the fluorescence recovery. The real sample analysis was demonstrated using biological fluids.