Layer-by-layer thin films of Ti₃C₂ MXene and gold nanoparticles as an ideal SERS platform

The combination of plasmonic metals and MXene, as a new and interesting member of the 2D material class, may provide unique advantages in terms of low cost, versatility, flexibility, and improved activity as an ideal surface-enhanced Raman spectroscopy (SERS) platform. Despite the recent progress, the present studies on the utilization of plasmonic metal/MXene-based SERS systems are quite limited and thereby benefits of the extraordinary properties of this combination cannot be realized. In this study, for the first time, we propose layer-by-layer (LbL) thin films of Ti₃C₂ MXene and gold nanoparticles (AuNPs) as a robust SERS platform (Ti₃C₂/AuNPs). For this, Ti₃C₂ MXene was synthesized from the Ti₃AlC₂ MAX phase, and the Ti₃C₂/AuNP LbL film was fabricated <i>via</i> a vacuum-assisted filtration method to create consecutive layers of each material. This procedure produced densely distributed AuNPs in the LbL film in a well-controlled manner. The SERS activity tests for methylene blue and DTNB as Raman reporter molecules showed that they exhibited enhancement factors of 1.5 × 10⁶ and 1.2 × 10⁶ and limits of detection of 1 × 10^-8 M, and 2.5 × 10^-8 M, respectively. Various mechanisms, including the formation of hotspots due to AuNPs on the interlayer of Ti₃C₂, improved surface roughness and resultant optical activity, as well as the synergistic effect between Ti₃C₂ and AuNPs, contributed to the resultant SERS activity to some extent. This study has proven the feasibility of the Ti₃C₂/AuNP LbL system as a robust SERS-based sensor platform, paving the way for its use in various biological and chemical applications.