Controlled assembly of sliver nanocap arrays with tunable gaps for molecular sensing using SERS

A convenient nanotechnique for fabrication of highly ordered hemispherical silver nanocap arrays templated by porous anodic alumina membranes as robust and cost-efficient surface-enhanced Raman scattering (SERS) substrates is reported. This geometry exhibits a high Raman signal due to periodically hexagonal arrangements and gap control between the nanostructures in the sub-10 nm regime. The surface structure can further be tuned to optimize the enhancement factor according to optional porous anodic alumina fabrication and silver deposition parameters.