Square-centimeter-scale 2D-arrays of Au@Ag core–shell nanoparticles towards practical SERS substrates with enhancement factor of 107

A series of two-dimensional (2D) arrays of Au-core/Ag-shell nanoparticles with fixed sub-3 nm gap distance was obtained on 1 cm2 substrates. All 2D arrays resulted in homogeneous and dense monolayers of nanoparticles thanks to our original hybrid deposition method based on self-assembly. Midnanosized gold nanoparticles were used as the core and Ag-shell with different thicknesses were grown to tune the LSPR to around 633 nm. The resulting SERS substrates enhanced Raman signal by up to about 107 with remarkable spatial uniformity. Our SERS substrate is highly promising as a practical SERS-based sensor substrate.