Ratiometric fluorescence sensor based on dithiothreitol modified carbon dots-gold nanoclusters for the sensitive detection of mercury ions in water samples

Ratiometric fluorescence sensors can provide more accurate analysis of target objects because of their self-calibration function. Traditional methods often use steps of chemical coupling with two different fluorescent materials as the dual emission source, which make the construction process complicated and hard to control. Here, we report a convenient and effective way to construct a ratiometric fluorescence sensor based on dual-emission carbon dots-gold nanoclusters (C-AuNCs) functionalized with dithiothreitol (DTT) for the sensitive detection of mercury ions (Hg2+) in water samples. As a type of novel nanoparticle, C-AuNCs are synthesized via microwaving a mixture of gold seeds solution and carbon precursor. In the presence of Hg2+, the free thiol group of DTT would attract them around the surface of C-AuNCs, and owing to the strong 5d(10)-5d(10) metallophilic interactions between Hg2+ and Au+, the fluorescence emission at 598 nm is quenched while the emission at 466 nm remains at a constant intensity. Thus, an obvious color change from orange-red to blue under ultraviolet irradiation can be observed by the naked eye. Moreover, the as-prepared fluorescence sensor has high sensitivity with a detection limit of 8.7 nM, and successfully applies to detect Hg2+ in real water samples with satisfactory recoveries at three spiking levels ranging from 95.9 - 103.5%. The good results imply that the developed DTT/C-AuNCs sensor is conducive to trace Hg2+ determination and possesses the great application potential for water-quality monitoring. (C) 2018 Elsevier B.V. All rights reserved.