Preparation of Nitrogen-doped Carbon Dots from Coke Powder as a Fluorescent Chemosensor for Selective and Sensitive Detection of Cr (VI)

The nitrogen-doped carbon dots (N-CDs) were prepared by using coke powder as carbon source and one-step hydrothermal method. The N-CDs were studied as a fluorescent chemosensor for determining Cr(VI) in water. The selective, sensitive, reproducibility and stability of as-prepared N-CDs were investigated. The morphology, composition and properties of N-CDs were characterized by a series of methods. The fluorescence quenching of N-CDs by Cr(VI) was explored. The experimental results reveal that the obtained N-CDs have great hydrophilicity and strong luminescence properties, which demonstrates the successful doping of nitrogen into the CDs. The surface-active groups and emission wavelength range of CDs increase due to the electronegativity and electron donor effect of doping N atom. Furthermore, the N-CDs exhibit good photochemical properties for the detection of Cr(VI), including a wide linear range from 0.3 to 200 µM (R2=0.9935) and a low detection limit of 0.10 µM at the signal-to-noise ratio of 3 (S/N=3). Moreover, the N-CDs as a sensor was used successfully for Cr (VI) detection in real water samples with recovery rates of 99.9%–110.6%. This sensor also shows highly reproducibility and stability. The N-CDs fluorescent chemical sensor may be a potential candidate for applying in the field of other fluorescent chemical sensing, catalysis, photoelectric devices and other fields.