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Nitrogen-Doped Carbon Dots: A Facile and General Preparation Method, Photoluminescence Investigation, and Imaging Applications

Authors

  • Yang Xu,

    1. State Key Laboratory of Medicinal Chemical Biology and Key Laboratory of Functional Polymer Materials (MOE), College of Chemistry, Nankai University, Tianjin, 300071 (P.R. China), Fax: (+86) 22-2350-2458
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    • These authors contributed equally to this work.

  • Ming Wu,

    1. State Key Laboratory of Medicinal Chemical Biology and the Key Laboratory of Bioactive Materials (MOE), College of Life Science, Nankai University, Tianjin, 300071 (P.R. China)
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    • These authors contributed equally to this work.

  • Yang Liu,

    1. State Key Laboratory of Medicinal Chemical Biology and the Key Laboratory of Bioactive Materials (MOE), College of Life Science, Nankai University, Tianjin, 300071 (P.R. China)
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  • Prof. Dr. Xi-Zeng Feng,

    1. State Key Laboratory of Medicinal Chemical Biology and the Key Laboratory of Bioactive Materials (MOE), College of Life Science, Nankai University, Tianjin, 300071 (P.R. China)
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  • Prof. Dr. Xue-Bo Yin,

    Corresponding author
    1. State Key Laboratory of Medicinal Chemical Biology and Key Laboratory of Functional Polymer Materials (MOE), College of Chemistry, Nankai University, Tianjin, 300071 (P.R. China), Fax: (+86) 22-2350-2458
    • State Key Laboratory of Medicinal Chemical Biology and Key Laboratory of Functional Polymer Materials (MOE), College of Chemistry, Nankai University, Tianjin, 300071 (P.R. China), Fax: (+86) 22-2350-2458
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  • Prof. Xi-Wen He,

    1. State Key Laboratory of Medicinal Chemical Biology and Key Laboratory of Functional Polymer Materials (MOE), College of Chemistry, Nankai University, Tianjin, 300071 (P.R. China), Fax: (+86) 22-2350-2458
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  • Prof. Yu-Kui Zhang

    1. State Key Laboratory of Medicinal Chemical Biology and Key Laboratory of Functional Polymer Materials (MOE), College of Chemistry, Nankai University, Tianjin, 300071 (P.R. China), Fax: (+86) 22-2350-2458
    2. Dalian Institute of Chemical Physics, National Chromatographic R. & A. Center Chinese Academy of Sciences, 161 Zhongshan Road, Dalian 116011 (P.R. China)
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Abstract

Carbon dots (Cdots) are an important probe for imaging and sensing applications because of their fluorescence property, good biocompatibility, and low toxicity. However, complex procedures and strong acid treatment are often required and Cdots suffer from low photoluminescence (PL) emission. Herein, a facile and general strategy using carbonization of precursors and then extraction with solvents is proposed for the preparation of nitrogen-doped Cdots (N-Cdots) with 3-(3,4-dihydroxyphenyl)-L-alanine (L-DOPA), L-histidine, and L-arginine as precursor models. After they are heated, the precursors become carbonized. Nitrogen-doped Cdots are subsequently extracted into N,N′-dimethylformamide (DMF) from the carbogenic solid. A core–shell structure of Cdots with a carbon core and the oxygen-containing shell was observed. Nitrogen has different forms in N-Cdots and oxidized N-Cdots. The doped nitrogen and low oxidation level in N-Cdots improve their emission significantly. The N-Cdots show an emission with a nitrogen-content-dependent intensity and Cdot-size-dependent emission-peak wavelength. Imaging of HeLa cells, a human cervical cancer cell line, and HepG2 cells, a human hepatocellular liver carcinoma line, was observed with high resolution using N-Cdots as a probe and validates their use in imaging applications and their multicolor property in the living cell system.

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