Hydrothermal Synthesis of Polyethyleneimine Modified Carbon Quantum Dots for Sensitively Detection of Cobalt Ions

In this work, fluorescent carbon quantum dots (CQDs) was prepared using natural on ions as carbon source with hydrothermal method and it was modified with polyethyleneimine (PEI). The properties of PEI modified CQDs (PEI-CQDs) were characterized by fluorescence, infrared spectroscopy and ultraviolet method, the morphology characteristics of PEI-CQDs was observed by transmission electron microscope. The results shown that the fluorescence excitation and emission wavelength were at 340 nm/462 nm, respectively. The fluorescence quantum yield was 8.68%, the average diameter of the PEI-CQDs was 2.82 nm. The infrared showed that the PEI-CQDs contained hydroxyl and amino groups on its surface. The Co²⁺ has selective quenching effects on fluorescence of PEICQDs, PEI-CQDs can be used for detection and analysis of Co²⁺ in samples. The limit of detection and linear range of Co²⁺ using the PEI-CQDs as fluorescence probe are 0.048 μM and 0.05–11 μM, respectively. The recovery was in the range of 97.00–100.64%. Moreover, the PEI-CQDs are also successfully utilized for monitoring the Co²⁺ content of tap water.