Fourier-Transform\nInfrared Spectral Library of MXenes

Fourier-transform infrared (FTIR) spectroscopy characterization\nis a powerful and easy-to-use technique frequently employed for the\ncharacterization and fingerprinting of materials. Although MXenes\nare a large and fastest growing family of inorganic 2D materials,\nthe lack of systematic FTIR spectroscopy studies hinders its application\nto MXenes and often leads to misinterpretation of the results. In\nthis study, we report experimental and calculated FTIR spectra of\n12 most typical carbide and carbonitride MXenes with different compositions\n(5 transition metals) and all four basic structures, including Ti<sub>2</sub>CT<sub><i>x</i></sub>, Nb<sub>2</sub>CT<sub><i>x</i></sub>, Mo<sub>2</sub>CT<sub><i>x</i></sub>,\nV<sub>2</sub>CT<sub><i>x</i></sub>, Ti<sub>3</sub>C<sub>2</sub>T<sub><i>x</i></sub>, Ti<sub>3</sub>CNT<sub><i>x</i></sub>, Mo<sub>2</sub>TiC<sub>2</sub>T<sub><i>x</i></sub>, Mo<sub>2</sub>Ti<sub>2</sub>C<sub>3</sub>T<sub><i>x</i></sub>, Nb<sub>4</sub>C<sub>3</sub>T<sub><i>x</i></sub>, V<sub>4</sub>C<sub>3</sub>T<sub><i>x</i></sub>, Ta<sub>4</sub>C<sub>3</sub>T<sub><i>x</i></sub>, and Mo<sub>4</sub>VC<sub>4</sub>T<sub><i>x</i></sub>. The measurements were\nperformed on delaminated MXene flakes incorporated in KBr pellets\nin the 4000–400 cm<sup>–1</sup> range. We provide detailed\ninstructions for sample preparation, data collection, and interpretation\nof FTIR spectra of MXenes. Background correction and spectra smoothing\nare applied to obtain clear FTIR peaks corresponding to bond vibrations\nin MXenes. Density functional theory calculations were used for the\nprecise assignment of all characteristic FTIR peaks and an in-depth\nanalysis of the vibration modes. This work aims to provide the 2D\nmaterial community with the FTIR spectroscopy technique as a reliable\nmethod for identifying and analyzing MXenes.