Analytical and Bioanalytical Chemistry

, Volume 411, Issue 12, pp 2531–2543 | Cite as

Ratiometric fluorescent sensor for visual determination of copper ions and alkaline phosphatase based on carbon quantum dots and gold nanoclusters

  • Haijian Liu
  • Lu Jia
  • Yixuan Wang
  • Mengyao Wang
  • Zideng GaoEmail author
  • Xueqin RenEmail author
Research Paper


In this work, a novel ratiometric fluorescent sensor, based on carbon dots (CDs) and gold nanoclusters (AuNCs), is developed for highly sensitive and selective visual colorimetric detection of Cu2+ and alkaline phosphatase (ALP). The ratiometric fluorescent sensor was synthesized by covalently linking 11-mercaptoundecanoic acid (11-MUA)–stabilized AuNCs to the surface of amino-functionalized CD/SiO2 nanoparticles. The red fluorescence of the AuNCs can be quenched by Cu2+ owing to coordination between Cu2+ and 11-MUA; however, the blue emission of the CDs was insensitive to Cu2+ owing to the protective silica shell. The quenching of the AuNCs’ fluorescence returned when PPi was added because of the higher affinity between Cu2+ and PPi than that between Cu2+ and 11-MUA. In the presence of ALP, PPi was catalytically hydrolyzed into phosphate (Pi), which showed a much weaker affinity for Cu2+. Thus, Cu2+ ions were released, and the fluorescence of the AuNCs was quenched once more. Based on this principle, Cu2+ and ALP could be simultaneously detected. The developed ratiometric fluorescent sensor could detect Cu2+ over a range from 0.025 to 4 μM with a detection limit of 0.013 μM and ALP over a range from 0.12 to 15 U/L with a detection limit of 0.05 U/L. The present method was successfully applied for the detection of Cu2+ and ALP in real water samples and in human serum samples, respectively. This ratiometric fluorescent approach may provide a highly sensitive and accurate platform for visual Cu2+ and ALP sensing in environmental monitoring and medical diagnosis.


Ratiometric fluorescent sensor Visual determination Copper ions Alkaline phosphatase Carbon quantum dots Gold nanoclusters 


Funding information

This work was supported by the Chinese National Scientific Foundation (21375146 and 21775163) and The National Key Research and Development Program of China (2016YFC0501205 and 2016YFC0501208).

Compliance with ethical standards

Ethical approval

All biological experiments were performed with the approval of the Human Ethics Committee, China Agricultural University. Informed consent was obtained from all individual participants included in the study.

Conflict of interest

The authors declare that they have no competing interests.

Supplementary material

216_2019_1693_MOESM1_ESM.pdf (958 kb)
ESM 1 (PDF 958 kb)


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Copyright information

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

Authors and Affiliations

  1. 1.College of Chemistry and EnvironmentWeifang University of Science and TechnologyWeifangChina
  2. 2.Department of Environmental Science and Engineering, College of Resources and Environmental SciencesChina Agricultural UniversityBeijingChina

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