Ligand-to-Metal Charge Transfer Quenching of Carbon Dots for Highly Selective Hg<sup>2+</sup> Detection in Microfluidic Devices
Rongzhen Ma, Lin Chang, Long D. Nghiem, Yuan Liu, Qilin Wang, Qianbin Zhao, Qingju Hao, Yimeng Gao, Hong Liu, Lei Zheng
Abstract
Carbon dots have emerged as highly efficient and versatile fluorescent probes for detecting and quantifying Hg 2+ . This study reports a method to prepare nitrogen-doped carbon dots (N-CDs) via ligand-to-metal charge transfer fluorescent quenching for Hg 2+ detection. Besides the excitation-independent emission feature, the synthesized N-CDs demonstrate a high selectivity of Hg 2+ over 23 potentially interfering environmental ions. The structures of 2-hydroxy- N, N -dimethylbenzamide and amide functional groups are identified as the determinants of the relatively high quantum yield (53.33%). N-CDs also exhibit a linear relationship with Hg 2+ concentration in the range of 0.007–120 μM, with a limit of detection of 7.1 nM. The produced N-CDs can be employed in a customized microfluidic real-time monitoring platform, demonstrating the robustness in receiving efficient fluorescence signals with a satisfactory limit of detection. The acceptable accuracy and recovery of Hg 2+ detection in tap water and river water highlight the potential practical applications of the synthesized N-CDs. Results in this study can facilitate the development of a portable device for early warning of water pollution.