Nitrogen-doped carbon dots with bright fluorescence for highly sensitive detection of Fe3+ in environmental waters

In this study, we synthesized stable nitrogen-doped carbon dots by a simple and economical one-step hydrothermal method using l-cysteine and anhydrous ethylenediamine as precursors. The prepared carbon dots have bright and stable blue light emission near 383 nm and can be used as fluorescent probes to detect the concentration of Fe3+ in environmental waters. It was demonstrated that due to intermolecular electrostatic interaction, a non-fluorescent complex N-CDs/Fe3+ is formed by coordination of Fe3+ with amino and carboxyl functional groups on the surface of carbon dots. Therefore, in combination with internal filtration effect, the fluorescence of carbon dots can be quenched in the presence of Fe3+, and the degree of quenching is linearly related to the concentration of Fe3+. The limit of detection in deionized water was as low as 0.069 μM with R2 of 0.998 and a linear range of 0.3 to 20 μM. In addition, satisfactory recoveries were achieved for the determination of Fe3+ in environmental water samples. The method is reliable, with highly sensitivity and selectivity, and has potential for practical applications in environmental metal analysis.