A Mn-doped ZnS quantum dots-based ratiometric fluorescence probe for lead ion detection and "off-on" strategy for methyl parathion detection.

In the present study, a novel ratiometric fluorescence probe based on dual-emitting Mn-doped ZnS quantum dots (Mn:ZnS QDs) was established for detection of Pb2+ and methyl parathion (MP). The dual-emitting Mn:ZnS QDs was aqueous synthesised in one pot and played as a ratiometric fluorescence probe for the detection of Pb2+ with high sensitivity. The fluorescence intensity ratio (F450nm/F585nm) of the probe against the concentration of Pb2+ showed a good linear relationship from 10 nM to 60 nM with a detection limit of 0.5 nM. Furthermore, the Mn:ZnS QDs/Pb2+ system was established as a turn-on fluorescence sensing system to quantitative measure the MP concentration. The fluorescence intensity at 450 nm exhibited a good linear relationship in the MP concentration range from 0.19 to 0.95 μM with a detection limit of about 0.02 μM. It also had a satisfying performance in fruit and environmental water samples. Therefore, the prepared Mn:ZnS QDs-based sensor has been established as a ratiometric fluorescence probe and turn-on method for quantitative detection of lead ion and MP, respectively.