One-step electrolytic synthesis of nitrogen-doped carbon dots using graphite electrode in ionic liquid and their LED applications

Abstract

Carbon dots (CDs) possess unique optical properties, showing great potential for applications in optical imaging, detection and light-emitting diodes (LEDs). However, traditional synthetic methods usually adopt intense reaction, including hydrothermal and solvothermal methods, which inhibited the production and application of CDs. In this work, CDs were prepared via an electrochemical method utilizing graphite as the electrode and 1-butyl-3-methylimidazole chloride salt ([BMIM]Cl), an ionic liquid, as the electrolyte. This method is safe, controllable, and easy to operate under mild conditions. Three CDs with sizes of 2.98, 3.43, and 5.92 nm were synthesized by varying electrode materials (graphite and Pt wire). HRTEM images showed crystalline graphite structures with clear two-dimensional lattice fringes. Their chemical composition was further analyzed using XPS, FT-IR, and Raman spectroscopy. Their optical properties were evaluated through fluorescence, UV-Vis, and decay curves. CDs prepared with graphite as both electrodes showed a redshifted optimal excitation/emission wavelength (390/475 nm) compared to those with graphite as the anode and Pt as the cathode (320/425 nm). Furthermore, the luminescence and formation of these CDs were revealed. At last, these CDs were successfully applied in LEDs. This electrochemical approach provides a promising foundation for the preparation of CDs and their subsequent applications in LEDs.