Straightforward Assessment of Structural Disorder in Ti3C2T x MXene Using Raman Spectroscopy: Implications for Defect Engineering

Abstract

MXenes, a large family of two-dimensional transition-metal carbides and nitrides, have attracted considerable interest owing to their unique physicochemical properties. Structural defects play a key role in tuning these properties, yet their characterization remains highly challenging. Herein, controlled Ne2+ ion implantation of Ti3AlC2 MAX phases is employed to generate well-defined defect densities, followed by exfoliation through a mild LiF/HCl route to obtain defect-engineered Ti3C2Tx MXenes. Raman spectroscopy reveals a high sensitivity of A1g vibration at 206 cm–1 to structural disorder in the Ti3C2Tx MXene skeleton. In particular, the full width at half-maximum (FWHM) of this mode increases linearly with implantation fluence, providing a direct semiquantitative descriptor of structural disorder. The relevance of the A1g mode as a disorder marker is further confirmed using a second defect-generation route based on increasingly harsh HF etching conditions. Finally, the Raman results are corroborated by complementary XPS/HAXPES and TEM-EELS analyses, which reveal defect-induced modifications of the MXene structure while preserving its overall crystallographic framework. Together, these findings establish Raman spectroscopy as a straightforward, nondestructive, and widely accessible tool for the assessment of structural disorder in Ti3C2Tx MXenes, with strong relevance for the development of defect engineering strategies in this large class of 2D materials.