High-permittivity Solvents Increase MXene Stability and Stacking Order Enabling Ultraefficient Terahertz Shielding

Area of Science:

• Materials Science
• Nanotechnology
• Condensed Matter Physics

Background:

• Two-dimensional transition metal carbides and nitrides (MXenes) offer unique properties but face challenges with oxidation and instability in water-based processing.
• Conventional processing methods limit the practical applications of MXenes due to their inherent instability.

Purpose of the Study:

• To investigate high permittivity solvents for enhancing the stability and dispersibility of MXenes.
• To explore the relationship between solvent properties, MXene structural order, and Terahertz shielding effectiveness.

Main Methods:

• Experimental and theoretical investigations using high permittivity solvents like N-methylformamide (NMF) and formamide (FA).
• Fabrication of thin MXene films on carbon nanotube (CNT) substrates.
• Characterization of Terahertz (THz) shielding effectiveness (SE) using THz spectroscopy.
• Analysis of MXene stacking order and mesoscopic porosity via small-angle X-ray scattering (SAXS).

Main Results:

• High permittivity solvents (NMF, FA) significantly improve MXene stability and dispersibility compared to classical solvents.
• Thin MXene films (< 2 µm) on CNT substrates exhibit high THz shielding effectiveness (40-60 dB) over 0.3-1.6 THz.
• A high degree of MXene stacking order and controlled mesoscopic porosity are crucial for effective THz shielding.

Conclusions:

• Selecting high permittivity solvents is critical for overcoming MXene processing limitations.
• The findings provide a mechanistic understanding for stable MXene processing and effective THz shielding.
• This research guides generic MXene applications, particularly in telecommunications, and the broader processing of 2D materials.