Stable Persistent Room-Temperature Phosphorescent Hydrogels Based on Ionically Crosslinked Nonaromatic Carboxylate Polymers

Developing pure organic room-temperature phosphorescent (RTP) hydrogels is important for expanding the practical applications of phosphorescent materials. However, most of the reported RTP hydrogels containing aromatic phosphors suffer from short phosphorescent lifetimes, unstable underwater RTP emissions, and complex preparation processes. Herein, novel nonaromatic RTP hydrogels are prepared by using two types of non-traditional luminescent polymers, sodium alginate and a polymeric carboxylate, which are not RTP emissive or very weakly emissive in aqueous environments. The prepared hydrogels exhibit the following features: I) color-tunable RTP emissions with ultra-long lifetimes up to 451.1 ms, II) excellent anti-swelling properties and stable persistent RTP emission even after being immersed in deionized water for months, III) efficient and large-scale preparation of hydrogel fibers by wet spinning technique. Experiment results and theoretical calculations show that the stable and long-lifetime RTP emissions of the hydrogels originate from the introduction of more nonconventional chromophores which are strongly crosslinked with ionic bonding between carboxylate groups and calcium ions and enhanced through-space interactions between them. This work provides a reliable strategy for designing nonaromatic hydrogels with stable and persistent RTP.