Ninwong Benjawan, Sangkaew Prapaporn, Hapa Photcharapan, Ratnarathorn Nalin, Menger Ruth F, Henry Charles S, Dungchai Wijitar
Organic Synthesis, Electrochemistry & Natural Product Research Unit, Department of Chemistry, Faculty of Science, King Mongkut's University of Technology Thonburi Prachautid Road, Thungkru Bangkok 10140 Thailand
Nanomaterials Chemistry Research Unit, Department of Chemistry, Faculty of Science and Technology, Nakhon Si Thammarat Rajabhat University Nakhon Si Thammarat 80280 Thailand.
RSC Adv. 2020 Mar 9;10(17):9884-9893. doi: 10.1039/d0ra00791a. eCollection 2020 Mar 6.
This article reports the first fluorescent distance-based paper device coupled with an evaporating preconcentration system for determining trace mercury ions (Hg) in water. The fluorescent nitrogen-doped carbon dots (NCDs) were synthesized by a one-step microwave method using citric acid and ethylenediamine. The fluorescence turn-off of the NCDs in the presence of Hg was visualized with a common black light, and the distance of the quenched fluorescence correlated to Hg concentration. The optimal conditions for pH, NCD concentration, sample volume, and reaction time were investigated. Heating preconcentration was used to improve the detection limits of the fluorescent distance-based paper device by a factor of 100. Under the optimal conditions, the naked eye limit of detection (LOD) was 5 μg L Hg. This LOD is sufficient for monitoring drinking water where the maximum allowable mercury level is 6 μg L as established by the World Health Organization (WHO). The fluorescent distance-based paper device was successfully applied for Hg quantification in water samples without interference from other cations. The proposed method provides several advantages over atomic absorption spectroscopy including ease of use, inexpensive material and fabrication, and portability. In addition, the devices are simple to fabricate and have a long shelf-life (>5 months).
本文报道了首个基于荧光距离的纸质装置，该装置与蒸发预浓缩系统相结合，用于测定水中的痕量汞离子（Hg）。采用柠檬酸和乙二胺通过一步微波法合成了荧光氮掺杂碳点（NCDs）。在汞存在的情况下，NCDs的荧光猝灭通过普通黑光即可观察到，猝灭荧光的距离与汞浓度相关。研究了pH值、NCD浓度、样品体积和反应时间的最佳条件。采用加热预浓缩将基于荧光距离的纸质装置的检测限提高了100倍。在最佳条件下，肉眼检测限（LOD）为5 μg/L Hg。该检测限足以监测饮用水，世界卫生组织（WHO）规定饮用水中汞的最大允许含量为6 μg/L。基于荧光距离的纸质装置成功应用于水样中汞的定量分析，不受其他阳离子的干扰。与原子吸收光谱法相比，该方法具有使用方便、材料和制作成本低以及便携等优点。此外，该装置制作简单，保质期长（>5个月）。
