Gold nanorod extinction spectra

Geometrical factors suitable for use in Mie-Gans theory are derived from discrete dipole aproximation generated spectra for a number of pseudonanorods permitting the rapid calculation of extinction spectra. It is shown that the rod width, rod end-cap geometry (flat, oblate spheroid, and sphere) and the rod size distribution all have a significant effect on the position of the peak absorbance. Moreover, it is shown that spectrometric characterization of nanorods is possible given an independent measure of rod width and suitable assumptions regarding the end-cap geometry and the form of the rod-length distribution; under such conditions the full width half maximum and the extinction peak uniquely determine the average rod length and the breadth of the distribution. (c) 2006 American Institute of Physics.