Convenient Production of Photothermal Recycling Phosphorescent Materials from Cellulose and Lignin.

Developing recyclable room-temperature phosphorescent (RTP) films using ultrafast fabrication techniques remains a critical yet challenging objective. With this research, we developed an RTP film (Cell-Lig) through ethanol-induced phase transition, achieving solid film formation within 1 s from ionic liquid (1-butyl-3-methylimidazolium chloride, [Bmim]Cl) solutions of cellulose and lignin. The phase transition also generated a confined rigid environment for Cell-Lig, activating thickness- and temperature-dependent green RTP emission from the incorporated lignin. Furthermore, red afterglow emission using an energy transfer mechanism was realized by incorporating rhodamine B (RhB). The inherent photothermal activity of lignin endowed Cell-Lig with easy recyclability using light-controlled phase transitions. Under irradiation, photothermal evaporation of residual ethanol triggered liquefaction (solid-to-liquid transition), while ethanol reintroduction facilitated instantaneous hardening. Remarkably, the initial RTP performance was maintained over six recycling cycles. Capitalizing on these attributes, Cell-Lig was successfully used for advanced coating and security applications.