A 3D Porous MXene/PNIPAAm Hydrogel Composite with Advanced Degradation Stability and Control of Electronic Properties in Air

This study reports the fundamental investigation of a composite material consisting of MXene (Ti₃C₂T_x) and a stimulus-responsive hydrogel (Poly(N-isopropylacrylamide)-PNIPAAm). Thereby, the fabrication and comparison of pure MXene and composite samples featuring either a compact or a highly porous 3D microstructure, reveal unique properties with respect to: i) controllable 3D spatial arrangement of MXene instead of the prevalent stacked-sheet structure, ii) reduction of oxidation-induced degradation of MXene and substantially enhanced stability over the course of three months for the composite, and iii) tunable electronic states in response to gas interactions. Material characterization is conducted by scanning electron microscopy and rheology to assess the microstructural and mechanical properties, and in a chemiresistive measurement setup for the determination of electrical properties and the evaluation of the composite's potential for VOC sensing in a gaseous environment with the test analyte acetone. These investigations reveal material effects and properties that address some of the key MXene-related challenges. Additionally, the interplay between the MXene and the hydrogel enables unprecedented opportunities for enhancing the sensing potential of stimulus-responsive hydrogels, specifically in gaseous environments.