Selective spectrofluorimetric determination of sulfide ion using manganese doped ZnS quantum dots as luminescent probe.

This work reports a spectrofluorimetric method for selective and sensitive determination of sulfide ion in aqueous solution. The ultra-small zinc sulfide quantum dots (QDs) doped with manganese (ZnS:Mn) were synthesized by using a simple and fast procedure based on the co-precipitation of nanoparticles in aqueous solution in the presence of 2-mercaptoethanol, as capping agent. The nanoparticles have exhibited two strong fluorescent emissions at about 424 and 594 nm. Luminescent surface-capped ZnS:Mn QDs, with particle size below 5 nm, have been applied for determination of sulfide anions in water samples. Under the optimum conditions, the fluorescence intensity of ZnS:Mn QDs is linearly proportional to the sulfide ion concentration in the range 1.2×10(-6) to 2.6×10(-5) mol L(-1) with a detection limit as 3.3×10(-7) mol L(-1). The relative standard deviation for five replicate measurements (for 8.0×10(-6) mol L(-1) of S(2-)) was obtained to be 2.6%. It was founded that the interference of the other anions was negligible on the quantitive determination of sulfide ion.