One-Pot Synthesis of Multicolor Carbon Dots from PET Plastic Waste for White Light-Emitting Diodes

Conversion of PET waste into carbon dots (CDs) is an attractive approach to plastic pollution control. However, the preparation of red–yellow CDs is still challenging, and the preparation methods are complex. In this study, a one-pot solvothermal method was developed for the preparation of CDs from PET waste. Through nitrogen source and solvent screening, multicolor (blue–red) CDs with high quantum yield (QY) were prepared. The reaction temperature and catalyst dosage significantly influence the production yield and QY of the CDs. The optimized CD showed a relative yield of 42.7%, a high QY of 47.8%, and a red photoluminescence color. The morphology, crystal structure, surface chemistry, and optical performance of CDs were characterized. The red and yellow fluorescence was mainly due to the molecular state mechanism. White light-emitting diodes with cool and warm white light and a high color rendering index were constructed using yellow and red CDs.