Advancements in Ti₃C₂T_<i>x</i> MXene Stability: Synergistic Antioxidant Strategies and Their Impact on Long-Lasting Flexible Sensors

Abstract

Two-dimensional (2D) transition metal carbides (Ti₃C₂T_<i>x</i> MXene) have demonstrated substantial application potential across various fields, owing to their excellent metallic conductivity and solution processability. However, the rapid oxidation of Ti₃C₂T_<i>x</i> in aqueous environments, leading to a loss of stability within mere days, poses a significant obstacle for its practical applications. Herein, we introduce an antioxidant strategy that combines free radical scavenging with surface passivation, culminating in the design and synthesis of imidazolium-based ionic liquids (ILs) incorporating siloxane groups. By deploying a straightforward hydrolysis-addition reaction, we successfully fabricated IL-modified Ti₃C₂T_<i>x</i> materials (Ti₃C₂T_<i>x</i>-IL). The Ti₃C₂T_<i>x</i> -IL not only displayed exceptional conductivity exceeding 3.85 × 10⁴ S/m and hydrophilic contact angles below 45° but also showcased its superior chemical stability and antioxidation mechanisms through various analyses, including visual color change experiments, spectroscopic and energy spectrum characterization, free radical scavenging tests, and density-functional-theory-based molecular simulations. Furthermore, when utilized as a conductive filler in the fabrication of a poly(vinyl alcohol)/nanocellulose fiber (PVA/CNF) composite hydrogel (PCMIL), the resultant sensors exhibited remarkable mechanical performance with up to 535% strain, 1.59 MPa strength, 4.35 MJ/m³ toughness, and a conductivity of 3.40 mS/cm, as well as a high sensitivity gauge factor of 3.3. Importantly, even after 45 days of storage, the PCMIL retained most of its functionalities, demonstrating superior performance in human-machine interaction applications compared to hydrogels made from unmodified Ti₃C₂T_<i>x</i>. This research establishes a robust antioxidant protection strategy for Ti₃C₂T_<i>x</i>, offering substantial technical reinforcement for its prospective applications in the realm of flexible electronics and sensing technologies.