Reduction of mercury(II) by electrons contained in carbon dots: An environmentally friendly cold vapor generation for mercury analysis

• Published in: Chinese chemical letters 2020-10, Vol.31 (10), p.2678-2682
• Main Authors: Chen, Tao, Lin, Yao, Li, Haochen, Yang, Rui, Hou, Xiandeng, Zheng, Baozhan, Zheng, Chengbin
• Format: Article
• Language: English
• Subjects: Carbon dots; Cold vapor generation; Mercury analysis; Reduction
• ISSN: 1001-8417; 1878-5964
• DOI: 10.1016/j.cclet.2020.06.005

Reduction of mercury(II) to elemental mercury was easily achieved using carbon dots (r-CDs) synthesized from sucrose. This reduction was accomplished with the large numbers of electrons contained in r-CDs rather than the oxidation of its functional groups. [Display omitted] In this work, the reduction of mercury ions (Hg2+) to elemental mercury (Hg0) was easily achieved using highly reductive carbon dots (r-CDs), which synthesized from sucrose by a simple and cost-effective method. After a careful mechanistic study, the reduction was probably accomplished with the large numbers of electrons contained in r-CDs rather than the oxidation of its functional groups. Additionally, a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay showed that the r-CDs were nontoxic to wildlife and human beings. Consequently, the r-CDs were used as an alternative to toxic reductants (SnCl2 or NaBH4) for the sensitive and in situ determination of mercury by cold vapor generation (CVG) coupled to a miniature point discharge optical emission spectrometer (μPD-OES). Limit of detection of 0.05 μg/L was obtained for Hg2+, with relative standard deviation (RSD) less than 5.4% at a concentration of 5 μg/L. The accuracy of r-CDs induced CVG-μPD-OES was validated by the determination of mercury in a certified reference material (DOLT-5, dogfish liver) and five natural water samples collected from different rivers and lakes in Chengdu City. Since r-CDs are nontoxic and prepared from abundant and inexpensive sucrose, the r-CDs induced CVG-μPD-OES retains the great potential for the inexpensive and environmentally friendly field analysis of mercury in natural water. The accuracy of the proposed method was validated by the analysis of a certified reference material and several water samples with satisfactory results.