A novel “turn-off” fluorescent sensor based on cranberry derived carbon dots to detect iron (III) and hypochlorite ions

A novel fluorescent carbon dots (CDs) have been prepared for the quantitative determination of iron(III) (Fe3+) and hypochlorite (ClO−) ions separately. Firstly, CDs were successfully synthesized using a hydrothermal treatment which is a green and simple method from cranberry as a novel natural resource. They were precisely characterized using advanced instruments. Secondly, CDs were separately studied by absorption and fluorescence spectroscopy as a fluorescence sensor for various metal cations and anions, respectively. As a result of spectroscopic data, it was showed that CDs were effectively quenched with Fe3+ ions among various cations and ClO− ions among various anions, respectively. The fluorescence intensities of CDs were quenched by forming a non-radiative complex between Fe3+ and CDs, and LOD for Fe3+ was calculated as 0.75 nM in the range of 1.6 nM to 22.8 nM. Furthermore, their fluorescence intensities are quenched by oxidizing of the hydroxyl groups on surface of CDs with ClO− ions, which have strong oxidant properties, and a detection limit (LOD) for ClO− was calculated as 1.60 nM in the range of 9.9 nM to 78.0 nM. Also, the proposed method to detect Fe3+ and ClO− ions was successfully applied in real natural spring and tap water samples. All data showed that these novel CDs could be used as a highly selective and sensitive, and instantaneously responsive "turn-off" fluorescence sensor for Fe3+ and ClO− ions.