Nitrogen-doped fluorescent carbon dots are used for ultra-sensitive detection of Co2+ and cell imaging

For the first time, nitrogen - doped carbon dots (N-CDs) with excellent properties were synthesized by hydrothermal method using honeysuckle as a carbon source and ethylenediamine as a nitrogen source. The prepared N-CDs have abundant functional groups, small particle sizes, good water solubility, excellent fluorescence performance, and high chemical stability. They can emit blight blue fluorescence under ultraviolet light. Using quinine sulfate as a reference, the fluorescence quantum yield of N - CDs was measured to be as high as 15.6%. Under optimal conditions, N-CDs could selectively detect Co2+, and the fluorescence intensity of N-CDs was linearly quenched by Co2+ in a range of 0.5 to 3.6 nmol center dot L-1, with a detection limit as low as 1.38 nmol center dot L-1. The quenching mechanism belongs to the internal filtering effect and static quenching. Therefore, an ultra-sensitive Co2+ detection method has been established. To further confirm the feasibility of this sensor, we have also successfully applied it to the precise analysis of Co2+ in tap water samples. In addition, N-CDs have been successfully used for cell imaging and intracellular Co2+ sensing due to their low cytotoxicity and good biocompatibility.