Dithizone functionalized CdSe/CdS quantum dots as turn-on fluorescent probe for ultrasensitive detection of lead ion

An ultrasensitive fluorescence turn-on probe based on dithizone (Dz) functionalized CdSe/CdS quantum dots (QDs) was prepared for the determination of lead in environmental samples. Dithizone was bound to the QDs via a surface coordinating reaction to form QDs–Dz conjugates and quench fluorescence of the QDs by fluorescence resonance energy transfer (FRET) mechanism. In the presence of Pb2+, the dithizone on the surface of the QDs was removed upon the binding of Pb2+ and the FRET pathway was shutted off. Hence the fluorescence of the QDs was recovered. [Display omitted] ► A turn-on probe for lead based on dithizone functionalized QDs was constructed. ► Unique properties of QDs were combined with specific Pb2+ affinity of dithizone. ► High sensitivity and selectivity were achieved by combination of QDs with dithizone. ► The fluorescent probe was applied to environmental samples with satisfactory results. An ultrasensitive fluorescent probe is developed for the determination of lead ion by utilizing dithizone (Dz) functionalized CdSe/CdS quantum dots (QDs). Dithizone was bound to the QDs via a surface coordinating reaction to form QDs–Dz conjugates and quench fluorescence of the QDs by fluorescence resonance energy transfer (FRET) mechanism. Upon the addition of Pb2+, a dramatic enhancement of the fluorescence intensity was observed, which resulted from the FRET pathway shutting off, and hence the fluorescence of the QDs was recovered. Two successive linear ranges of 0.01–1000nmolL−1 and 1–20μmolL−1 allow a very wide determination of Pb2+ concentration from 0.01nmolL−1 to 20μmolL−1, with a detection limit of 0.006nmolL−1. The fluorescent probe was successfully applied to the determination of lead in environmental samples with satisfactory results.