Biomass-based thermally tunable dual afterglow with room temperature daylight visibility

Biomass-derived long-persistent afterglow materials that simultaneously deliver thermally activated delayed fluorescence (TADF) and room-temperature phosphorescence (RTP) are highly sought after but remain challenging to achieve, particularly when daylight-visible RTP and high-temperature-tolerant, color-tunable TADF are required. Herein, we develop a thermally tunable RTP-TADF dual-mode afterglow material featuring thermochromic green-to-blue emission by using boric acid (BA) to covalently crosslink natural ellagic acid (EA) and cellulose (Cell) in situ during a facile air-drying process. The resulting EA@Cell, with B-O-C-rigidified structural network, exhibits long-persistent green RTP that remains visible to the naked eye for up to 8 s under daylight conditions upon ultraviolet excitation. Notably, EA@Cell exhibits thermally enhanced TADF emission across 293-413 K, with a 127-fold increase in afterglow lifetime, and maintains its structural integrity and emissive robustness even at temperatures as high as 453 K. As a practical demonstration of EA@Cell, the solution of EA and BA is formulated into daylight-visible RTP inks and thermochromic afterglow inks, enabling low-cost cellulose-based anti-counterfeiting, high-temperature thermal sensing, and dynamic information encryption.