Chemiluminescence of Nitrogen-Doped Carbon Quantum Dots for the Determination of Thiourea and Tannic Acid

Water-soluble nitrogen-doped carbon quantum dots (NCD) were prepared via a facile and green ultrasonic process. It was found that KMnO4/Ce(IV) could directly oxidize NCD to produce chemiluminescence (CL) emission. Further investigation indicated that the CL intensity of NCD-KMnO4 system was obviously increased in the presence of thiourea (TU) or tannic acid (TA). Under the optimum conditions, the enhanced CL intensity was linearly proportional to the concentration of TU in the range of 0.1 to 10.0 μM with a detection limit of 0.038 μM and TA in the range from 0.07 to 7.0 μM with a detection limit of 0.026 μM. The method has been applied to the determination of trace TU in the orange juice and orange peel and TA in the Chinese gall with satisfactory results. Moreover, the mechanism of CL generation was investigated by the kinetic curves, the spectra of the CL, the fluorescence, and the UV-vis.