Screening Plasmonic Materials using Nanopyramidal Arrays – Teri Odom

Date: Mon. April 6th, 2009, 12:30 pm-1:30 pm
Location: Rockefeller 221

Surface plasmon polaritons (SPPs) are responsible for 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 such as Ag and Au because there have been no side-by-side comparisons of different materials on well- defined, nanostructured surfaces. This talk will describe a platform that not only enables rapid screening of a wide range of metals under different excitation conditions and dielectric environments but that also can identify unexpected materials for biosensing. Nanopyramidal gratings were used to generate SPP dispersion diagrams for Al, Ag, Au, Cu and Pd. Surprisingly, the SPP coupling efficiencies of Cu and Al exceed widely used plasmonic materials under certain excitation conditions. Furthermore, grazing angle excitation can produce the highest refractive index sensitivities at optical frequencies because of extremely narrow SPP resonances (full- width-at-half-minimum < 6 nm). The screening process has also revealed that Ag, with the highest sensitivity, is not necessarily the ideal material for detecting molecules. Au, and even Pd, a weak plasmonic material, show comparable wavelength shifts upon formation of a protein monolayer.