Reactions of radicals with hydrolyzed Bi(III) ions: a pulse radiolysis study

Radiolytic reduction of BiOClO4 in aqueous solutions leads to the formation of bismuth clusters and larger nanoparticles. The mechanisms of redox reactions of the polycationic Bi(III) species that exist in the solution were investigated with pulse radiolysis. The kinetic and spectral properties of the transients formed by the reaction of these species with the primary radicals from water radiolysis are reported. The single-electron reduction product, Bi9(OH)224+, absorbs at lambdamax = 273 nm, while the OH adduct, Bi9(OH)235+, has a broad absorption spectrum with a maximum at 280 nm and a shoulder at 420 nm. Several rate constants were measured: k (e-aq + Bi9(OH)225+) = 1.2 x 1010 M-1 s-1 and k (OH + Bi9(OH)225+) = 1.5 x 109 M-1 s-1. The reduced species, Bi9(OH)224+ further reacts with (CH3)2COH radicals, but not with CH2C(CH3)2OH radicals from t-butanol, to produce a doubly reduced polynuclear species. A few reactions of the reduction of the Bi salt in the presence of poly(acrylic acid) are also described. In the presence of the polymer, a metal-polymer complex is formed prior to the irradiation, and the reduction reactions are significantly slowed down.