BIMETALLIC AG-PT AND AU-PT AGGREGATES SYNTHESIZED BY RADIOLYSIS

Irradiating aqueous solutions containing both Ag2SO4 and K2PtCl4 leads to intermetallic aggregates of various sizes according to the stabili zing agent: polyvinylalcohol, polyacrylic acid or polyacrylate. In the last case, the particle diameter is 1.5 nm. The bimetallic character is evidenced in all cases by the spectral changes of such sols compare d to pure silver sols which display a characteristic surface plasmon a bsorption band. This plasmon band disappears when 10 to 20 at.% or mor e Pt is present. Observation by TEM gives an estimation of the particl e sizes. Comparable results have been obtained for Au-Pt particles.