Highly Sensitive Fluorescent Determination of Chromium(VI) by the Encapsulation of Cadmium Telluride Quantum Dots (CdTe QDs) into Zeolitic Imidazolate Framework-8 (ZIF-8)

Chromium (VI) [Cr(VI)] is considered to be a serious environmental pollutant because of its highly carcinogenic and mutagenic properties. In this study, we fabricated fluorescent probes for Cr(VI) detection by encapsulating cadmium telluride quantum dots (CdTe QDs) into zeolitic imidazolate framework-8 (ZIF-8). The obtained composites, designated as CdTe QDs@ZIF-8, were able to sense Cr(VI) through the combined action of fluorescence dynamic and static quenching. Under the optimum conditions, the obtained CdTe QDs@ZIF-8 composites showed high selectivity and sensitivity toward Cr(VI). The fluorescence intensity of the CdTe QDs@ZIF-8 composites decreased as the concentration of Cr(VI) increased across from the range of 2.5 to 40 μM with a detection limit of 0.06 μM. The CdTe QDs@ZIF-8 composites were successfully applied to determine Cr(VI) in tap water and seawater samples; the average recoveries of Cr(VI) at different spiking concentration levels ranged from 94.0% to 104.1% with relative standard deviations below 4.8%. This work provides a novel fluorescent detection method for Cr(VI) and discrimination between Cr(VI) and Cr(III), which can be used for rapid recognition and determination of Cr(VI) in complex matrices.