Nitrogen doped carbon dots for sensitive detection of permanganate and hydrazine by a fluorescence off-on strategy

In this work, nitrogen doped carbon dots (N-CDs) were synthesized through one step hydrothermal reaction using ginkgo fruit and ethylenediamine as precursors. The luminescence of the N-CDs was speculated to be related with the electron transition of C=N bonds derived from grafting amines groups onto the the functional groups on the surface. MnO₄⁻ could selectively quench the fluorescence of N-CDs due to the formation of N-CDs-MnO₄⁻ complex on the surface. The linear relation between quenching efficiency and MnO₄⁻ concentration ranged from 1 to 60 µmol/L with a detection limit of 0.64 µmol/L. In the presence of hydrazine (N₂H₄), MnO₄⁻ was reduced to Mn²⁺ and the fluorescence of carbon dots was recovered. Results indicated that it can act as a secondary fluorescent probe for quantitative analysis of N₂H₄ in the scope of 0.5 to 14 µmol/L with a detection limit of 0.384 µmol/L. The N-CDs were successfully applied to analyze MnO₄⁻ and N₂H₄ in real samples with satisfactory recoveries (97.34-104.0% and 97.56-104.4%, respectively), implying good applicability in practical analysis.