Using durian shell as a carbon source and triethanolamine as a nitrogen dopant, nitrogen-doped carbon dots (N-CDs) were prepared via the hydrothermal method. First, by exploring different reaction times, reaction temperatures, and carbon source/dopant ratios to synthesize nitrogen-doped carbon dots, it is concluded that the best process conditions are 200 ℃, reaction time being 15h, and the dopant addition amount being 2mL. Structure and characteristics of the synthesized CDs were analyzed using X-ray photoelectron spectroscopy, Fourier-transform infrared, fluorescence (FL), ultraviolet–visible absorption, and Raman spectra. The N-CDs showed blue FL with a quantum efficiency of 4.28%. The FL characteristics of the N-CDs were utilized for ion detection, which demonstrated that MnO− 4 and Cr 2 O2− 7 ions caused distinct FL quenching through static quenching, while other ions had no significant quenching effect. The detection limits for MnO− 4 and Cr 2 O2− 7 were 37.5 and 46.2 nM, respectively. The N-CDs were subsequently employed to detect these ions in actual water samples, producing satisfactory results. Therefore, the preparation of N-CDs using durian shell as raw material and its application in practical detection work have good application feedback, which not only provides a new way for the reuse of fruit and vegetable wastes but also provides a new detection means for environmental monitoring pollutants.

Synthesis of durian shell-based carbon dots and its application in the detection of and 
    Abstract
    1 Introduction
    2 Experimental section
        2.1 Reagents and materials
        2.2 Synthesis of N-CDs
        2.3 Characterization of N-CDs
        2.4 Quantum yield measurements
        2.5 Selective and sensitive detection of  and  
    3 Results and discussion
        3.1 Preparation of N-CDs
        3.2 Characterization of N-CDs
        3.3 Optical characteristics of N-CDs
        3.4 Fluorescence sensing of  and  based on the N-CDs
        3.5 Assay for real water samples
        3.6 Detection mechanism of  and 
    4 Conclusions
    Acknowledgements 
    References

• Yuanxin Liu(School of Chemical Engineering, University of Science and Technology Liaoning, Anshan 114051, China)
• Jian Zhang(School of Chemical Engineering, University of Science and Technology Liaoning, Anshan 114051, China)
• Yaming Zhu(School of Chemical Engineering, University of Science and Technology Liaoning, Anshan 114051, China) Corresponding author
• Xuefei Zhao(School of Chemical Engineering, University of Science and Technology Liaoning, Anshan 114051, China)
• Chaoshuai Hu(School of Chemical Engineering, University of Science and Technology Liaoning, Anshan 114051, China, Hebei Vocational University of Industry and Technology, Shijiazhuang 050091, China)
• Xitao Yin(School of Physics and Optoelectronic Engineering, Ludong University, Yantai 264000, China)