Integration of Cd:ZnS QDs into ZIF-8 for enhanced selectivity toward Cu2+ detection

Abstract

Metal–organic frameworks (MOFs) have been extensively studied for enhancing the performances of fluorescent probes based on the host–guest chemistry, while the selectivity enhancement of fluorescent probes through integration into MOFs is still relatively rare. In this work, Cd:ZnS QDs were integrated into ZIF-8 that could specifically interact with Cu²⁺ for fluorescence sensing. The fluorescence of Cd:ZnS QDs was quenched by Cu²⁺ based on cation exchange, while this phenomenon was also observed in the presence of Mn²⁺, Co²⁺ and Ni²⁺. By contrast, only Cu²⁺ induced the fluorescence quenching of Cd:ZnS QDs@ZIF-8 as a result of its specific interaction with ZIF-8. In addition, Cd:ZnS QDs@ZIF-8 displayed a fast response of 1 min and a low detection limit of 16 nM toward Cu²⁺, and moreover, it was successfully applied to detecting Cu²⁺ in water samples with spiked recoveries ranging from 90.1 to 109.8%. These results indicate that integration into ZIF-8 is an efficient strategy to enhance the selectivity of fluorescent probes toward Cu²⁺.