High-performance surface-enhanced Raman scattering substrate prepared by self-assembling of silver nanoparticles into the nanogaps of silver nanoislands

We report an effective and simple method to further enhance the surface-enhanced Raman scattering (SERS) by silver (Ag) nanoparticles (AgNPs) self-assembling into the nanogaps of an Ag nanoisland (AgNIs). The AgNIs prepared by dewetting of Ag film created a nanorough surface, which induced the Ag nanoparticles to regularly deposit into the nanogaps. AgNPs and AgNIs samples were also prepared for comparative analysis. Their SERS activities were investigated theoretically and experimentally. Experimental enhancement factors (EFs) for AgNPs, AgNIs, and AgNPs decorated AgNIs substrate (AgNPs-AgNIs) were ∼107, ∼106, ∼108, respectively, with relative standard deviation (RSD) of 66.1%, 12.9%, and 13.2%. Remarkable enhancement (EF≈108) and excellent reproducibility (RSD=13.2%) indicated the AgNPs-AgNIs had a high potential in practical application. Electromagnetic simulation using COMSOL Multiphysics demonstrated that the additional enhancement of the SERS effect could be mainly attributed to the improvement of the local electromagnetic field. Moreover, the deposition process of Ag nanoparticles was analyzed in detail to understand the reproducibility of AgNPs-AgNIs.