A fluorescent nanoprobe based on HgS/ZnS core/shell quantum dots for in-situ rapid visual detection of Cr3+.

Heavy metal Cr3+ has been regarded as a threat to the environment and human health. So it is crucial to find a rapid method for detecting Cr3+, especially for the trace amounts. Here, HgS/ZnS core/shell quantum dots (HgS/ZnS QDs) with a quantum yield of 22.6% were synthesized as a fluorescent nanoprobe for detection of Cr3+ with a detection limit of 0.19 nM. With captopril as stabilizer, the formation of the core/shell structure of HgS/ZnS QDs was demonstrated by high-resolution high-angle annular dark-field scanning transmission electron microscopy (HR-HAADF-STEM). The substantial fluorescence (580 nm) quenching of HgS/ZnS QDs which could be seen immediately by the naked eyes was induced selectively and sensitively by Cr3+, even in the case of Cr3+ mixed with other interfering ion. The HgS/ZnS QDs exhibited a stable visual response to Cr3+ from 1 μM, which just conformed to World Health Organization (WHO) standards for drinking water. Moreover, further experiments indicated that the mechanism of fluorescence quenching lied on the aggregation of the HgS/ZnS QDs. These results provide a novel insight for in situ rapid visual detection of heavy metal ions. Graphical abstract A rapid visual method was developed for in-situ detection of Cr3+ from 1 μM (WHO standards for the drinking water) through the orange fluorescence quenching (seen by naked eyes) which resulted from the Cr3+ induced the aggregation of captopril coated HgS/ZnS core/shell QDs [ABSTRACT FROM AUTHOR]