Tailoring the Emission of Carbon Dots via Solvent Engineering for White Light-Emitting Diodes and Anticounterfeiting

Multicolor emissive carbon dots (CDs) are being investigated as a sustainable substitute for conventional phosphor-based white light-emitting diodes, which are challenged by issues including high cost and low color stability. Here, a new approach is introduced to multicolor emissive CDs in a single reaction system. At first, we used a solvothermal treatment to develop yellow-emitting CDs. After that, the solvent engineering process is adopted to develop orange and green emissive CDs. Additional investigation shows that the orange and green shifting are mostly caused by different surface states arising due to hydrogen bonding (H-bonding) formation. The X-ray photoemission spectroscopy analysis exhibited that orange CDs had more semi-ionic C-F bonds and ionic fluorine states than their yellow and green equivalents. Fluorine functionalities play a key role in emission color adjustment by stabilizing surface imperfections and modulating radiative pathways through strong hydrogen bonding interactions. Finally, we attained white LEDs by combining the orange and green emissive films over the LED chip, showing a correlated color temperature of 6409 K and a high color rendering index of 92. Remarkably, the as-synthesized CDs exhibited room-temperature phosphorescence, allowing us to use them for anticounterfeiting and latent fingerprint applications. Due to its ease of use, affordability, and environmental friendliness, this method holds promise for creating multicolored CDs and could encourage their use in optoelectronics and forensic research.