KINETICS OF ELECTRON-TRANSFER TO CRITICAL SIZED SILVER CLUSTERS COMPLEXED BY POLYACRYLATE

Pulse radiolysis was used to observe the reactivity of an electron don or with respect to silver clusters complexed with silver ions and by p olyacrylate. As in a previous study concerning free aggregates, the de veloper, sulfonato-propylviologen anion, with a redox potential E(NHE) 0 = - 0.41 V, and the silver atoms were produced by the same pulse. As with the free aggregates, a critical size nc = 4 is necessary for the electron transfer to occur from sulfonato-propylviologen anion to the silver cluster (E0(Ag5+)/Ag5) greater-than-or-equal-to -0.41 V). Howe ver, the coalescence here being much slower than the electron transfer , the kinetics is drastically changed. As soon as the first critical c lusters appear, they are developed quickly, so that the donor is readi ly exhausted. The consequence is that the final distribution of cluste rs is divided into a minor fraction of heavy developed clusters and th e rest consisting of undeveloped oligomers. The rate constants for the electron transfer are found to be 2 x 10(8) and 5 x 10(7) L mol-1 sec -1, respectively, in neutral and acidic medium.