Optical properties of aligned rod-shaped gold particles dispersed in poly(vinyl alcohol) films

The polarization spectra of template-synthesized colloidal gold rods with a spect ratios ranging from L/d = 1.8 to 49 (and a diameter d = 15 nm) embedd ed in poly(vinyl alcohol) (PVA) films are studied as a function of the film elongation. Orientation of the colloidal gold rods is obtained by stretchi ng the PVA films. The polarization absorbance spectra of aligned systems sh ow only one resonance band instead of two absorbance bands as found for ran domly distributed gold rods. The visible and near-infrared spectra reveal t hat the rods are completely oriented when the film is stretched 4-6 times i ts original length. No significant effect of the aspect ratio is observed o n the film elongation required for complete alignment. The alignment of gol d rods by the stretched-film method is visualized by reflection confocal sc anning laser microscopy (CSLM). The CSLM micrographs also demonstrate the d istribution of single gold rods in the film.