Tuning the electromagnetic field coupling between nanoporous silver and silver nanoparticles connected by hybridized oligonucleotide

► A nanoporous Ag/DNA-Cy5/Ag nanoparticle sandwich as SERS substrate was constructed. ► dsDNA was used to control the distance between Ag nanoparticle and nanoporous Ag. ► A hot spot was formed in the region between closely-spaced nanostructures. ► The SERS signal of Cy5 at the hot spot decreased with increasing the length of dsDNA.