Functionalized Mn2+-Doped Zinc Sulfide Quantum Dots as a Metal Ion Sensor for Industrial Wastes

l-Cysteine-capped Mn 2+ -doped ZnS quantum dots are prepared as a fluorescence probe for the detection of heavy metal contaminants, such as As 2 O 4 2-, Cd 2+ , CrO 4 2-, Ni 2+ , Zn 2+ , Ca 2+ , Fe 2+ , Cu 2+ , Pb 2+ , Co 2+ , and Mn 2+ ions. The results show that the l-cysteinecapped Mn 2+ -doped ZnS quantum dots exhibit good sensitivity and selectivity for the detection of copper ions. The optimized concentration of l-cysteine-capped Mn 2+ -doped ZnS quantum dots is determined as 2 mg/mL under pH 7.0 in phosphate buffer. The detection limit for this sensor system is 0.2 ppm with the linear range between 0.5 and 20 ppm. The effect of foreign ions such as Mn 2+ , Fe 2+ , Co 2+ , and Ni 2+ on the detection of Cu 2+ solution is also evaluated. The results show that there is no significant difference in the measurements.