A Universal Gd³⁺-based hydrogel matrix for inducing room-temperature phosphorescence

Room-temperature phosphorescence (RTP) is difficult to achieve in aqueous media, due to the inherent and serious quenching of the excited triplet states by O₂ and H₂O. Herein, we report RTP induction enabled by a hydrogel matrix assembled from Gd³⁺ and adenosine monophosphate (AMP). Benefiting from the promoted intersystem crossing (ISC), effective guest confinement, and excellent oxygen shielding, the Gd³⁺-AMP hydrogel permitted efficient RTP emission from guest molecules. Notably, second-scale afterglow (>1 s) was observed from the thioflavin T (ThT)-encapsulated hydrogel, which has rarely been reported for ThT, confirming the high efficiency of the hydrogel matrix. Moreover, the matrix could efficiently encapsulate diverse guest molecules without size or charge restrictions through an adaptive encapsulation process, thus serving as a universal RTP matrix. Leveraging the stimuli-responsive, shear-thinning, and biocompatible properties of the hydrogel, single- and co-encapsulated RTP systems were further applied in bioimaging, three-dimensional (3D) encoding, and color-tunable white-light emission.