Nitrogen and Sulfur-Doped Carbon Quantum Dots Used as Fluorescent Probes

Using hydrolyzed olive leaves as a carbon source and thiourea as a dopant, nitrogen-sulfur co-doped carbon quantum dots (NS-CQDs) were synthesized in the present work. The as-prepared NS-CQDs exhibited quasispherical morphology with an average particle size of 2–5 nm. Functional groups such as carboxyl and hydroxyl groups distributed on the surface of NS-CQDs were suggested to contribute to the good water solubility, biocompatibility, and strong fluorescence. Amphotericin B (AMB) was found to enhance the fluorescence intensity of NS-CQDs, whereas Fe(III) quenched the fluorescence of NS-CQDs. Taking advantage of such fluorescent characteristics, we established herein a quantitative method of measuring the content of AMB and Fe³⁺ in water, with detection limits of 10.0 and 7.4 μM, respectively.