UV/Visible and infrared spectra of polyethylene/nanoscopic gold rod composite films: effects of gold particle size, shape and orientation.

We have prepared nanoscopic gold rods of various radii and aspect ratios via anodic aluminum oxide - based template synthesis, and incorporated these particles into polyethylene films. The resulting composite films exhibit linear dichroic properties which result from a net orientation of the rods. The plasmon resonance absorption maxima occur at the longest wavelengths when the incident electric field is polarized along the direction of particle orientation, and are blue-shifted as the polarization angle is directed perpendicular to the orientation direction. These results are in general accord with Rayleigh scattering theory, though effective medium type approaches which account for inter-particle interaction yield a closer quantitative agreement. We will also discuss the application of these composite materials to surface-enhanced infrared spectroscopy.