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-Ti 3 C 2 T x by an optimized synthetic route, including the synthesis of high-quality MAX phase (Ti 3 AlC 2 ) and the post-treatment of Ti 3 C 2 T x . The optimized Ti 3 C 2 T x (O-Ti 3 C 2 T x ) achieves a dramatic improvement in stability. Even at low concentrations (∼0.1 mg/mL), the dark green aqueous dispersion of monolayer O-Ti 3 C 2 T x showed no oxidation and degradation when aged under ambient conditions for two months, while conventional Ti 3 C 2 T x required only ∼ 10 days for complete oxidative degradation under the same conditions. More importantly, compared with the conventional Ti 3 C 2 T x , O-Ti 3 C 2 T x 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 Ti 3 C 2 T x leads to severe degradation of Q-switching performance due to its instability, while O-Ti 3 C 2 T x shows excellent Q-switching performance in long-term operation. This work achieves a substantial solution to the instability problem of MXene-Ti 3 C 2 T x without compromising its excellent performance, paving the way for the development of its practical applications.