Kinetic Fluorimetric Determination of Iridium Based on the Catalytic Oxidation of Doped Carbon Dots

In this study, multi-element doped carbon dots (DXM-CDs) were synthesized via a one-step hydrothermal method, utilizing dexamethasone sodium phosphate (DXM) injection as a precursor. The synthesized DXM-CDs exhibited ultraviolet fluorescence emission at 380 nm, with a fluorescence quantum yield (QY) of 19.7%. The fluorescence intensity of DXM-CDs was quenched via oxidative degradation using KBrO₃ in H₃PO₄ medium. The presence of Ir⁴⁺ ion catalyzed the oxidation of DXM-CDs using KBrO₃, resulting in an accelerated fluorescence quenching. Based on this catalytic oxidation reaction, a kinetic fluorimetric method for the quantification of Ir⁴⁺ ions was developed. The optimum conditions obtained are 0.4 M H₃PO₄, 2.0 mg mL^- 1 of DXM-CDs, 1.0 mM KBrO₃, reaction temperature of 100 °C, and reaction time of 20 min. Under optimized conditions, the method achieved a detection limit (3σ) of 14 pg mL^- 1 and linear response was observed in the concentration range of 0.2 to 20 ng mL^- 1. The developed method was successfully applied to the determination of Ir⁴⁺ ions in water samples, yielding accurate and precise results.