Two-Dimensional\nTitanium Nitride (Ti<sub>2</sub>N)\nMXene: Synthesis, Characterization, and Potential Application as Surface-Enhanced\nRaman Scattering Substrate

We\nreport on the synthesis, characterization, and application of\nTi₂N (MXene), a two-dimensional transition metal nitride\nof M₂X type. Synthesis of nitride-based MXenes (M_<i>n</i>+1N_<i>n</i>) is difficult due\nto their higher formation energy from M_<i>n</i>+1AN_<i>n</i> and poor stability of M_<i>n</i>+1N_<i>n</i> layers in the etchant\nemployed, typically HF. Herein, the selective etching of Al from ternary\nlayered transition metal nitride Ti₂AlN (MAX) and intercalation\nwere achieved by immersing the powder in a mixture of potassium fluoride\nand hydrochloric acid. The multilayered Ti₂NT_<i>x</i> (T is the surface termination) obtained was sonicated\nin DMSO and centrifuged to obtain few-layered Ti₂NT_<i>x</i>. MXene formation was verified, and the material\nwas completely characterized by Raman spectroscopy, XRD, XPS, FESEM-EDS,\nTEM, STM, and AFM techniques. Surface-enhanced Raman scattering (SERS)\nactivity of the synthesized Ti₂NT_<i>x</i> was investigated by fabricating paper, silicon, and glass-based\nSERS substrates. A Raman enhancement factor of 10¹² was\ndemonstrated using rhodamine 6G as the model compound with 532 nm\nexcitation wavelength. Detection of trace level explosives with a\nsimple paper-based SERS substrate with Ti₂N (MXene) as\nactive material was also illustrated.