Ultrasensitive determination of lead and chromium contamination in well and dam water based on fluorescence quenching of CdS quantum dots

We report lead (Pb2?) and chromium (Cr3?) determination in several water samples obtained from Nahand dam, Karkaj and Azarshahr well, tab and mineral waters to study their contamination in these systems. Determination method is based on the characteristic aggregation and fluorescence quenching of synthesized CdS quantum dots (QDs) at 555 nm by considered cations. Water-soluble and biocompatible CdS QDs modified with thioglycolic acid have been synthesized in one step and characterized by fluorescence and absorption spectroscopy. The fluorescence intensity of CdS QDs is linearly proportional to Pb2? and Cr3? concentration from 0.8 to 100 and 3 to 400 ng mL-1 with a detection limit of 0.3 and 1.2 ng mL-1 , respectively. Other potentially interfering ions such as iron, sodium, potassium, calcium, and magnesium ions did not affect the luminescence. The method showed lower detection blank and higher sensitivity.