Synthesis and linear optical properties of nanoscopic gold particle pair structures

particle nanostructures were prepared in porous anodic aluminum oxide films via a modified template synthesis procedure. By varying the interparticle distance of centrosymmetric gold spherical particles (radius ca. 32 nm), the linear UV/visible polarization spectra of the gold particle/porous alumina film composites can be altered. The resulting spectra can be explained qualitatively in terms of particle electromagnetic interactions within an individual pore through simple quasistatic limit scattering models. Modified long wavelength approximation and discrete dipole approximation methods yield similar calculated spectra, and neither approach quantitatively describes the experimental spectra. Discrepancies are interpreted to arise in part from a distribution of interparticle spacings in the experimental system. Rod, rod-pair, and rod-sphere gold nanoparticle structures were also synthesized. Possible evidence for interaction between the two members of the rod-sphere structure is seen in the experimental spectra. The polarization spectra of the rod-containing systems are also only qualitatively described by quasistatic limit models.