Boric Acid-Catalyzed Synthesis: A scalable strategy for High-Yield and Tunable red fluorescent carbon dots.

Red fluorescent carbon dots (RCDs) have garnered significant attention in the fields of lighting and bioimaging due to their exceptional optical properties and favorable biocompatibility. However, existing synthesis strategies often involve complex processes and rely on expensive, toxic polycyclic aromatic hydrocarbons, which fundamentally limit their yield and applicability. In this study, RCDs with a high quantum yield of 45 % were synthesized via a one-step solvothermal method using citric acid and urea as precursors, with boric acid as a catalyst. The introduction of boric acid induced a red shift in the fluorescence emission wavelength of the carbon dots from 468 nm to 651 nm. The yield of high-purity RCDs extracted from the crude product increased from 1 % to 55.4 %, and they could be easily separated via centrifugation. These RCDs significantly enhanced the color rendering performance of white light-emitting diodes (LEDs) and demonstrated satisfactory biocompatibility for cell imaging applications. Notably, the catalytic activity of boric acid was also observed in the synthesis of RCDs from other precursors, resulting in varying degrees of red shift in the fluorescence emission wavelength. This study establishes a foundation for environmentally sustainable, cost-effective, and scalable synthesis of RCDs.