Room-Temperature Phosphorescence Hydrogel with Multiple Color Based on Salt-Induced Aggregation

Organic photoluminescent materials with room-temperature phosphorescence (RTP) are of great interest, yet achieving RTP in hydrogels faces challenges due to water-quenching effects. In this study, a straightforward method is presented to achieve RTP hydrogel using a self-healing and salt-hardening hydrogel. The hydrogel is synthesized by polymerizing acrylic acid (AA) with diethylenetriamine (DETA) as the dynamic crosslinker. The poly(acrylic acid)/DETA hydrogel could achieve an afterglow lasting 1.6 s after soaking with NaBr solution. The salt-enhanced hydrophobic aggregation of the hydrogel network promotes the clustering of carboxyl groups and oxygen atoms, resulting in a rigid environment that suppresses nonradioactive transitions and leads to the manifestation of RTP. Additionally, the dynamic association of AA-DETA allows the freeze-dried hydrogel powder to be blended with various hydrophobic dyes, leading to a remodelable hydrogel with delayed emission of multiple colors. In general, by combining salt-hardening property with self-healing property together, a RTP hydrogel platform that can be facilely loaded with various organic dyes is proposed.