Selective determination of free dissolved chlorine using nitrogen-doped carbon dots as a fluorescent probe

The authors report that nitrogen-doped carbon dots (N-CDs) represent a viable fluorescent probe for the determination of dissolved free chlorine. The N-CDs can be fairly easily prepared by a solvothermal method using citric acid, tartaric acid and ethanediamine as the precursors, display excitation/emission maxima of 360/460 nm, and have a quantum yield of 42.2 %. Free chlorine and ClO- quench fluorescence, and this was exploited to design a method for fluorometric determination of chlorine and hypochlorite. The probe has a short response time (< 1 min), excellent selectivity, high sensitivity, and a linear response range that extends from 0.1 to 27 mu M. The limit of detection is as low as 29.7 nM. The method was applied to the determination of chlorine dissolved in tap water.