A fluorescence turn-on CDs-AgNPs composites for highly sensitive and selective detection of Hg²

In this paper, a simple and effective fluorescence turn-on approach for highly sensitive and selective monitoring Hg²⁺ ions was designed by using carbon dots (CDs) and silver nanoparticles (AgNPs). It reveals that the fluorescence of CDs solution can be quenched in the presence of AgNPs through inner filter effect (IFE) and the quenched CDs-AgNPs system is turned on after addition of Hg²⁺ ions, which is due to higher affinity of Hg²⁺ and AgNPs than that of CDs and AgNPs, thus resulting the disappearance of AgNPs from the CDs-AgNPs composites and leading to the fluorescence turn-on of CDs. The developed fluorescence turn-on approach exhibited high selectivity and sensitivity for detection of Hg²⁺. Under the optimum experimental conditions, good linearity was achieved over the range of 100-160 μM and the limit of detection (LOD) was estimated to be 2.22×10^-8 M for Hg²⁺. The recoveries of Hg²⁺ spiked in real samples ranged from 98.4% to 101.6%. Results of this study suggest that the fluorescence turn-on approach can be used to the detection of Hg²⁺ in real water samples.