One-step Hydrothermal Synthesis of Nitrogen-doped Carbon Quantum Dots with Escherichia Coli for Selective Detection of Ferric Ion

Nitrogen-doped carbon quantum dots ( N-CQDs ) with good water solubility, pH stability and salt tolerance were synthesized by hydrothermal method (180 degrees C ) with Escherichia coli as precursor. The structure of N-CQD was characterized by transmission electron microscopy, dynamic light scattering, and Fourier transform infrared spectroscopy. The results showed that the particle size was uniform with a diameter of 4. 1 nm , the dispersibility was good, and the surface contained a large amount of hydrophilic groups. UV-visible absorption and fluorescence spectra were used to study optical properties , and it was found that Fe3+ could selectively quench the N-CQDs fluorescence. In the concentration range of 0.58 nmol/L-100 mu moUL , the quenching degree had a good linear relationship with the concentration of Fe3+ ion. The detection limit was 0.58 nmo/L, and the recoveries were 93. 9% -108. 7%. At the same time, the interference of pH, salt content and coexistence metal ion on Fe3+ determination was studied. The results showed that the method was especially suitable for selective fluorescent detection of Fe3+ in offshore seawater with high salt content, large range of pH and diverse metal ions.