Biomass-derived white carbon dots: Green synthesis, multicolor separation, and applications in white LEDs and information encryption

Biomass-derived white-light-emitting carbon dots (W-CDs) show significant promise for eco-friendly optoelectronic applications. Herein, W-CDs were synthesized via a one-step solvothermal method using renewable Lygodium japonicum as the carbon source and o -phenylenediamine as the nitrogen dopant, a sustainable and low-cost approach aligning with green chemistry principles. Under 380 nm ultraviolet excitation, the aqueous W-CDs solution emitted bright white light, with Commission International de l'Eclairage (CIE) coordinates of (0.29, 0.34) and a relative quantum yield of 3.09%. Notably, four distinct fluorescent components were successfully isolated by thin-layer chromatography (TLC) from this single biomass system: indigo blue (I-CDs, λ em  = 410 nm), blue (B-CDs, λ em  = 460 nm), green (G-CDs, λ em  = 515 nm), and red (R-CDs, λ em  = 670 nm). Comprehensive characterization (XPS, FT-IR, TEM, etc.) confirmed that the multicolor photoluminescence primarily originates from carbon core states, where increased sp 2 -conjugated domains and graphitic nitrogen content induce emission redshift. The separated multicolor CDs exhibit excellent photostability and tunable emission, while W-CDs enabled the fabrication of white light-emitting diodes (W-LEDs) with a correlated color temperature (CCT) of 7338 K. This study offers novel insights into the multifunctional utilization of biomass-derived carbon dots, highlighting their promising applications in solid-state lighting and information security.