MXene (Ti₃C₂T_x)-Ag nanocomplex as efficient and quantitative SERS biosensor platform by in-situ PDDA electrostatic self-assembly synthesis strategy

Recent years, two-dimensional transition metal carbonitrides, MXene, have emerged as SERS substrates due to their unique optical and electrical properties. In order to combine the advantages of metal nanoparticles and MXene for SERS substrates, this paper prepared an MXene (Ti₃C₂T_x) -Ag nanoparticles (NPs) hybrid biosensor through in-situ electrostatic self-assembly method, in which the citrate-coated Ag NPs are loaded on the negatively surface of Ti₃C₂T_x flakes through positively charged PDDA polymer. The characterizations show that a large number of Ag NPs uniformly adsorb on both side of Ti₃C₂T_x nanosheets. The prepared platform exhibits excellent SERS performance, long-term stability and good uniformity by detecting 4-MBA molecules. The electromagnetic field distribution was simulated to theoretically show the Raman enhancement mechanism of this platform. In order to explore the possible application of the sensor in clinical diagnosis and monitoring of biological environment, the platform was used for biomolecule detection. The detection limit of adenine molecules can be as low as 10⁻⁸ M. For dopamine molecules with concentration ranging from 5 × 10^-6 M to 5 × 10⁻⁸ M, the SERS results show a linear relationship between peak intensity and concentration of dopamine molecules. The biosensor was applied for serum detection. The results suggest that MXene-PDDA-Ag NPs hybrid platform could be used as a sensitive and uniform biosensor for label-free quantitative detection of bio-molecular based on SERS method, which could be applied in the field of biotechnology.