Highly fluorescent carbon dots synthesized with binary dopants for “turn off” and “turn off-on” sensing and cell imaging

• Published in: Sensors and actuators. B, Chemical Vol. 268; pp. 84 - 92
• Main Authors: Li, Lu-Shuang, Jiao, Xin-Yue, Zhang, Yu, Cheng, Cheng, Huang, Kun, Xu, Li
• Format: Journal Article
• Language: English
• Published: Lausanne Elsevier B.V 01.09.2018; Elsevier Science Ltd
• Subjects: Aldehydes; Binary dopants; Biosensors; Carbon; Carbon dots; Citric acid; Cytotoxicity; Dopants; Drinking water; Fluorescence; Formaldehyde; Ions; Melamine; Mercury (metal); Quenching; Sensor; Tablets; Toxicity; Turn off; Turn off-on; Turn off-on; Carbon dots; Turn off; Binary dopants; Sensor
• ISSN: 0925-4005; 1873-3077
• DOI: 10.1016/j.snb.2018.03.189

[Display omitted] •Melamine and formaldehyde were the binary dopant to produce carbon dots (CDs).•High quantum yield of the CDs up to 48% was obtained.•Two “turn off” sensing systems were established to detect Hg2+ and ClO−.•Two “turn off-on” sensing systems were established to detect halogen ions and Fe2+.•The CDs with low cytotoxicity were successful for cellular labeling on HepG2 cells. In the present study, highly fluorescent carbon dots were prepared by using citric acid as the carbon source with the binary dopants, i.e. melamine and formaldehyde, named as MF-CDs. The co-dopants played a crucial role to enhance the fluorescence quantum yield of the MF-CDs, reaching 48%, in which melamine was the major nitrogen source, while formaldehyde was the co-dopant to regulate the state of nitrogen in the MF-CDs. The fluorescence of the MF-CDs was found to be quenched by Hg2+, and then recovered equally by individual halogen ions (eg. Cl−, Br− and I−). Correspondingly, the “turn off” and “turn off-on” sensing systems were separately established to detect Hg2+ and total halogen ions with good accuracy and reliability. In addition, the fluorescence of the MF-CDs was quenched by ClO−, and recovered by Fe2+; the “turn off” sensor was established to detect ClO− in tap water with low limit of detection of 0.18 μM, and the “turn off-on” sensor was to determine the ferrous succinate in ferrous succinate tablets. Furthermore, owing to the low cytotoxicity, the MF-CDs were successful for cellular labeling on HepG2 cells. The developed binary dopants were effective to enhance the fluorescence quantum yield and endow the MF-CDs with some special properties, which would help to widen the applicability of the carbon dots.