Effect of Etching Condition on Vibrational Characteristics of Two Dimensional MXenes

Two-dimensional materials based on transition metal carbides and nitrides called MXenes have been intensively studied due to their unique properties including metallic conductivity, hydrophilicity, and structural diversity and have shown great potential in several applications, for example, energy storage, sensing, and optoelectronics. In this work, we synthesized different batches of Ti₃C₂T_X MXenes by tuning temperature and time. The first batch of MXene was synthesized by adding Ti₃AlC₂ powders into the LiF/HCl solution and was etched for 7 days at room temperature whereas the second batch was etched for seven days at 70 °C. We observed several Raman bands including narrow peaks centered around 400 and 600 cm⁻¹ and broad peaks ~ 1365 and 1580 cm⁻¹. The presence of these lower wavenumber bands indicates the formation of Ti₃C₂T_X whereas the broad peaks centered around 1350 and 1570 cm⁻¹ are related to D and G bands of graphitic carbon. The relative intensity of Ti-C vibrational peaks is different between batch 1 and batch 2 of Ti₃C₂T_X suggesting the change in surface structure. The different intensity of D and G bands between two batches indicates that the extent of amorphous carbon can also be tuned by etching. These observations are further supported by X-ray diffraction and scanning electron microscopy images.