Injectable and Self‐Healable Luminescent Europium‐Containing Gelatin/Polydextran/Laponite Nanocomposite Hydrogels for Distinguishing Formaldehyde in Volatile Organic Compounds

Detecting volatile organic compounds (VOCs) is essential for human health and environmental safety. In this study, luminescent lanthanide-based nanocomposite hydrogels featuring injectable and self-healing properties are developed for VOC sensing. Europium-containing laponite (Eu³⁺@Lap) and 2-thiophenyltrifluoroacetone (TTA)-modified Eu³⁺@Lap (Eu³⁺(TTA)@Lap) are incorporated into a dynamic cross-linked hydrogel network composed of polyethyleneimine-modified gelatin and polydextran aldehyde (PG/PDA), resulting in PG/PDA/Eu³⁺@Lap and PG/PDA/Eu³⁺(TTA)@Lap hydrogels, respectively. The luminescent properties, microstructures, and mechanical characteristics of these two nanocomposite hydrogels are systematically investigated. The interactions of VOCs with the laponite luminophores alter the luminescence of the gels and produce unique response patterns for each VOC. PG/PDA/Eu³⁺(TTA)@Lap lyophilized hydrogel presented a superior sensing capability compared to PG/PDA/Eu³⁺@Lap lyophilized hydrogel in distinguishing formaldehyde from various VOCs, with the calculated detection limit of 39 ppb. This work highlights the importance of the effective antenna effect between organic ligands and lanthanide ions in improving the sensing capability of the luminescent nanocomposite hydrogels and demonstrates the promise of the dynamic cross-linked PG/PDA/Eu³⁺(TTA)@Lap hydrogel as an innovative platform in environmental VOC monitoring.