Two-Dimensional Titanium Nitride (Ti 2 N) MXene: Synthesis, Characterization, and Potential Application as Surface-Enhanced Raman Scattering Substrate.

We report on the synthesis, characterization, and application of Ti2 N (MXene), a two-dimensional transition metal nitride of M2 X type. Synthesis of nitride-based MXenes (Mn+1 Nn ) is difficult due to their higher formation energy from Mn+1 ANn and poor stability of Mn+1 Nn layers in the etchant employed, typically HF. Herein, the selective etching of Al from ternary layered transition metal nitride Ti2 AlN (MAX) and intercalation were achieved by immersing the powder in a mixture of potassium fluoride and hydrochloric acid. The multilayered Ti2 NTx (T is the surface termination) obtained was sonicated in DMSO and centrifuged to obtain few-layered Ti2 NTx . MXene formation was verified, and the material was completely characterized by Raman spectroscopy, XRD, XPS, FESEM-EDS, TEM, STM, and AFM techniques. Surface-enhanced Raman scattering (SERS) activity of the synthesized Ti2 NTx was investigated by fabricating paper, silicon, and glass-based SERS substrates. A Raman enhancement factor of 1012 was demonstrated using rhodamine 6G as the model compound with 532 nm excitation wavelength. Detection of trace level explosives with a simple paper-based SERS substrate with Ti2 N (MXene) as active material was also illustrated.