Microchimica Acta

, 186:341 | Cite as

Dually emitting carbon dots as fluorescent probes for ratiometric fluorescent sensing of pH values, mercury(II), chloride and Cr(VI) via different mechanisms

  • Bo Li
  • Hong Ma
  • Bo Zhang
  • Jing Qian
  • Ting Cao
  • Haitao Feng
  • Wu Li
  • Yaping DongEmail author
  • Wenwu QinEmail author
Original Paper


The authors describe the preparation of carbon dots (CDs) that display both blue (~ 410 nm) and yellow (~ 565 nm) emission peaks. The CDs was synthesized by solvothermal treatment of o-phenylenediamine in aqueous ethyl alcohol at pH ~7.0. The CDs are shown to be useful fluorescent probes for pH values in that the ratio of fluorescences at 565 and 410 nm strongly depends on the pH value in the range from 4.5–6.5 and 10.0–13.0, respectively. The blue fluorescence is quenched by 91% by 100 µM solutions of Hg(II) through an electron transfer process, and is restored by 97% an addition of chloride (0.5 mM). The yellow fluorescence, in contrast, is hardly affected. The ratio of fluorescences at 414 and 565 nm drops linearly in the 30 to 60 μM of Hg(II) concentration range, and the limit of detection is 60 nM. Fluorescence is linearly restored in the 70 to 180 μM chloride concentration range, and the LOD is 2.8 nM. Both the blue and the yellow emission are reduced by Cr(VI) (chromate) due to an inner filter effect at pH 3.0. The ratio of fluorescences (410/565 nm) drops linearly in the 20 to 250 μM Cr(VI) concentration range, and the LOD is 260 nM. The method was utilized to analysis of chloride in salt lake brine and of Cr(VI) in spiked tap water.

Graphical abstract

Schematic presentation of carbon dots with pH-dependent dual emission (at ~ 410 nm and ~ 565 nm). They are shown to be viable fluorescent probes for ratiometric sensing of pH values, mercury(II), chloride and Cr(VI) via different mechanisms.


Carbon dots Ratiometric fluorescent probes pH value Hg2 +  Cl Cr(VI) 



This work is supported by the Natural Science Foundation of China (no. 21771092), Natural Science Foundation in Qinghai Province (No: 2019-ZJ-940Q, 2019-ZJ-946Q), Major Science and Technology Project in Qinghai Province (No: 2016-GX-A10) and Basic Research Rroject in Qinghai Province (No: 2017-ZJ-786). CAS “Light of West China” Program and Youth Innovation Promotion Association, CAS (No: Y810071022 and Y810061021).

Compliance with ethical standards

The author(s) declare that they have no competing interests.

Supplementary material

604_2019_3437_MOESM1_ESM.doc (9.2 mb)
ESM 1 (DOC 9386 kb)


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Copyright information

© Springer-Verlag GmbH Austria, part of Springer Nature 2019

Authors and Affiliations

  • Bo Li
    • 1
    • 2
  • Hong Ma
    • 3
  • Bo Zhang
    • 1
    • 2
  • Jing Qian
    • 3
  • Ting Cao
    • 3
  • Haitao Feng
    • 1
    • 2
  • Wu Li
    • 1
    • 4
  • Yaping Dong
    • 1
    • 2
    Email author
  • Wenwu Qin
    • 3
    Email author
  1. 1.Key Laboratory of Comprehensive and Highly Efficient Utilization of Salt Lake Resources, Chinese Academy of SciencesQinghai Institute of Salt LakesXiningPeople’s Republic of China
  2. 2.Qinghai Engineering and Technology Research Center of Comprehensive Utilization of SaltLake ResourcesXiningPeople’s Republic of China
  3. 3.Key Laboratory of Nonferrous Metal Chemistry and Resources Utilization of Gansu ProvinceLanzhou UniversityLanzhouPeople’s Republic of China
  4. 4.Key Laboratory of Salt Lake Resources Chemistry of Qinghai ProvinceXiningPeople’s Republic of China

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