Facile synthesis of nitrogen-doped carbon dots and its application as sensing probes for serum iron

In this paper, nitrogen-doped carbon dots (N-CDs) with a quantum yield of 23.6 % were successfully synthesized by microwave pyrolysis of urea using diethylene glycol as the high boiling point reaction medium. The N-CDs were spherical and monodisperse with a size distribution between 1.5 and 5.5 nm. The N-CDs exhibited excellent water-soluble property and remarkable stability under extreme ionic strengths and light illumination. The fluorescence of the N-CDs could be quenched by Fe3+ through the static quenching mechanism, but not by other common metal ions. On this basis, the N-CDs can be used as a facile sensing platform for label-free sensitive and selective detection of Fe3+ in a linear range of 1.6–333.3 μmol L−1, and the detection limit was 0.45 μmol L−1 obtained at a signal-to-noise ratio of 3. Importantly, the N-CDs-based fluorescent probe was successfully applied to the direct analysis of iron contents in human serum samples, which demonstrated potential applications in biological and clinical analysis.