Surface termination dependent optical characteristics of MXene nanoflakes

Two-dimensional (2D) transition metal carbides, nitrides, and carbonitrides, known as MXenes, are an expanding class of 2D materials. With the compositional diversity and range of surface terminations, they have the potential to facilitate the development of novel devices. Herein, based on quantum-mechanical simulations via time-dependent density functional theory, we investigate how the M element (Ti or V) and surface terminations (Tx such as F and O) affect the optical and plasmonic characteristics of M2CTx MXene nanoflakes. We reveal the formation of localized surface plasmon resonances (LSPRs) in MXene nanoflakes. Interestingly, the Janus MXene nanoflake Ti2CFO (top surface terminated with F and bottom surface terminated with O) produces the strongest and narrowest infrared LSPR, which is attributable to its largest out-of-plane time-dependent dipole moment. The findings of this study may be helpful to those exploring on MXene plasmonics.