Photo-switchable nanoripples in Ti3C2Tx MXene

TL;DR

This paper demonstrates that femtosecond laser pulses can induce reversible, photo-switchable nanoripples in Ti3C2Tx MXene, creating a dynamic, anisotropic nanostructure with potential applications in optics and sensing.

Contribution

It reveals the ultrafast structural dynamics of Ti3C2Tx MXene and introduces a method to reversibly switch its surface morphology using light.

Findings

Fast electron-phonon coupling time of 230 femtoseconds.

Reversible transformation into nanorippled metamaterial.

Potential for light-controlled optical and electronic properties.

Abstract

MXenes are two-dimensional materials with a rich set of remarkable chemical and electromagnetic properties, the latter including saturable absorption and intense surface plasmon resonances. To fully harness the functionality of MXenes for applications in optics, electronics and sensing, it is important to understand the interaction of light with MXenes on atomic and femtosecond dimensions. Here, we use ultrafast electron diffraction and high-resolution electron microscopy to investigate the laser-induced structural dynamics of Ti3C2Tx nanosheets. We find an exceptionally fast lattice response with an electron-phonon coupling time of 230 femtoseconds. Repetitive femtosecond laser excitation transforms Ti3C2Tx through a structural transition into a metamaterial with deeply sub-wavelength nanoripples that are aligned with the laser polarization. By a further laser illumination, the material is reversibly photo-switchable between a flat and rippled morphology. The resulting nanostructured MXene metamaterial with directional nanoripples is expected to exhibit an anisotropic optical and electronic response as well as an enhanced chemical activity that can be switched on and off by light.