Confinement of carbon dots into carboxymethyl cellulose matrice to prepare solid-state fluorescent films and couple with Eu-MOF toward white light-emitting diodes.

As a novel fluorescent carbon nanomaterial, carbon dots are restricted by their poor fluorescence in the solid state, although they exhibit favorable photoluminescence in solution. N-doped carbon dots (N-CDs) and solid-state fluorescence films were prepared using green and renewable cellulose-derived materials, respectively. The hydrogen bonding network of carboxymethyl cellulose (CMC) inhibits the self-aggregation behavior of N-CDs, which leads to solid-state fluorescence. The N-CDs was initially obtained with CMC as the carbon source, which showed excellent blue fluorescence. Subsequently, the white-emitting films (N-CDs@Eu-MOF/CMC) were successfully constructed by combining the blue fluorescent N-CDs with the red fluorescence of the europium metal-organic framework. The prepared films showed stable luminescence within 30 days and in the heat environment at 120 °C for 3 h. After covering the N-CDs@Eu-MOF/CMC films on the UV-LED chip with ultraviolet emissive at 365 nm, the white light-emitting diodes were obtained, which exhibited excellent color characteristics with the color coordinates, a correlated color temperature, and a color rendering index of (0.31, 0.32), 6580 K, and 92, respectively. The strategy proposed in this work will provide ideas for generating optical luminescent films from biomass and provide guidance for solid-state fluorescence biomass materials.