Carbon dots tailored with a fluorophore for sensitive and selective detection of hydrogen sulfide based on a ratiometric fluorescence signal

Abstract

To discriminate hydrogen sulfide (H₂S) from thiol nucleophiles with similar reactivity is always a major challenge in developing new detection methods. In this paper, we report a colorimetric and ratiometric fluorescence probe selectively reactive to H₂S, which was synthesized by hybridizing the fluorescent nitro-benz-2-oxa-1,3-diazole (NBD)-based derivative P-NBD with carbon dots (CDs). The selective reaction can be monitored by distinct ratiometric fluorescence or colorimetric variation. The nanohybrid probe exhibited two fluorescence bands centered at 440 nm and 543 nm, respectively. The yellow fluorescence at 543 nm from P-NBD is quenched by H₂S, while the blue fluorescence is enhanced by weakening of the Förster resonance energy transfer (FRET) mechanism. It was observed that the apparent fluorescence color evolved from yellow to blue when exposed to different amounts of H₂S, accompanied by the color change of the probe solution from yellow to red under natural light. The detection limit was estimated to be 57 nM in aqueous solution. We successfully applied this probe for the detection of H₂S in real water samples, suggesting its potential application in environmental monitoring and protection.