Reduction of Ag+ on polyacrylate chains in aqueous solution

Silver ions are reduced in aqueous solutions that contain sodium polyacrylate or partly carboxylated polyacrylamide or glutaric acid. The reducing agent is the hydrated electron (generated gamma-radiolytically) or hydrogen. Complexes of small silver clusters with the polyelectrolyte are formed in the early stages of reduction, the color of the solutions varying from rose to green or blue depending on the size of the complexed silver clusters. In the case of 10% carboxylated polyacrylamide, large colored complexes are not formed, which indicates that a high carboxylate density along the polymer chain is necessary for their formation. The complexes are stable toward heat (100 degrees C) and oxygen. In the later stages of reduction, the long-wavelength absorptions of the silver-polyacrylate complexes disappear. The UV absorption bands of a magic cluster (probably Ag-9(+)) are present during a short time interval, until the plasmon absorption band of metallic nanoparticles develops at 380 nm. The colored clusters react with ammonia and cyanide to form large silver particles through the intermediate stage of the magic cluster.