Template Synthesized Nanoscopic Gold Particles: Optical Spectra and the Effectsof Particle Size and Shape

摘要

We have prepared nanoscopic gold cylinders of controlled radius and aspect ratiovia electrodeposition of the metal within the pores of anodically-grown porous aluminum oxide membranes. The nanocylinder radii are determined by the pore dimensions of the host alumina which, in turn, depend on anodization conditions. The particle aspect ratios were controlled by varying the amount of Au deposited within the pores The optical spectra of the gold nanocylinder/alumina composites exhibit strong absorption bands in the visible spectrum. The extinction maxima (Lambda max) values for gold particles approaching sphere-like geometry agree well with Mie Theory calculations. The blue shift of (Lambda max) as the particle aspect ratio is increased is in qualitative agreement with Maxwell-Garnett Theory. We propose a simple modification of Maxwell-Garnett Theory that addresses both size and shape effects. Nanometals, Nanomaterials, Maxwell-Garnett theory.