Transient and Stable Silver Clusters Induced by Radiolysis in Methanol

The optical absorption spectra of Ag0, Ag2+, transient oligomers, and stable clusters were studied in deaerated methanol by pulse and γ-radiolysis methods and compared with data obtained from studies using other solvents. From the decay of e-solv at 620 nm, the formation rate constant of Ag0 was determined to be k(e-solv + Ag+) = (2.6 ± 0.6) × 1010 M -1 s-1. The coalescence rate of transient oligomers is particularly slow and the growth process is not completed within 2 s after the pulse. The surface plasmon band of stable clusters obtained by γ-radiolysis in methanol is intense and sharp (e385 nm = 1.8 × 104 M-1 cm-1). The clusters are readily oxidized by oxygen. By adding methyl viologen MV2+ to the solution containing stable silver clusters, the blue color of MV+• is transitorily observed, and the small clusters are developed into larger ones. Similarly, by pulse radiolysis of a mixture of silver cations and MV2+, silver atoms and MV+• are formed immediately through solvated electron scavenging, but su...