Guzelturk Burak, Kamysbayev Vladislav, Wang Di, Hu Huicheng, Li Ruiyu, King Sarah B, Reid Alexander H, Lin Ming-Fu, Wang Xijie, Walko Donald A, Zhang Xiaoyi, Lindenberg Aaron, Talapin Dmitri V
X-ray Science Division, Argonne National Laboratory, Lemont, Illinois 60439, United States.
Department of Chemistry, James Franck Institute, and Pritzker School of Molecular Engineering, University of Chicago, Chicago, Illinois 60637, United States.
Nano Lett. 2023 Apr 12;23(7):2677-2686. doi: 10.1021/acs.nanolett.2c05001. Epub 2023 Mar 14.
MXenes have the potential for efficient light-to-heat conversion in photothermal applications. To effectively utilize MXenes in such applications, it is important to understand the underlying nonequilibrium processes, including electron-phonon and phonon-phonon couplings. Here, we use transient electron and X-ray diffraction to investigate the heating and cooling of photoexcited MXenes at femtosecond to nanosecond time scales. Our results show extremely strong electron-phonon coupling in TiC-based MXenes, resulting in lattice heating within a few hundred femtoseconds. We also systematically study heat dissipation in MXenes with varying film thicknesses, chemical surface terminations, flake sizes, and annealing conditions. We find that the thermal boundary conductance (TBC) governs the thermal relaxation in films thinner than the optical penetration depth. We achieve a 2-fold enhancement of the TBC, reaching 20 MW m K, by controlling the flake size or chemical surface termination, which is promising for engineering heat dissipation in photothermal and thermoelectric applications of the MXenes.
MXenes在光热应用中具有高效光热转换的潜力。为了在这类应用中有效利用MXenes，了解其潜在的非平衡过程很重要，这些过程包括电子 - 声子以及声子 - 声子耦合。在此，我们使用瞬态电子和X射线衍射来研究飞秒到纳秒时间尺度下光激发MXenes的加热和冷却过程。我们的结果表明，基于TiC的MXenes中存在极强的电子 - 声子耦合，导致在几百飞秒内晶格加热。我们还系统地研究了不同薄膜厚度、化学表面终止、薄片尺寸和退火条件下MXenes中的热耗散。我们发现，热边界电导（TBC）控制着比光穿透深度更薄的薄膜中的热弛豫。通过控制薄片尺寸或化学表面终止，我们实现了TBC提高2倍，达到20 MW m⁻² K⁻¹，这对于在MXenes的光热和热电应用中设计热耗散很有前景。
