Theoretical and Experimental Studies of Ti₃C₂ MXene for Surface-Enhanced Raman Spectroscopy-Based Sensing

Recent advances in MXenes with high carrier mobility show great application prospects in the surface-enhanced Raman scattering (SERS) field. However, challenges remain regarding the improvement of the SERS sensitivity. Herein, an effective strategy considering charge-transfer resonance for semiconductor-based substrates is presented to optimize the SERS sensitivity with the guidance of the density functional theory calculation. The theoretical calculation predicted that the excellent SERS enhancement for methylene blue (MeB) on Ti₃C₂ MXene can be excited by both 633 and 785 nm lasers, and the Raman enhanced effect is mainly originated from the charge-transfer resonance enhancement. In this work, the Ti₃C₂ MXenes exhibit an excellent SERS sensitivity with an enhancement factor of 2.9 × 10⁶ and a low detection limit of 10^-7 M for MeB molecules. Furthermore, the SERS enhancement of Ti₃C₂ and Au-Ti₃C₂ substrates exhibit higher selectivity on different molecules, which contributes to the detection of target molecules in complex solution environments. This work can provide some theoretical and experimental basis for the research on SERS activity of other MXene materials.