Synthesis of diethylenetriamine-modified carbon quantum dots for dual sensing Fe3+and Co2+and its application

Surface modification is an important method for regulating the carbon quantum dots structure and enhancing the performance. Herein, green fluorescent carbon quantum dots (G-CQDs) were synthesized by the solvothermal method using p-phenylenediamine as carbon source, diethylenetriamine as modifier and anhydrous ethanol as solvent. G-CQDs were characterized by TEM, FTIR, XPS, UV-Vis absorption spectroscopy, fluorescence spectroscopy and Zeta potential. The particle size of G-CQDs was about 2.11 nm and the fluorescence quantum yield of G-CQDs was increased from 1.07 % to 28.90 % after diethylenetriamine modification. The increase of nitrogen and oxygen contents after modification enriches the oxygen-containing and nitrogen-containing groups on the surface, providing more reaction sites for metal ions. It was further found that G-CQDs can detect Fe3+ and Co2+ based on two different fluorescence "on-off" mechanisms with detection limits of 0.88 mu M and 0.95 mu M, respectively. In practical applications, the excellent fluorescence performance of G-CQDs for information anticounterfeiting has a good effect. It was used for the detection of Fe3+ and Co2+ in tap water, the spike recovery were in the range of 98.11 % - 106.80 % and 95.87 % - 104.49 %, respectively, showing good accuracy and reproducibility.