Switching the Nonlinear Optical Absorption of Titanium Carbide MXene by Modulation of the Surface Terminations

Hui Li; Saiyi Chen; Danil W Boukhvalov; Zhiyang Yu; Mark G Humphrey; Zhipeng Huang; Chi Zhang

doi:10.1021/acsnano.1c07060

Switching the Nonlinear Optical Absorption of Titanium Carbide MXene by Modulation of the Surface Terminations

ACS Nano. 2022 Jan 25;16(1):394-404. doi: 10.1021/acsnano.1c07060. Epub 2022 Jan 13.

Authors

Hui Li¹, Saiyi Chen¹, Danil W Boukhvalov^{2

3}, Zhiyang Yu⁴, Mark G Humphrey⁵, Zhipeng Huang¹, Chi Zhang¹

Affiliations

¹ School of Chemical Science and Engineering, Tongji University, Shanghai, 200092, P. R. China.
² Jiangsu Co-Innovation Center of Efficient Processing and Utilization of Forest Resources, College of Science, Nanjing Forestry University, Nanjing, 210037, P. R. China.
³ Institute of Physics and Technology, Ural Federal University, Mira Street 19, Yekaterinburg, 620002, Russia.
⁴ State Key Laboratory of Photocatalysis on Energy and Environment, College of Chemistry, Fuzhou University, Fuzhou, 350002, P. R. China.
⁵ Research School of Chemistry, Australian National University, Canberra, Australian Capital Territory 2601, Australia.

PMID: 35023722
DOI: 10.1021/acsnano.1c07060

Abstract

Surface terminations of two-dimensional materials should have a strong influence on the nonlinear optical (NLO) properties, but the relationship between surface terminations and NLO properties has not yet been reported. In this work, switching the NLO properties of MXenes (Ti₃C₂T_x) via "surface terminations modulation" is explored. The surface terminations of Ti₃C₂T_x are modulated by electrochemical treatment, resulting in different states (viz., Ti₃C₂T_x(pristine), Ti₃C₂T_x(═O rich), and Ti₃C₂T_x(-OH rich)). The sign and magnitude of the effective NLO absorption coefficient (β_eff) change with the surface terminations. Ti₃C₂T_x(═O rich) shows a relatively large saturable absorption (SA) with laser excitation at 515 nm (β_eff = -1020 ± 136.2 cm GW^-1), while reverse saturable absorption (RSA) is found in Ti₃C₂T_x(pristine) and Ti₃C₂T_x(-OH rich). The RSA of Ti₃C₂T_x(pristine) and Ti₃C₂T_x(-OH rich) is attributed to excited-state absorption, while the SA of Ti₃C₂T_x(═O rich) is associated with Pauli blocking. With laser excitation at 800 nm, the β_eff of Ti₃C₂T_x(-OH rich) is 113 ± 3.2 cm GW^-1, 1.68 times that of Ti₃C₂T_x(pristine); the RSA is caused by photon-induced absorption. Our results reveal a correlation between surface terminations and NLO properties, highlighting the potential of MXenes in photoelectronics.

Keywords: MXenes; density of states; electrochemistry; nonlinear optical absorption; reverse saturable absorption; saturable absorption; surface terminations.