Abstract The present study was aimed to use of N doped graphene quantum dots (N-GQDs) and N,K co-doped graphene quantum dots (N,K-GQDs) as a fluorescence quenching sensor to determine both mercury and copper in water sample, simultaneously using simple fluorescence protocol. Each of N-GQDs or N,K-GQDs was optimized separately with 1–5% (w/v) HNO3 or KNO3, respectively, and their quantum yields were determined and compared. It was found that N-GQDs, obtained from 3% (w/v) HNO3 doped resulted higher fluorescence intensity at the maximum excitation and emission wavelengths of 370 and 460 nm, respectively, with higher quantum yield (QY = 83.42%) compared with that of undoped GQDs (QY = 16.35%). While N,K-GQDs obtained from 5%(w/v) KNO3 gave somewhat different fluorescence spectrum, but still had the same maximum excitation and emission wavelengths with rather highest QY (94.07%). However, it is interesting that detection sensitivity expressed as slope of their calibration curve (y = 5.43x − 19.48; r2 = 0.9971) of the N-GQDs is rather higher than that (y = 1.29x + 17.66; r2 = 0.9977) of the N,K-GQDs for Hg2+ fluorescence quenching sensor, and the fluorescence intensity of N-GQDs had better selectively quenching effect only by both Hg2+ and Cu2+. Thus, their quenching effects were selected to develop the fluorescence turn-off sensor for trace level of both metal ions in real water samples. For method validation, the N-GQDs exhibited high sensitivity to detect both Hg2+ and Cu2+ with wide linear ranges of 20–100 μM and 100–500 μM, respectively. Limit of detection (LOD) and limit of quantitation (LOQ) were 0.42 μM & 1.41 μM for Hg2+ and 13.19 μM & 43.97 μM for Cu2+, respectively, with their precision expressed as an intra-day and an inter-day analysis of 6.98% & 11.35% for Hg2+ and 11.78% & 9.43% for Cu2+, respectively. Also the study of matrix analysis of the water samples (drinking water and tap water), was carried out using N-GQDs and N,K-GQDs resulted good percentage recoveries in comparison with those using undoped GQDs under the same optimum conditions.

中文翻译：

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使用 n 掺杂和 n,k 共掺杂石墨烯量子点的荧光猝灭传感器同时测定水样中的 hg(ii) 和 cu(ii)

摘要 本研究旨在利用 N 掺杂石墨烯量子点 (N-GQDs) 和 N,K 共掺杂石墨烯量子点 (N,K-GQDs) 作为荧光猝灭传感器来测定水样中的汞和铜。 ，同时使用简单的荧光协议。每个 N-GQD 或 N,K-GQD 分别用 1-5% (w/v) HNO3 或 KNO3 分别优化，并确定和比较它们的量子产率。发现从 3% (w/v) HNO3 掺杂获得的 N-GQDs 在最大激发和发射波长分别为 370 和 460 nm 时产生更高的荧光强度，与更高的量子产率 (QY = 83.42%) 相比未掺杂的 GQD (QY = 16.35%)。虽然从 5%(w/v) KNO3 获得的 N,K-GQDs 的荧光光谱略有不同，但仍然具有相同的最大激发和发射波长，QY 相当高（94.07%）。然而，有趣的是，用 N-GQD 的校准曲线斜率 (y = 5.43x − 19.48; r2 = 0.9971) 表示的检测灵敏度远高于 (y = 1.29x + 17.66; r2 = 0.9977) Hg2+荧光猝灭传感器的N,K-GQDs，N-GQDs的荧光强度只有Hg2+和Cu2+具有更好的选择性猝灭效果。因此，选择它们的猝灭效应来开发荧光关闭传感器，用于实际水样中两种金属离子的痕量水平。对于方法验证，N-GQD 表现出高灵敏度，可以检测 Hg2+ 和 Cu2+，线性范围分别为 20-100 μM 和 100-500 μM。检测限 (LOD) 和定量限 (LOQ) 为 0.42 μM & 1。Hg2+ 为 41 μM，Cu2+ 为 13.19 μM 和 43.97 μM，其精度表示为日内和日间分析，Hg2+ 为 6.98% 和 11.35%，Cu2+ 为 11.78% 和 9.43%。此外，使用 N-GQD 和 N,K-GQD 对水样（饮用水和自来水）进行基质分析的研究与在相同最佳条件下使用未掺杂 GQD 的那些相比获得了良好的回收率。