Strong acid-assisted preparation of green-emissive carbon dots for fluorometric imaging of pH variation in living cells
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New green-emissive carbon dots (G-CDs) are described here and shown to be viable fluorescent nanoprobes for the detection of changes in cellular pH values. By using m-phenylenediamine as the carbon source, G-CDs with an absolute quantum yield of 36% were solvothermally synthesized in the presence of strong H2SO4. The G-CDs have an average size of 2.3 nm and display strong fluorescence with excitation/emission peaks at 450/510 nm. The fluorescence intensity depends on the pH value in the range from 6.0 to 10.0, affording the capability for sensitive detection of intracellular pH variation. The nanosensor with excellent photostability exhibited good fluorescence reversibility in different pH solutions, and showed excellent stability against the influence of other biological species. The nanoprobe was successfully used in confocal fluorescence microscopy to determine pH values in SMMC-7721 cells.
KeywordsCarbon nanoparticles Nanoprobes m-Phenylenediamine Assistance of H2SO4 Fluorescence Quantum yield Excellent photostability Intracellular pH change Bioimaging Real-time sensing
The authors acknowledge the financial support by the National Natural Science Foundation of China (No. 21807068, 21373132, 21502109), the Natural Science Foundation of Shaanxi Province (No. 2017JQ2017), and the Project of Shaanxi University of Technology (SLGKY14-08).
Compliance with ethical standards
The author(s) declare that they have no competing interests.
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