Highly crystalline graphitic carbon nitride quantum dots as a fluorescent probe for detection of Fe(III) via an innner filter effect.

Bulk g-C3N4 was transformed into water-soluble graphitic carbon nitride quantum dots (g-CNQDs) via a chemical oxidation and liquid exfoliation process. The g-CNQDs possess a size distribution ranging from 1 to 5 nm (centered at 3 nm), excellent crystallinity, and are water soluble. It is found that Fe(III) ions are adsorbed on the surface of the g-CNQDs via electrostatic interaction, and that the blue fluorescence of the g-CNQDs is reduced by Fe(III) via an inner filter effect. By using the g-CNQDs as a fluorescent probe, Fe(III) can be determined at excitation/emission wavelengths of 241/368 nm in spiked natural water samples within 1 min and with good selectivity over other ions. Response is linear in the 0.2-60 μmol·L-1 Fe(III) concentration range, and the detection limit is 23 nmol·L-1. Graphical abstract Graphitic carbon nitride quantum dots (g-CNQDs) emit blue fluorescence at an excitation wavelength of 241 nm. Fe(III) ions are quickly adsorbed on the g-CNQDs via electrostatic interaction, and fluorescence is quenched due to an inner filter effect.