Engineered three-dimensional Au@Ag NCs/MXene/polystyrene microsphere SERS substrate for ultrasensitive detection

Surface-Enhanced Raman Scattering (SERS), with the exceptional single-molecule detection capability and high sensitivity, has become an advanced spectroscopic analysis method in fields such as chemical analysis and biosensing. Three-dimensional (3D) sandwich substrates, due to their unique structural characteristics, have attracted considerable attention for their ability to enhance SERS detection sensitivity. However, the controlled assembly of 3D sandwich substrates with bimetallic nanoparticles remains a challenge. In this paper, a fabrication method for constructing 3D sandwich substrates via a bottom-up approach is proposed. Using a liquid–liquid phase self-assembly method, Au@Ag nanocubes (Au@Ag NCs) were assembled on a polystyrene (PS) microsphere array with monolayer MXene (Ti 3 C 2 T X ) adsorption, successfully constructed an Au@Ag NCs/MXene/PS microsphere substrate. Furthermore, the SERS sensitivity of the substrate was evaluated using Rhodamine 6G (R6G), Crystal Violet (CV), and Aspartame (APM) molecules, and experimental results show that the detection limits are 10 −12 M, 10 −11 M, and 0.0313 g/L (1.06 × 10 −4 M), respectively, with excellent uniformity and stability of the substrate. These findings demonstrate that the constructed 3D substrate exhibits outstanding SERS performance and holds significant potential for applications in environmental pollutant detection and food safety.