Nitrogen-doped carbon dots (N-CDs), derived from the biomass (anthocyanin), are the novel additive to the nanocarbon materials, which is expected to bring a wide spectrum of novel applications. Moreover, metallic oxides are emerging for their unique potential for electrocatalysis. Herein, we report the synthesis of N-CDs for the selective detection of Fe3+ with a limit of detection of 2.57 μM in the range of 5–60 μM using ethylenediamine and H2O2 by a hydrothermal method. The obtained N-CDs displayed a spherical morphology with a particle size range of 2–7 nm and emitted blue luminescence at 394 nm under excitation at 319 nm. Meanwhile, we have demonstrated the fabrication of cost-efficient electrocatalysts for oxygen evolution reaction (OER) in an alkaline medium, employing N-CDs. Owing to the successful incorporation of N-CDs into NiO nanospheres, the resulting N-CDs/NiO with large surface areas, fast charge transfer, and increased conductivity vastly improved the catalytic activity. Remarkably, the optimal of N-CDs/NiO composite requires the overpotential of only 380 mV at a current density of 10 mA cm− 2 and a relatively low Tafel slope of 57.96 mV dec− 1 compared with pure NiO. These results open up a facile route for the application of N-CDs and offer prospects for CD-metal hybrids as high OER catalysts in electrochemical energy devices.

    Abstract
    1 Introduction
    2 Experimental section
        2.1 Materials
        2.2 Synthesis of N-CDs
        2.3 Preparation of N-CDsNiO composite
        2.4 Fe ion detection
        2.5 Electrochemical measurements
        2.6 Material characterization
    3 Results and discussion
        3.1 Optical and microscopic studies of N-CDs
        3.2 Structural and morphological analyses of N-CDsNiO composite
        3.3 Fluorescence response of N-CDs to Fe3+
        3.4 Electrochemical activity of N-CDsNiO toward OER
    4 Conclusion
    Acknowledgements 
    References

• Xiaoli Kou(State Key Laboratory of Chemical Engineering, East China University of Science and Technology)
• Xin Xin(Department of Environmental Science, Department of Chemistry, Yanbian University)
• Yan Zhang(First Senior High School of Xiong County)
• Long‑Yue Meng(Department of Environmental Science, Department of Chemistry, Yanbian University)