Time Resolved Chemisorption of I- and SH- on Colloidal Silver Particles (A Stopped-Flow Study)

An aqueous silver sol mean particle size 6 nm is mixed with KI and NaSH solution, and the changes in optical absorption and light scattering are recorded. When iodide adsorbs on the silver particles, the 225 nm band of I disappears concurrently with the decreasing of the silver plasmon absorption band. In the same time range, the intensity of Light scattering slightly decreases, which is explained as a detachment of the colloidal particles from the polyphosphate stabilizer. At a later stage, the silver plasmon band is red shifted and the light scattering finally increases again, which is understood in terms of loose cluster formation of the particles. The adsorption of H2S leads to damping and a simultaneous blue shift of the plasmon absorption band. The adsorption of H2S is faster than that of SH , as there is no Coulomb repulsion between the adsorbant and the negatively charged metal particles