AbstractA rapid method has been developed for the determination of Hg(II) and sulfide by using graphitic carbon nitride quantum dots (g-CNQDs) as a fluorescent probe. The interaction between Hg(II) and g-CNQDs leads to the quenching of the blue g-CNQD fluorescence (with excitation/emission peaks at 390/450 nm). However, the fluorescence can be recovered after addition of sulfide such that the “turn-off” state is switched back to the “turn-on” state. The g-CNQDs were fully characterized by transmission electron microscopy, X-ray diffractometry, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, UV-vis absorption and fluorescence spectroscopy. Under the optimal experimental conditions, this probe is highly selective and sensitive to Hg(II). The linear response to Hg(II) extends from 0.20 to 21 μM with a detection limit of 3.3 nM. In addition, sulfide can be detected via the recovery of fluorescence. The linear response range for sulfide species is from 8.0 to 45 μM with a detection limit of 22 nM. The mechanism of the “turn-off-on” scheme is discussed. The methods have been applied to the analysis of spiked tap water, lake water and wastewater samples. Graphical abstractSchematic of an off-on fluorescent probe for mercury(II). The fluorescence of graphitic carbon nitride quantum dots (g-CNQDs) is quenched by Hg2+ but is recovered after reacting with S2− as it can combine with Hg2+ on the surface of g-CNQDs.

中文翻译：

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石墨氮化碳量子点作为“关-开”荧光开关，用于测定汞 (II) 和硫化物

摘要 建立了一种使用石墨氮化碳量子点 (g-CNQDs) 作为荧光探针快速测定 Hg(II) 和硫化物的方法。Hg(II) 和 g-CNQD 之间的相互作用导致蓝色 g-CNQD 荧光猝灭（激发/发射峰位于 390/450 nm）。然而，在加入硫化物后可以恢复荧光，使得“关闭”状态切换回“开启”状态。通过透射电子显微镜、X 射线衍射、X 射线光电子能谱、傅里叶变换红外光谱、紫外-可见吸收和荧光光谱对 g-CNQDs 进行了全面表征。在最佳实验条件下，该探针对 Hg(II) 具有高度选择性和敏感性。对 Hg(II) 的线性响应范围从 0.20 到 21 μM，检测限为 3。3纳米。此外，硫化物可以通过荧光的恢复来检测。硫化物种类的线性响应范围为 8.0 至 45 μM，检测限为 22 nM。讨论了“关闭-开启”方案的机制。这些方法已应用于分析加标自来水、湖水和废水样品。汞 (II) 的关断式荧光探针的图形摘要示意图。石墨氮化碳量子点 (g-CNQDs) 的荧光被 Hg2+ 淬灭，但在与 S2- 反应后恢复，因为它可以与 g-CNQDs 表面的 Hg2+ 结合。这些方法已应用于分析加标自来水、湖水和废水样品。汞 (II) 的关断式荧光探针的图形摘要示意图。石墨氮化碳量子点 (g-CNQDs) 的荧光被 Hg2+ 淬灭，但在与 S2- 反应后恢复，因为它可以与 g-CNQDs 表面的 Hg2+ 结合。这些方法已应用于分析加标自来水、湖水和废水样品。汞 (II) 的关断式荧光探针的图形摘要示意图。石墨氮化碳量子点 (g-CNQDs) 的荧光被 Hg2+ 淬灭，但在与 S2- 反应后恢复，因为它可以与 g-CNQDs 表面的 Hg2+ 结合。