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 scatter ing are recorded. When iodide adsorbs on the silver particles, the 225 -nm band of I- disappears concurrently with the decreasing of the silv er plasmon absorption band. In the same time range, the intensity of L ight scattering slightly decreases, which is explained as a detachment of the colloidal particles from the polyphosphate stabilizer. At a la ter stage, the silver plasmon band is red-shifted and the light scatte ring finally increases again, which is understood in terms of loose cl uster formation of the particles. The adsorption of H2S leads to dampi ng and a simultaneous blue shift of the plasmon absorption band. The a dsorption of H2S is faster than that of SH-, as there is no Coulomb re pulsion between the adsorbant and the negatively charged metal particl es.