Preparation of Carbon Dots with High Fluorescence Quantum Yields and its Detection of Hg in Simulated Wastewater.

Fluorescent carbon quantum dots (CDs) have received widespread attention for their potential applications in optical sensing. Meanwhile, as the importance of mercury ion (Hg) detection in the environment, the exploration of Hg fluorescent nanosensor based on CDs with high quantum yield is particularly intriguing. Herein, nitrogen-doped carbon quantum dots (N-CDs) were prepared by microwave method using citric acid as carbon source and urea as nitrogen source, and glycerol as microwave solvent. The N-CDs were characterized by transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD) technique, Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). The fluorescence quantum yield of the N-CDs is calculated to be as high as 60.51%. The N-CDs can specifically recognize Hg, and there exists a strong linear correlation between the concentration of Hg and the fluorescence quenching intensity of N-CDs. The linear equation is F/F = 0.0062c + 1.5532, R = 0.9936, and the detection limit is 0.080 µmol/L. The experimental results show that the recovery rate of Hg in simulated wastewater ranges from 97 to 102%, and the relative standard deviation (RSD) is less than 3%, indicating that the prepared N-CDs can be used as a fluorescent probe for accurate detection of Hg.