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Deep Eutectic Solvent-Assisted Preparation of Nitrogen/Chloride-Doped Carbon Dots for Intracellular Biological Sensing and Live Cell Imaging

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journal contribution
posted on 09.02.2018, 00:00 by Ning Wang, An-Qi Zheng, Xun Liu, Jun-Jie Chen, Ting Yang, Ming-Li Chen, Jian-Hua Wang
A novel approach for the preparation of dual-functional carbon dots, i.e., nitrogen- and chloride-doped carbon dots, abbreviated as N/Cl-CDs, is developed with the assistance of a choline chloride–glycerine deep eutectic solvent (DES). The carbon source is provided by urea and the DES serves as a solvent for controlling the preparation of CDs in the absence of water. The dual-element doped carbon dots are oxygen-rich with hydroxyl and amine groups. They exhibit an average particle size of ca. 3.88 nm and give rise to strong and pH-sensitive fluorescent emission at λexem = 340/430 nm with a quantum yield of 16.15 ± 1.36%. It is particularly interesting to see that the fluorescence of N/Cl-CDs remains stable in a high-salinity matrix, providing vast potentials for treating real biological sample matrixes with high salinity. The N/Cl-CDs provide an optical probe for intracellular pH sensing and multicolor imaging in HeLa cells. In addition, the N/Cl-CDs show obvious fluorescence response to cytochrome c (cyt-c) with a detection limit of 3.6 mg L–1 (ca. 0.29 μmol L–1) within in a range of 10–500 mg L–1, providing potentials for fluorescence detection of cyt-c as well as facilitating intracellular cyt-c imaging.