ZnS quantum dots as fluorescence sensor for quantitative detection of tetracycline

X–ZnS quantum dots (QDs) are synthesized in aqueous solution by a simple aqueous chemical route where X represents 3-mercaptopropionic acid (MPA) or 3-mercapto-1-propanesulfonic acid (MPS) which are two well-known low cost and stable ligands. The synthesized X–ZnS QDs yielded aqueous suspensions of nanoparticles with excellent monodispersity, water solubility and fluorescence stability with a relatively high fluorescence quantum yield of 11% and 10% for MPA-ZnS QDs and MPS-ZnS QDs respectively. Under optimal conditions, the prepared X–ZnS QDs are used to detect tetracycline (TC) based on their fluorescence quenching induced by the target analyte via electrostatic interaction. The Stern–Volmer-type equation has been fitted to the quenching curve of each QDs, from which MPA-ZnS QDs has shown a larger linear range and a lower limit of detection than MPS-ZnS QDs. The fluorescence response of MPA-ZnS QDs is linearly with respect to TC concentration over a wide range from 200 nM to 6000 nM with a detection limit of 30 pM. The combination of non-toxicity, simplicity and low cost together with high analytical performance of the proposed MPA-ZnS QDs make it promising for the determination of trace TC in food products of animal origin.