Hierarchical porous plasmonic metamaterials for reproducible ultrasensitive surface-enhanced raman spectroscopy

Surface-enhanced Raman spectroscopy (SERS) has emerged as one of the most versatile tools for sensing and imaging chemical and biological analytes. SERS-based molecular detection can be achieved by using metal (mostly silver and gold) nanostructures as plasmonic antennas to amplify the Raman signals. While the enhanced Raman scattering by the nanohole arrays is mainly attributed to excitations of propagating surface plasmons via grating coupling, the nanoparticle arrays share the similar enhancement mechanism as individual nanostructures with excitations of LSPs. In addition, dealloyed nanoporous metals have also been exploited as attractive Raman-active structures because of their large surface area and three-dimensional (3D) bicontinuous porous configuration. Such unique features not only allow for excitations of LSPs but also provide a large number of molecular binding site.