Preparation of Carbon Dots with High Thermal Stability and Their Fluorescent Films

Carbon dots (CDs) have been applied to solid lighting because of their excellent fluorescent properties, good chemical stability, easy functionalization, and other advantages. However, the low thermal stability of most CDs limits the wide application of CDs as phosphors in laser illumination field. Aiming at CDs with high thermal stability and low cost, Y-CDs with fluorescent quantum yield of 49% were prepared by one-step hydrothermal method using citric acid and 2，7-dihydroxynaphthalene as raw materials and adjusting the concentration of reactants. The YG-CDs after annealing only lost 10% of weight at 250 ℃, while their thermal stability was greatly improved. The fluorescent films with good transmittance, fluorescent property, and thermal stability were obtained by combining the annealed YG-CDs with three film-forming agents (polymethyl methacrylate, polyvinyl alcohol, and silane coupling agent). This research provides a theoretical and practical basis for the application of CDs-based fluorescent films for laser illumination.