Morphology-engineered Au–Ag nanoshuttle superlattice membranes for ultrasensitive and uniform SERS detection

Abstract Plasmonic superlattices of anisotropic noble metal nanoparticles offer precise control over light–matter interactions, enabling ultrasensitive surface-enhanced Raman scattering (SERS) detection. By fine-tuning the morphology, composition and interparticle coupling of nanoparticle building blocks, the optical enhancement properties of two-dimensional nanoarchitectures can be precisely engineered for superior sensing performance. Here, we report the programmable synthesis of bimetallic gold‒silver nanoshuttles (Au–Ag NSs) with controllable aspect ratios, namely ultra-short (US), long (L) and ultra-long (UL), via an optimized seed-mediated growth approach. By rationally controlling the polystyrene ligand capping and evaporation conditions at the gas–liquid interface, these Au–Ag NSs were self-assembled into free-standing, single-layer superlattice membranes exhibiting highly ordered two-dimensional packing with uniform interparticle spacing. Using 4-aminothiophenol as a molecular probe, the US-NS membranes delivered outstanding SERS performance, achieving a detection limit of 0.1 nM and an enhancement factor of approximately 105. Moreover, they exhibited remarkable signal uniformity across large areas, attributed to the well-distributed electromagnetic field hotspots within the ordered superlattice. This study establishes a robust strategy for constructing high-performance plasmonic architectures, offering substantial promise for ultrasensitive trace chemical detections.