Preparation of carbon quantum dots biofilm and adsorption of heavy metal Cu2+

Currently, seawater is seriously polluted by Cu2+, thus the development of safe and efficient Cu2+ removal materials is important for maintaining the safety of marine ecology. In this study, we utilized reed and urea as raw materials, synthesizing carbon quantum dots (CQDs) and nitrogen-doped carbon quantum dots (N-CQDs) through the hydrothermal method. Then, we analyzed their performance in Cu2+ detection and absorbance. Both the CQDs and N-CQDs exhibited excellent fluorescent properties, with maximum excitation wavelengths at 325 nm and corresponding emission wavelengths at 400 nm. Nitrogen doping enhanced the fluorescence intensity and stability of CQDs. Various metal ions were tested for their fluorescence-quenching effects on CQDs and N-CQDs. The results indicated that the N-CQDs exhibited strong adsorption capacity towards Cu2+, showing a good linear relationship at Cu2+ concentrations ranging from 0 to 50 μmol/L with a detection limit of 1.081 μmol/L. Additionally, we prepared a CQDs-biofilm using 3% chitosan as raw material and evaluated the adsorption of Cu2+ by the N-CQDs biofilm. The findings revealed that the Cu2+ adsorption rate of the N-CQD biofilm ranged from 28% to 67%. This CQD-biofilm is significant for trace detection and pollution control of Cu2+ in aqueous media.