Mediating sequential turn-on and turn-off fluorescence signals for discriminative detection of Ag and Hg via readily available CdSe quantum dots.

Realizing the accurate recognition and quantification of heavy metal ions is pivotal but challenging in the environmental, biological, and physiological science fields. In this work, orange fluorescence emitting quantum dots (OQDs) have been facilely synthesized by one-step method. The participation of silver ion (Ag) can evoke the unique aggregation-induced emission (AIE) of OQDs, resulting in prominent fluorescence enhancement, which is scarcely reported previously. Moreover, the Ag-triggered turn-on fluorescence can be continuously shut down by mercury ion (Hg). This intriguing sequential fluorescence variation exhibits great sensing potency for discrimination and quantification of Ag and Hg. Meanwhile, our OQDs also exhibit good selectivity, sensitivity, and rapid response toward Ag and Hg detection. Due to their high performance, OQDs have been applied to the determination of Ag and Hg levels in daily necessities and water samples with satisfactory results. Moreover, a portable smartphone-assisted sensing platform based on chromatic change has been constructed, facilitating the real-time and naked-eye visualization in the resource-confined scene. We anticipate that the discovery of these OQDs would be advantageous for exploring novel QDs materials for fluorescence detection.