Reduction of Ag(CN)(2)(-) on silver and platinum colloidal nanoparticles

Ag(CN)(2)(-) is reduced at a low rate by radiolytically generated hydroxyme thyl radicals. The reduction occurs on tiny nuclei in solution formed by hy drolysis. When colloidal silver seed particles are present in the solution, the reduction of Ag(CN)(2)(-) is much faster, and larger silver particles with a narrow size distribution are produced. A mechanism is proposed, in w hich the . CH2OH radicals transfer electrons to the seed particles, and the stored electrons finally reduce Ag(CN)(2)(-) directly on the surface of th e seeds. The limitations of this kind of radiolytic particle enlargement ar e discussed. In the presence of colloidal platinum, Ag(CN)(2)(-) is also ra pidly reduced by the organic radicals. Bimetallic particles of the PtcoreAg shell type with a rather nonsymmetric shape of the shell are formed; despit e this irregular structure, the optical spectra agree fairly well with lite rature spectra calculated for symmetric bimetallic particles.