Preparation of fluorescent nitrogen-doped carbon dots for highly selective on-off detection of Fe3+ ions in real samples

In this work, nitrogen-doped carbon dots (N-CDs) based fluorescent probes were synthesized using m-phenylenediamine and citric acid as both nitrogen and carbon source through the hydrothermal method. The structural and optical properties of synthesized N-CDs were investigated by transmission electron microscopy (TEM), dynamic light scattering (DLS), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), UV–vis spectroscopy, Zeta potential, and photoluminescence (PL). The water-soluble N-CDs showed a narrow size distribution within 6–8 nm. The emission peak with maximum intensity for N-CDs was 535 nm at the excitation wavelength of 470 nm, and the quantum yield of N-CDs was 30.2%. The as-prepared N-CDs could be selectively quenched by Fe3+ ions with a limit of detection (LOD) of 13.8 nM in a linear range from 0.002 μM to 8 μM. Furthermore, examining the validity of the present fluorescence N-CDs probe showed that the proposed method has enough reliability and sensitivity for detecting Fe3+ ions in an acceptable recovery range from 97 to 106.4% in the real samples. The probe indicated high stability and selectivity to be a suitable candidate for environmental applications.