Surface plasmon polaritons (SPPs) are responsible for exotic optical phenomena including negative refraction, surface enhanced Raman scattering, and nanoscale focusing of light. Although many materials support SPPs, the choice of metal for most applications has been based on traditional plasmonic materials (Ag, Au) because there have been no side-by-side comparisons of the different materials on well-defined, nanostructured surfaces. Using a platform based on large-area arrays of nanopyramids, we have provided the first comparison of traditional and relatively unexplored plasmonic materials. These results generated threesurprises: (1) the narrowest surface plasmon resonances to date (which also correlate with the highest observed refractive index sensitivities); (2) surface plasmon coupling efficiencies of weak plasmonic materials (Cu and Al) that exceed those of strong plasmonic materials (Ag and Au) under certain conditions; and (3) nanopatterned Pd substrates that were more sensitive than Ag ones for detecting biomolecules.
