Microchimica Acta

, 185:466 | Cite as

Solvothermal synthesis of phosphorus and nitrogen doped carbon quantum dots as a fluorescent probe for iron(III)

  • Khalid M. OmerEmail author
  • Diary I. Tofiq
  • Aso Q. Hassan
Original Paper


Carbon quantum dots (CQDs) doped with phosphorus and nitrogen were prepared via a hydrothermal method starting from citric acid, urea and phosphoric acid in dimethylformamide solution. The size, morphology, surface composition, energy levels, and optical properties of the CQDs were characterized. They show both green down-conversion and up-conversion fluorescence. Ferric ions (Fe3+) are found to quench the fluorescence. Cyclic voltammetry was used to identify the HOMO and LUMO levels of the doped CQDs. The quenching mechanism, as confirmed by energy level calculations and absorption spectra, can be attributed to the selective coordination of Fe3+ by the surface functional groups on the CQDs. This facilitates the photo-induced electron transfer from the CQDs to the d orbitals of Fe3+. The CQDs are shown to be viable fluorescent probes for determination of Fe3+ with high selectivity and sensitivity. The assay has a linear response in the 0.1 μM to 0.9 μM Fe3+ concentration range and a 50 nM as limit of detection (at a S/N ratio of 3).

Graphical abstract

Fluorescence probe for determination of ferric ions based on carbon quantum dot quenching via chelation facilitate photo-electron transfer.


Carbon quantum dots (CQDs) Ferric ions Phosphorus doping Nitrogen doping Fluorescent probe Photo-electron transfer Cyclic voltammetry 



The authors would like to thank the ministry of higher education and scientific research in Kurdistan for supporting this work.

Compliance with ethical standards

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

Supplementary material

604_2018_3002_MOESM1_ESM.docx (121 mb)
ESM 1 (DOCX 120 mb)


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Copyright information

© Springer-Verlag GmbH Austria, part of Springer Nature 2018

Authors and Affiliations

  1. 1.Department of Chemistry, College of ScienceUniversity of SulaimaniSulaimaniIraq
  2. 2.Komar University of Science and TechnologySulaymaniyahIraq

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