Nitrogen doped carbon quantum dots (N-CQDs) with high luminescence for sensitive and selective detection of hypochlorite ions by fluorescence quenching

A highly luminescent nitrogen-doped carbon quantum dots (N-CQDs) with a quantum yield of 44% was prepared by a facile hydrothermal synthesis method using citric acid (CA) and ethylenediamine (EDA) with a molar ratio of 1:1 at 200 degrees C for 5 h. The hypochlorite (ClO- ) ions significantly quench the fluorescence of the N-CQDs according to a pseudo-second-order kinetic model. A sensitive and selective quantification method with an excellent linearity in the range of 1.0-10.0 mu M was developed to detect ClO- ions based on the fluorescence quenching. The limit of detection (LOD) of 0.43 mu M and the limit of quantification (LOQ) of 1.04 mu M were achieved, respectively. This approach was successfully applied to detect the residual ClO- ions in local tap water and in swimming pool water. In addition, the developed fluorescence quenching method was also successfully applied in anti-counterfeiting and paper encryption. Both of the applications in real world suggest that the asprepared N-CQDs is a kind of promising fluorescence probe for rapid detecting ClO- ions in environment fields, and has potential applications in text secrecy fields.