THE NUCLEATION OF COLLOIDAL COPPER IN THE PRESENCE OF POLY(ETHYLENEIMINE)

Copper colloids have been prepared by gamma-radiolysis of cupric ions in the presence of poly(ethyleneimine). The reduction takes place in t wo, distinct steps. Copper (II) is reduced quantitatively to copper (I ), and then nucleation of the colloid occurs after an induction period . The nucleation of colloidal copper is catalysed by the presence of l ess noble Pb(II) or Tl(I) ions, which is explained by the generation o f Pb and Tl nuclei in the solution, and their subsequent reoxidization by Cu(I). The formation of copper colloids is also catalysed by the p resence of colloidal silver or silver ions, and radiolysis results in the formation of copper coated silver colloids. The optical shifts obs erved during the deposition of copper on silver cannot be explained by Mie theory, The differences are suggested to be due to weaker interba nd transitions in the copper monolayers than in the bulk metal.