Modulation of biaxial strains on the optical responses of defective Ti3C2 Tx (T = F, O, OH) MXenes

MXenes have potential applications for adsorbing radioactive elements and protecting surfaces of radioactive materials. Keeping integrity is important for practical applications. Thus, an efficient way for detecting hole defects as well as strain conditions becomes required. Here based on first-principles calculations on the electronic structures and optical properties, we present a systematic result for optical detections on hole defects as well as strain conditions of Ti₃C₂T₂ (T = F, O, OH) MXenes. Introduction of hole defects affects the chemical bondings of surrounding functional groups, and biaxial strains from −4 % to 4 % causes negligible bonding distortions. The change in bonding lengths under different strains is below 0.05 Å. Since the electronic states of functional groups distribute deeply away from the Fermi level, the absorption spectra in the ultraviolet frequency range show obvious modulation effects for hole defects and strain conditions. A quantitative relationship has been established. Our results can be used for detecting both the defect structures and strain conditions of Ti₃C₂T₂ (T = F, O, OH) MXenes.