Engineering Multifunctionalized Silica Nanoparticles for Tailored Alginate‐Based Nanocomposite Hydrogels with Luminescence and Sensing Capabilities

Alginate-based nanocomposite hydrogels have exhibited diverse structures and properties depending on the material design; however, the potential of multifunctionalized nanomaterials for their fabrication remains unexplored. In this study, silica (SiO₂) nanoparticles are functionalized with three ligands (i.e., salicylaldehyde (SA), thenoyltrifluoroacetone (TTA), and N,N'-bis(carboxymethyl)-L-lysine (NTA)) to create a mixed functional surface. SA enables the incorporation of europium (Eu³⁺) ions onto the nanoparticle surface, while TTA and NTA further coordinate with Eu³⁺ ions to enhance luminescence and introduce amine functionality, respectively. Six types of lanthanide-containing SiO₂ nanoparticles are synthesized based on the capping ligands and subsequently integrated into a hydrazone-crosslinked network of alginate dialdehyde (ADA) and alginate modified with adipic dihydrazide (AADH). These nanocomposite hydrogels are systematically investigated for their luminescence, microstructures, mechanical properties, stability, and sensing capabilities. Notably, these luminescent nanocomposite hydrogels can differentiate aniline vapor from volatile amine vapors through linear discriminant analysis, with a detection limit of 88 ppb. This study highlights the fabrication of multifunctionalized SiO₂ nanoparticles as an effective engineering strategy for tailoring the characteristics and sensing abilities of alginate-based nanocomposite hydrogels, paving the way for the development of versatile hydrogels with expanded practical applications.