Lanthanide coordinated multicolor luminescent polymeric hydrogels

Multicolor luminescent polymeric hydrogels (LPHs) have advanced significantly in recent years by leveraging their unique wet and soft properties that mimic those of biological skin. Their stimuli-responsive characteristics and tunable luminescence have facilitated significant advancements in responsive sensing, anti-counterfeiting technologies, and biomimetic actuators. The luminescent groups of LPHs primarily include organic fluorophores, fluorescent proteins, lanthanide complexes, and luminescent nanoparticles. Notably, lanthanide ion coordination luminescence is distinguished by high quantum efficiency, narrow emission bands, superior color purity, and photostability, thereby positioning it as a crucial component in multicolor LPHs. However, the low absorption coefficients of lanthanide ions in the visible and ultraviolet regions restrict their intrinsic luminescence. Coordinating these ions with organic compounds that have high absorption coefficients facilitates energy transfer, thereby enhancing the emission of the lanthanide ions. This review systematically classifies lanthanide-coordinated multicolor LPHs according to synthesis strategies, including physically mixed, chemically covalently grafted, and self-assembled supramolecular LPHs. Finally, this review addresses the current challenges and future prospects in this field, aiming to garner increased interest from interdisciplinary researchers.