Investigation of the luminescence mechanism of multi-color nitrogen-doped carbon quantum dots and their application in the detection of Fe3+.

This study reports the successful preparation of nitrogen-doped carbon quantum dots (N-CQDs) with a quantum yield of 15 % utilizing the hydrothermal method. Citric acid was employed as the carbon source, while 1,3-Diamino-2-propanol was utilized as the dopant. It was discovered that the emission of synthesized N-CQDs was dependent on concentration and excitation. By altering the N-CQDs concentration, the fluorescence emission peak was shifted from 453 to 574 nm, causing the emission to transition from blue to orange. The presence of multiple fluorescence emission centers within N-CQDs was confirmed through two-dimensional fluorescence matrix scanning. As the concentration of N-CQDs increased, the distance between these centers decreased, ultimately leading to aggregation. The energy or electrons were transferred as a result of the surface functional groups' interaction, which ultimately causes the fluorescence emission peak to shift to the red. Furthermore, an increase in concentration results in the formation of larger aggregates and larger sp2 carbon domains, ultimately resulting in longer wavelengths. Because of the convenience of use, high sensitivity, and rapid response of the fluorescent probe detection approach, multi-color N-CQDs with tunable concentration were used for the identification of Fe3+, with a 10–200 μM linear detection range and limits of detection (LOD) of 0.56 μM. [Display omitted] • N-CQDs exhibiting excitation-dependent and concentration-dependent emission were synthesized through the hydrothermal method. • Upon increasing the concentration of N-CQDs, a significant red shift was detected. The N-CQDs exhibited multiple FL centers. • Multi-color N-CQDs exhibited stability and have been effectively utilized for detecting Fe3+ with a LOD of 0.56 μM. [ABSTRACT FROM AUTHOR]