Nitrogen-doped carbon dots with high quantum yield for colorimetric and fluorometric detection of ferric ions and in a fluorescent ink.

Nitrogen-doped carbon dots (N-CDs) with a quantum yield of 41 ± 3% and excellent stability were prepared and are shown to be viable probes for the determination of ferric ions, which is a strong quencher of fluorescence. The absorption peak of the N-CDs is located at 325 nm. The optimal excitation and emission wavelengths of the N-CDs are 340 nm and 430 nm, respectively. The fluorometric response to Fe(III) is linear in the ranges between 1.0 and 21.0 μM and between 0.05 and 30.0 μM, and the limits of detection are 0.28 μM in case of colorimetry and 13.5 nM in case of fluorometry. Quenching by Fe(III) is mainly attributed to a combination of chelation (static quenching) and inner filter effect. The N-CDs also can be used as a new sort of fluorescent ink owing to the strong luminous performance and chemical inertness. Graphic abstract The illustration for synthesis of the N-CDs and its applications for colorimetric and fluorescent detection of Fe3+ and fluorescent ink.