Preparation of multicolor carbon quantum dots by hydrothermal method and their functionalization applications

Carbon quantum dots (CQDs) have become a popular research topic because of their many unique virtues, especially the significance of tunable photoluminescence properties. However, the synthesis of multicolor CQDs is still at an exploratory stage, and there are many dilemmas that have not yet been well resolved, such as long-wavelength emission and solid-state luminescence. Here, we selected suitable carbon and dopant sources as precursors for the synthesis of CQDs through the rational design of the experiments in an aqueous system, and the as-prepared CQDs possessed blue, green, yellow and red emissions, with optimal emissions of approximately 475 nm, 530 nm, 580 nm, and 645 nm, respectively. Furthermore, the corresponding PLQYs were 30.13 %, 36.84 %, 39.16 % and 21.36 %, respectively. It was found that the redshift of the emission wavelengths can be attributed to the synergistic effect of the increase in the sp2 conjugate size and the surface states. To conquer the aggregation caused quenching (ACQ) of CQDs and realize the solid-state luminescence of CQDs, we successfully prepared solid-state fluorescent films and solid-state phosphors. Finally, multicolor CQDs were successfully applied to prepare monochromatic and white light-emitting diodes (WLEDs). The adopted green synthesis technology can provide a good technical support for the future development of CQDs synthesis.