Sustainable Long‐Living Afterglow From a Natural Polyphenol Embedded in Urea‐Formaldehyde Resin

ABSTRACT

Room‐temperature phosphorescent (RTP) materials have attracted considerable attention for optoelectronics and anti‐counterfeiting, but developing sustainable, high‐performance RTP systems from natural resources remains challenging. Here we report a strategy to achieve long‐lived afterglow by embedding ellagic acid (EA) into a urea‐formaldehyde (UF) resin matrix. The EA/UF composite exhibits green RTP emission with a lifetime of 984.2 ms. Mechanistic studies reveal that the restricted carbonyl moieties of EA and the formation of a compact crosslinked network with UF promote spin‐orbit coupling and stabilize triplet excitons. By incorporating rhodamine B (RhB), red afterglow was achieved through a triplet‐to‐singlet Förster resonance energy transfer (TS‐FRET) mechanism. This strategy is universal: tannic acid, gallic acid, caffeic acid, and vanillic acid can all be converted into afterglow RTP materials in the UF matrix. As proof‐of‐concept, EA/UF was used for latent fingerprint imaging, time‐resolved anti‐counterfeiting, and 3D shaping. This work provides a sustainable platform for activating long‐lived afterglow RTP from renewable natural polyphenols.