Determination of multiple targets by using dual-fluorescence emissive carbon dots

There are various kinds of pollutants in our environment from the discharged sewage that damage human's health. Determination of multiple pollutants is important for safety and the detection methods are always needed. This study reports a determination method for p-nitrophenol ( p-np) and copper ions by using the dual fluorescence centers of N,S co-doped CDs (N,S-CDs). N,S-CDs was prepared by hydrothermal treatment of thiourea and cit-ric acid in N -N dimethylformamide. The as-prepared N,S-CDs are spherical particles with size distribution of 1.20 +/- 0.42 nm, as well as functional groups such as thiol and carboxyl. The rich surface species endow the CDs dual fluorescence centers at 380 nm/460 nm and 550 nm/625 nm. Interestingly, the fluorescence at 380 nm/460 nm can be quenched by p-np, while the fluorescence at 550/625 nm can be quenched by copper ions. Mechanism investigations revealed that inner filter effect of p-np and combination with copper ions are responsi-ble for the fluorescence quenching. Determination methods are thus found with detection limits of 6.47 x10-6 mol L -1 forp-np and 6.0 x10 -7 mol L -1 for Cu2+. Piped water are tested and the results are satisfactory with recoveries in the range of 94.33% -100.67% for p-np and 98.67% -106.33% for Cu2+. In conclusion, this work provides a new approach for determination of multiple targets by using the dual fluorescence of N,S-CDs.