Facile Synthesis of Polyethylene Glycol Passivated N-doping CQDs as Fluorescent Probe for Multi-Target Simultaneous Detection in Heavy-Metals Solution.

In order to quickly and conveniently detect multiple heavy metal ions in aqueous phase simultaneously, a polyethylene glycol passivated N-doping carbon quantum (p-N-CQDs) was synthesized by a hydrothermal method with citric acid (carbon source), urea (nitrogen source) and polyethylene glycol (passivator). The as-prepared p-N-CQDs could be evenly dispersed in deionized water, and the average diameter was 1.83 nm, resulting in 18.72% of fluorescence quantum yield. As a sensor, the fluorescence of p-N-CQDs would be significantly quenched with Fe or Cu under the different maximum emission wavelength of 452 nm and 448 nm, respectively. Therefore, a method for simultaneously detecting multiple heavy metal ions was proposed by discriminative fitting of the fluorescence emission peaks after metal ion quenching. Upon the experiments, two linear calibration curves between resolving fluorescence intensities of p-N-CQDs and concentration of the metal ions were obtained within a range of 10 to 1000 µM of Cu and 40 to 800 µM of Fe. And a limit of detection (LOD) of 0.032 µM was attained after resolving the curves based on the emission wavelength of 448 nm for Cu and 452 nm for Fe by a peak splitting software. In addition, the stability, selectivity and anti-interference of the proposal senor was confirmed.