Dielectric constants of silver particles finely dispersed in a gelatin film

Optical properties of gelatin with a very low concentration of silver particles were studied in the region from 300 to 800 nm. Such samples clearly showed isotropic properties and offered the advantage of having well-separated and noninteracting silver particles. Detailed optical constants for the gelatin matrix have been determined and their use, via the Mie theory, has enabled the determination of the dielectric constants and the loss function for the metallic particles themselves. An apparent blue shift in the plasma resonance absorption has been observed with the loss function when the particle size varied from 22 to 10 nm. Experimental data of this nature are needed for meaningful comparison between theory and experiment.