Au-Ag bimetallic trapezoidal nanoassembly substrate for surface-enhanced raman scattering enhancement

Surface-enhanced Raman scattering (SERS) utilizes the plasmonic resonance of nanostructures to dramatically amplify Raman signals through localized electromagnetic field enhancement, enabling sensitive detection across diverse fields. However, the widespread adoption of conventional noble-metal SERS substrates is hindered by challenges such as poor signal reproducibility, non-uniform distribution of electromagnetic 'hot spots,' and limited stability. Here, we present a highly ordered bimetallic Au-Ag trapezoidal assembly array fabricated via an asymmetrically wettable silicon micropillar template for a high-performance SERS substrate. The Au-Ag bimetallic structure within the assembled architecture facilitates strong interfacial plasmonic coupling, which, combined with the light-trapping effect of the trapezoidal nanowire geometry, generates intense and spatially uniform electromagnetic fields. The substrate demonstrates an exceptional average enhancement factor exceeding 10¹²using rhodamine 6 G as the probe molecule, surpassing the performance of its single-metal counterparts and exhibiting excellent signal reproducibility with a relative standard deviation of less than 5%. This study provides a novel assembly strategy for binary metal nanoparticles, offering a new perspective for the fabrication of high-performance and highly sensitive SERS substrates.