Excited Oxidized-Carbon Nanodots Induced by Ozone from Low-Temperature Plasma to Initiate Strong Chemiluminescence for Fast Discrimination of Metal Ions

Carbon nanodots (C-dots) are recently well examined due to the emissions with color-tuning and nonblinking properties, while more studies are still needed for the appropriate understanding and application of distinct emissions. In this work, we found the emission of chemiluminescence (CL) by introducing low-temperature plasma (LTP) into C-dots solutions without any reagent added, whose intensity was affected by the presence of different metal ions. Based on both experimental data and theoretical calculations, we found with the ozonation by ozone from LTP, excited oxidized-C-dots would be generated with the addition of ozone onto the conjugated double bonds of C-dots, and these excited species could directly initiate strong CL combining with the deactivation of excited species to the ground state. Significantly, the cross-reactive CL signals were obtained from different kinds of C-dots with the presence of different metal ions. Therefore, a new sensor array (electronic tongue) composed of five different C-dots was designed for fast discrimination of metal ions, which achieved the accurate discrimination of 13 kinds of metal ions in pure water and real samples. It exhibited good reproducibility and sensitivity, which can be used for the quantitative analysis of metal ions such as showing a linear range from 4 x 10(-7) to 6 x 10(-5) mol.L-1 (R-2 > 0.99) for Fe3+ with a detection limit of 2.5 x 10(-7) mol.L-1. This work not only provides a novel finding of CL from C-dots revealing explicit relationship between structures and CL properties, but also realizes the fast discrimination of metal ions, showing potentials in environmental monitoring and quality identifications.