Ambient-stable MXene with superior performance suitable for widespread applications

MXenes, as attractive two-dimensional materials, have shown extraordinary potential for applications, however, their instability severely limits further research and applications on a large-scale and industrial level. Here, we overcome the environmental instability of MXene-Ti3C2Tx by an optimized synthetic route, including the synthesis of high-quality MAX phase (Ti3AlC2) and the post-treatment of Ti3C2Tx. The optimized Ti3C2Tx (O-Ti3C2Tx) achieves a dramatic improvement in stability. Even at low concentrations (∼0.1 mg/mL), the dark green aqueous dispersion of monolayer O-Ti3C2Tx showed no oxidation and degradation when aged under ambient conditions for two months, while conventional Ti3C2Tx required only ∼ 10 days for complete oxidative degradation under the same conditions. More importantly, compared with the conventional Ti3C2Tx, O-Ti3C2Tx exhibits higher conductivity, better nonlinear optical properties, excellent thermal stability, and comparable biocompatibility. In the application of pulsed laser with MXene as a saturable absorber, the conventional Ti3C2Tx leads to severe degradation of Q-switching performance due to its instability, while O-Ti3C2Tx shows excellent Q-switching performance in long-term operation. This work achieves a substantial solution to the instability problem of MXene-Ti3C2Tx without compromising its excellent performance, paving the way for the development of its practical applications.