Ti₃AlC₂ MAX and Ti₃C₂ MXene Quantum Sheets for Record-High Optical Nonlinearity

Area of Science:

• Materials Science
• Nanotechnology
• Optoelectronics

Background:

• Two-dimensional (2D) transition-metal carbides (MXenes) are noted for unique properties.
• Transforming MXenes into sub-5-nm quantum sheets (QSs) is a critical but underexplored area.
• Existing methods for MXene processing are limited.

Purpose of the Study:

• To demonstrate the synthesis of monolayer, sub-5-nm lateral sized Ti3AlC2 MAX and Ti3C2 MXene QSs.
• To investigate the photoluminescence and nonlinear optical properties of these novel MXene QSs.
• To explore the potential of MXene QSs in nonlinear optics.

Main Methods:

• An all-physical top-down method was employed for MXene QS synthesis.
• Characterization of QS morphology and size.
• Measurement of photoluminescence and nonlinear saturation absorption (NSA) in QS dispersions and hybrid films.

Main Results:

• Achieved exceptionally high yields (>15 wt %) of monolayer Ti3AlC2 MAX and Ti3C2 MXene QSs with sub-5-nm lateral sizes.
• Observed unique photoluminescence from QS dispersions.
• Demonstrated remarkable nonlinear saturation absorption (NSA) in QSs-poly(methyl methacrylate) (PMMA) hybrid thin films, with modulation depths up to 49.9% and saturation intensities as low as 1.16 MW cm⁻².

Conclusions:

• Successfully synthesized sub-5-nm MXene QSs using a scalable, physical method.
• The synthesized MXene QSs exhibit promising photoluminescent and nonlinear optical properties.
• These findings suggest significant potential for MAX/MXene QSs in nonlinear optics and related fields.