Fabrication of sandwich nanostructured substrates with Au@Ag NCs/Graphene/AgMP for ultrasensitive SERS detection

This paper presents the design of a bottom-up "sandwich" configuration substrate via electrostatic self-assembly. A silver microplate (AgMP) serves as the stable structural base, onto which monolayer graphene is wet-transferred. Au@Ag nanocubes (Au@Ag NCs) are then assembled on the upper layer through liquid-liquid three-phase self-assembly, forming a Au@AgNCs/G/AgMP “sandwich” substrate. The combination of electromagnetic enhancement from noble metal nanoparticles and chemical enhancement from graphene synergistically amplifies the signal of detected molecules, leading to significant Surface-Enhanced Raman Scattering (SERS) enhancement. Experimental results demonstrate that this substrate can detect Rhodamine 6 G (R6G) at concentrations as low as 10 –12 M and Crystal Violet (CV) at 10 –9 M. Moreover, the substrate can detect Aspartame (APM) at concentrations as low as 0.0625 g/L, well below the typical daily intake levels for humans. These findings indicate that the substrate exhibits excellent SERS performance and holds significant potential for broad applications.