Nelson D James, Vasimalai N, John S Abraham, Sethuraman M G
Department of Chemistry, The Gandhigram Rural Institute-Deemed to be University, Gandhigram, Dindigul, 624302, Tamilnadu, India.
Department of Chemistry, B.S. Abdur Rahman Crescent Institute of Science and Technology, Vandalur, Chennai, 600048, Tamilnadu, India.
J Fluoresc. 2025 Feb;35(2):1139-1150. doi: 10.1007/s10895-024-03598-9. Epub 2024 Feb 1.
This research introduces a novel fluorescence sensor 'on-off-on' employing nitrogen-doped carbon dots (N-CDs) with an 'on-off-on' mechanism for the selective and sensitive detection of Hg(II) and L-cysteine (L-Cys). N-CDs was synthesized using citric acid as the carbon precursor and urea as the nitrogen source in dimethylformamide (DMF) solvent, resulting in red emissive characteristics under UV light. Comprehensive spectroscopic analyses, including UV-Vis, fluorescence, FT-IR, XRD, XPS, Raman, and Zeta potential techniques, validated the structural and optical characteristics of the synthesized N-CDs. The maximum excitation and emission of N-CDs were observed at 548 and 622 nm, respectively. The quantum yield of N-CDs was calculated to be 16.1%. The fluorescence of N-CDs effectively quenches upon the addition of Hg(II) due to the strong coordination between Hg(II) and the surface functionalities of N-CDs. Conversely, upon the subsequent addition of L-Cys, the fluorescence of N-CDs was restored. This restoration can be attributed to the stronger affinity of the -SH group in L-Cys towards Hg(II) relative to the surface functionalities of N-CDs. This dual-mode response enabled the detection of Hg(II) and L-Cys with impressive detection limits of 15.1 nM and 8.0 nM, respectively. This sensor methodology effectively detects Hg(II) in lake water samples and L-Cys levels in human urine, with a recovery range between 99 and 101%. Furthermore, the N-CDs demonstrated excellent stability, high sensitivity, and selectivity, making them a promising fluorescence on-off-on probe for both environmental monitoring of Hg(II) and clinical diagnostics of L-Cys.
本研究介绍了一种新型的“开-关-开”荧光传感器，该传感器采用氮掺杂碳点（N-CDs），具有“开-关-开”机制，用于选择性和灵敏地检测Hg(II)和L-半胱氨酸（L-Cys）。以柠檬酸为碳源前驱体、尿素为氮源，在二甲基甲酰胺（DMF）溶剂中合成了N-CDs，其在紫外光下具有红色发光特性。通过紫外可见光谱、荧光光谱、傅里叶变换红外光谱、X射线衍射、X射线光电子能谱、拉曼光谱和zeta电位技术等综合光谱分析，验证了合成的N-CDs的结构和光学特性。N-CDs的最大激发波长和发射波长分别为548 nm和622 nm。计算得出N-CDs的量子产率为16.1%。由于Hg(II)与N-CDs表面官能团之间的强配位作用，加入Hg(II)后N-CDs的荧光有效猝灭。相反，随后加入L-Cys后，N-CDs的荧光恢复。这种恢复可归因于L-Cys中的-SH基团对Hg(II)的亲和力强于N-CDs的表面官能团。这种双模式响应能够分别以15.1 nM和8.0 nM的令人印象深刻的检测限检测Hg(II)和L-Cys。这种传感器方法能够有效地检测湖水样品中的Hg(II)和人尿中的L-Cys水平，回收率在99%至101%之间。此外,N-CDs具有优异的稳定性、高灵敏度和选择性，使其成为一种有前途的用于Hg(II)环境监测和L-Cys临床诊断的荧光“开-关-开”探针。
