RADIATION-INDUCED COPPER AGGREGATES AND OLIGOMERS

Gamma radiolysis of CuSO4 solutions containing surfactants (polyvinyl alcohol, polyacrylic acid) induces the formation of copper nanoaggregates which dissolve readily when brought into contact with oxygen. The pink copper clusters and the intermediate Cu(I) are studied spectrophotometrically under various conditions: pH, Cu2+ concentration, radiolytic dose. The reactivity of the aggregates in redox reactions is used to determine, notwithstanding the presence of excess copper ions, the metal atom content and the radiolytic yield. The optical absorption band at 570 nm has thus been calibrated to be epsilon(Cu(n))570 nm = 1950 +/- 50 l mol-1 cm-1 at pH 6.2 and 2400 +/- 100 at pH 2.6. Oligomers of lower nuclearity stabilized by polyacrylate ions are shown to absorb at 292, 350 and 455 nm.