How do nitrogen-doped carbon dots generate from molecular precursors? An investigation of the formation mechanism and a solution-based large-scale synthesis

• Published in: Journal of materials chemistry. B, Materials for biology and medicine Materials for biology and medicine, 2015-07, Vol.3 (27), p.5608-5614
• Main Authors: Hu, Yaoping, Yang, Jing, Tian, Jiangwei, Yu, Jun-Sheng
• Format: Article
• Language: English
• Subjects: Carbon; Fluorescence; Formations; Nanoparticles; Polymerization; Precursors; Spectroscopy; Synthesis
• ISSN: 2050-750X; 2050-7518
• DOI: 10.1039/c5tb01005e

A bottom-up method, using monoethanolamine (MEA) as both a passivation agent and a solvent, has been developed for rapid and massive synthesis of nitrogen-doped carbon dots (N-C-dots) from citric acid under heating conditions. This method requires a relatively mild temperature (170 °C) without special equipment, and affords one-pot large-scale production (39.96 g) of high-quality N-C-dots (quantum yield of 40.3%) in a few minutes (10 minutes). Significantly, an interesting formation process of N-C-dots, for the first time, has been monitored by transmission electron microscopy, ultraviolet-visible absorbance spectroscopy, photoluminescence spectroscopy, Fourier transformed infrared spectroscopy, and thermogravimetric analysis, and a corresponding formation mechanism, including polymerization, aromatization, nucleation, and growth, is proposed. It is important that the MEA-based synthesis of N-C-dots can be extended to various precursors, such as glucose, ascorbic acid, cysteine, and glutathione, which show general universality. Furthermore, the N-C-dots with strong fluorescence, excellent optical stability, and low cytotoxicity are successfully applied as fluorescent probes for bioimaging.