[en] 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.

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