SIZE TAILORING OF SILVER COLLOIDS BY REDUCTION IN W/O MICROEMULSIONS

Colloidal silver particles of different sizes and size distributions have been prepared by reduction of aqueous silver salt solution in a reversed micellar system. The micelles in cyclohexane were stabilized by the non-ionic surfactant dodecyl-pentaethyleneglycol-ether; NaBH4 solutions were used for the reduction. To achieve different diameters of the silver particles, the water/surfactant ratio was varied. The sols were characterized by absorption spectroscopy, and particle sizes were determined from electron micrographs. The absorption spectra were modeled by the electromagnetic theory of localized surface plasmon excitation, using the experimentally determined size distribution of the particles. Quantitative agreement between experimental and calculated absorption maxima was obtained when a size-dependent ionic layer on the surface of the particles was included into the calculations. © 1992.