Ultrastable partially etched Ti3AlC2 with tunable nonlinear scattering and absorption properties

Two-dimensional MXene materials have demonstrated significant potential in the field of nonlinear optics. However, their environmental stability remains a challenge, limiting their practical applications. In this study, a fluoride-free etching strategy is proposed for the synthesis of ultrastable partially etched Ti3AlC2. A tunable transition from nonlinear scattering (NLS) to saturable absorption (SA) is achieved via ultrasonic-assisted particle size regulation. This transformation is attributed to the enhanced heat dissipation capacity of the samples resulting from the increase in the specific surface area. Z-scan measurements reveal that the sample (S-Ti3Al1−xC2) obtained after 60 minutes of ultrasonication exhibits pronounced saturable absorption under 532 nm laser excitation, with a nonlinear absorption coefficient of −2.4844 cm GW−1 and a modulation depth of 29.57%, comparable to that of fully etched Ti3C2Tx. In addition, the presence of residual aluminum atoms endows the material with excellent oxidation resistance. After undergoing a high-temperature aging process at 80 °C for 30 hours, S-Ti3Al1−xC2 retained over 85% of their initial saturable absorption properties. Furthermore, no TiO2 peaks were observed in the XRD pattern, indicating minimal oxidation. These findings demonstrate a safe and effective preparation method for the synthesis of highly stable nonlinear optical materials.