Nitrogen and sulfur co-doped carbon dots: A facile and green fluorescence probe for free chlorine

• A sensitive and green fluorescence probe was developed for the detection of free chlorine.
• The assay was based on fluorescence quenching of nitrogen and sulfur co-doped carbon dots.
• The assay is high sensitivity and selectivity for detection of free chlorine in tap water.

Nitrogen and sulfur co-doped carbon dots (N,S-CDs) emitted strong blue fluorescence in aqueous solution, and it was found that the free chlorine could efficiently quench the fluorescence of the N,S-CDs, which was utilized as a sensitive, low-cost and green fluorescence probe for the detection of free chlorine. Under optimal conditions, a linear relationship between the decreased fluorescence intensity of N,S-CDs and the concentration of free chlorine in the range from 0.01 to 100 μM was obtained with a detection limit of 5 nM (3σ). The proposed method was successfully applied for the determination of free residual chlorine in tap water and swimming pool with quantitative recovery (91–106%). The developed N,S-CDs fluorescence probe provides a new and promising tool for the water quality monitoring in the environmental analysis fields with low cost and excellent performance.

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