Facile preparation of carbon dots with multicolor emission for fluorescence detection of ascorbic acid, glutathione and moisture content

The nitrogen-doped carbon dots (N-CDs) with multicolor emission (green, yellow, and red) were fabricated with naphthalenetetracarboxylic dianhydride as carbon precursor, and different alkylamines as passive agents. The structures of the as-prepared carbon dots were confirmed by the Fourier transform infrared (FT-IR) spectrum, X-ray photoelectron spectroscopy (XPS) spectra, transmission electron microscopy (TEM), Raman spectra, and X-ray diffraction (XRD) pattern. The characterized results and UV–vis absorption spectrum demonstrated that the luminescence variations of different CDs were probably attributed to the difference of N-related states, oxygen-containing groups, and oxidation degree in the CDs structure. Moreover, the green emitting CDs (G-CDs) could be utilized as fluorescent probe for ascorbic acid (AA) detection with detection limit (LOD) of 5 μM. The yellow emitting CDs (Y-CDs) could be used to detect glutathione (GSH) in the range of 1–70 μM with LOD of 0.07 μM. The red emitting CDs (R-CDs) could detect the water content in THF, DMF, acetone, and EtOH with LODs of 0.44%, 0.31%, 0.55% and 0.55%, respectively. Remarkably, G-CDs and Y-CDs can distinguish AA and GSH respectively with high selectivity and accuracy. Finally, the fluorescent probes based on G-CDs and Y-CDs were successfully applied for the AA and GSH determination in vitamin C tablet, grapefruit juice, and GSH whitening serum samples with high reliability and feasibility, which provided the guidance for the selection of AA and GSH supplements.