Electrochemical synthesis of FeNx doped carbon quantum dots for sensitive detection of Cu2+ ion

• Published in: Green energy & environment 2023-02, Vol.8 (1), p.141-150
• Main Authors: Sun, Siyuan, Bao, Weijie, Yang, Fan, Yan, Xingru, Sun, Yang, Zhang, Ge, Yang, Wang, Li, Yongfeng
• Format: Article
• Language: English
• Subjects: Cu2+ detection; Electrolysis; FeNx-doped CQDs; pH compatibility; Quick response
• ISSN: 2468-0257; 2468-0257
• DOI: 10.1016/j.gee.2021.04.005

A novel strategy was developed to fabricate FeNx-doped carbon quantum dots (Fe-N-CQDs) to detect Cu2+ ions selectively as a fluorescence probe. The Fe-N-CQDs were synthesized by an efficient electrolysis of a carbon cloth electrode, which was coated with monoatomic iron-anchored nitrogen-doped carbon (Fe-N-C). The obtained Fe-N-CQDs emitted blue fluorescence and possessed a quantum yield (QY) of 7.5%. An extremely wide linear relationship between the Cu2+ concentration and the fluorescence intensity was obtained in the range from 100 nmol L−1 to 1000 nmol L−1 (R2 = 0.997), and the detection limit was calculated as 59 nmol L−1. Moreover, the Fe-N-CQDs demonstrated wide range pH compatibility between 2 and 13 due to the coordination between pyridine nitrogen and Fe3+, which dramatically reduced the affection of the protonation and deprotonation process between H+ and Fe-N-CQDs. It is notable that the Fe-N-CQDs exhibited a rapid response in Cu2+ detection, where stable quenching can be completed in 7 s. The mechanism of excellent selective detection of Cu2+ was revealed by energy level simulation that the LUMO level of Fe-N-CQDs (−4.37 eV) was close to the redox potential of Cu2+, thus facilitating the electron transport from Fe-N-CQDs to Cu2+. The FeNx structure are reserved integrally in Fe-N-CQDs from Fe-N-C through a simple chemical oxidation method. Fe-N-CQDs-2 exhibits excellent selectivity to Cu2+, outstanding pH compatibility and fast response in metal ions detection. Energy level simulation and fluorescence lifetime detection reveal that the LUMO of Fe-N-CQDs are closer to the redox potential of Cu2+, leading to the non-radiative recombination between Fe-N-CQDs and Cu2+, which quench the fluorescence. [Display omitted] •Fe-N-CQDs was synthesized by electrolysis method from monoatomic iron-anchored nitrogen doped carbon (Fe-N-C).•Fe-N-CQDs was capable of possessing good pH compatibility and exhibiting rapidly detection response in Cu2+ detection.•The unique structure of FeNx in Fe-N-C is reserved integrally, which endows special properties to Fe-N-CQDs.