Fluorescence resonance energy transfer (FRET) process as a practical and competitive sensing strategy was utilized between carbon quantum dots (C-dots) and silver nanoparticles (Ag NPs) for the determination of mercuric ions. The novel synthesized C-dots with the quantum yield of 84% acted as the donor and Ag NPs operated as the acceptor in the FRET process leading to the fluorescence quenching of the C-dots. In the presence of Hg(II) ions, the FRET-quenched fluorescence emission of the C-dots–Ag NPs system was recovered owing to oxidation of Ag NPs by Hg(II) ions, so that the turn-on fluorescence intensity was directly proportional to the Hg(II) ion concentration. Accordingly, combination of the FRET system with the redox reaction was firstly utilized to construct an innovative turn-off/on fluorescent sensor for the quantification of Hg(II) ion. The calibration plot was linear in the concentration range 0.5–500.0 nmol L⁻¹ with a determination coefficient (R²) of 0.9965. The limit of detection and limit of quantification were 0.10 and 0.35 nmol L⁻¹, respectively, according to the IUPAC definition. The method was applied for the determination of Hg(II) ion in lake water, wastewater and tea samples, and the proper relative recoveries (98.0–104.0%) were obtained for the spiked samples. The method has high potential to diagnose trace values of mercuric ions in real samples with high sensitivity and repeatability.

在碳量子点（C-dots）和银纳米颗粒（Ag NPs）之间采用了荧光共振能量转移（FRET）工艺作为一种实用且具有竞争性的传感策略来测定汞离子。在FRET过程中，量子产率为84％的新型合成C点充当了施主，Ag NP充当了受体，导致了C点的荧光猝灭。在存在Hg（II）离子的情况下，由于Hg（II）离子氧化了Ag NPs，因此恢复了C-dots-Ag NPs系统的FRET猝灭荧光发射，因此开启荧光强度直接与Hg（II）离子浓度成正比。因此，首先利用FRET系统与氧化还原反应的结合来构建创新的关闭/开启荧光传感器，用于定量Hg（II）离子。^-1，测定系数（R ²）为0.9965。根据IUPAC定义，检测极限和定量极限分别为0.10和0.35nmol L ^-1。该方法用于测定湖水，废水和茶叶样品中的Hg（II）离子，并且加标样品的适当相对回收率（98.0–104.0％）。该方法具有很高的灵敏度和重复性，可用于诊断实际样品中的痕量汞离子。