title: Radiation-induced pink nickel oligomeric clusters in water. Pulse radiolysis study.
abstract: γ-rays and pulse radiolysis of aqueous solutions of Ni(2+) ions in the presence of polyacrylate (PA(-)) and 2-propanol leads to the formation of metastable species absorbing at 540 nm that are ascribed to "pink" oligomeric clusters of a few nickel atoms only. The molar absorption coefficient is evaluated as ε540 nm = 3300 ± 300 L mol(-1) cm(-1) per Ni(0) atom. The successive steps from the reduction of Ni(2+) into Ni(+) ions to the formation of the pink clusters at 540 nm under conditions of complexation by PA(-) are investigated by pulse radiolysis. The yield of the formation of pink clusters increases markedly with the irradiation dose rate, demonstrating the occurrence of the disproportionation of the [Ni(+), PA(-)] complex after a single electron pulse. The reduction and nucleation mechanisms, including rate constants, in competition with the back oxidation by protons, particularly at low dose rate, are discussed.
authors.affiliation: Laboratoire de Chimie-Physique, UMR 8000 CNRS-UPS, Bâtiment 349, Université Paris-Sud , 91405 Orsay-cedex, France.
authors.forename: Mohamed Larbi
authors.initials: ML
authors.lastname: Hioul
authors.forename: Mingzhang
authors.initials: M
authors.lastname: Lin
authors.forename: Jacqueline
authors.initials: J
authors.lastname: Belloni
authors.forename: Nassira
authors.initials: N
authors.lastname: Keghouche
authors.forename: Jean-Louis
authors.initials: JL
authors.lastname: Marignier