Lanthanide Ionic Radius Modulation for Tailored Triple-Cross-Linked Luminescent Gelatin/Alginate Hydrogels:...

Lanthanide-containing hydrogels have emerged as a promising category of luminescent materials for sensing applications. However, a systematic investigation of lanthanide ions with varying ionic radii to reveal the structure-property-function relationships within the hydrogel network remains unexplored. This study integrates different lanthanide (Ln^{3 +}) ions (i.e., samarium (Sm^{3 +}), europium (Eu^{3 +}), or terbium (Tb^{3 +})) into polymeric networks composed of phenylboronic acid-grafted polyethylenimine (PBA-PEI)-modified gelatin (PPG) and alginate-dialdehyde (ADA), resulting in triple-cross-linked PPG/ADA-Ln^{3 +} hydrogels that are stabilized via dynamic bonds. The influence of lanthanide ionic radius on the microstructures, properties (i.e., luminescence, rheological behavior, mechanical strength, swelling capacity, and stability), and sensing performance is systematically investigated. PPG/ADA-Ln^{3 +} lyophilized hydrogels demonstrate a remarkable ability to differentiate acidic and basic vapors in volatile organic compounds through linear discriminant analysis (LDA), and this capability is further explored for bacterial differentiation. Overall, smaller Tb^{3 +} ions induce the formation of denser networks with enhanced mechanical properties and contribute superior sensing capabilities to the hydrogel, attributed to optimized coordination with the carboxylate groups of the polymers. This comprehensive study elucidates the critical role of lanthanide ionic radius in shaping the structural and functional attributes of PPG/ADA-Ln^{3 +} hydrogels, showing their potential as versatile biomaterials with tailored properties for a wide range of applications.