Preparation of Nitrogen-Doped Carbon Quantum Dots and their Application in Detecting Heavy Metal Ions in Polymetallic Deposits

Nitrogen-doped carbon quantum dots (N-CQDs) were prepared by a one-step hydrothermal method using urea, aniline, and ethylenediamine as raw materials and nitrogen sources which exhibited good fluorescence performance. Spectral characteristics of the samples were analyzed using UV spectrophotometry, fluorescence spectrophotometry, and Fourier transform infrared spectroscopy. Optimal conditions, such as pH, reaction time, and ion concentration were investigated for N-CQDs. Under the optimal conditions (40 μL N-CQDs, buffer solution at pH 6 with a reaction time of 30 min), it was observed that cobalt ions caused a significant fluorescence quenching effect on the prepared N-CQDs, as determined by fluorescence spectrophotometry. The spiked recovery rates ranged from 95.8 to 104.6%, indicating that the N-CQDs could serve as a fluorescent probe for detecting the content of Co(II) in the actual environment. This method could be applied to the monitoring of heavy metal pollution in mine groundwater, the detection results of Co(II) using this method were very similar to ICP-MS, indicating that this method had good application prospects.