Large-area Ag “sesame cake-like” arrays with high-density hotspots for efficient SERS analysis

[Display omitted] •A large-area Ag “sesame cake-like” (ASCL) array can be facilely fabricated on a rigid substrate and a flexible substrate.•The ASCL array shows excellent polarization independence for SERS performance.•The ASCL array substrate exhibits great SERS performance for detecting the chemical residues.•The flexible ASCL array substrate possesses noticeable stability and flexibility. Nanogap-rich plasmonic metal nanostructures have attracted great attention in surface enhanced Raman scattering (SERS) applications due to their prominent performances. Herein, utilizing enhanced surface diffusion of Ag atoms on a low energy surface, a facile fabrication strategy is developed to construct a large-area Ag “sesame cake-like” (ASCL) array by combining the ultra-thin alumina mask (UTAM) and vapor deposition technique. Owing to the multiple plasmonic coupling effects, the proposed ASCL array possesses enormous hotspots responsible for remarkable sensitivity with an enhancement factor of 4.9 × 106, excellent reproducibility with a relative standard deviation (RSD) smaller than 7.12 % and obvious polarization independent in SERS analysis, which are confirmed by numerical simulations. In addition, the possibility to be fabricated on the flexible substrate makes the ASCL array substrate well meet the increasing demands for practical applications in the fields of food safety, health and environment monitoring.