Aqueous solutions of colloidal nickel: Radiation-chemical preparation, absorption spectra, and properties

Article abstract of DOI:10.1007/BF02496340

Radiation-chemical reduction of Ni²⁺ ions in aqueous solutions of Ni(ClO₄)₂ containing sodium formate or isopropyl alcohol was studied, γ-Irradiation of deaerated solutions in the presence of polyethyleneimine, polyacrylate, or polyvinyl sulfate gives stable metal sols containing spherical particles 2-4 nm in diameter. The optical absorption spectra of nickel nanoparticles exhibit a band with a maximum at 215±5 nm (ε₂₁₅ = 4.7 · 10³ L mol^-1 cm^-1) and a shoulder at 350 nm. A mechanism for the radiation-chemical reduction of Ni²⁺ ions by hydrated electrons and organic radicals (CO₂^- radical anions in the case of HCOONa and Me₂COH radicals in the case of Pr¹OH). The redox potentials of the Ni²⁺/Ni⁰ and Ni⁺/Ni⁰ pairs (Ni⁰ is a nickel atom) are approximately -2.2 and -1.7 V, respectively. The nanoparticles are readily oxidized by O₂, H₂O₂, and other oxidants. The reactions of these species with silver ions yield relatively stable nanoaggregates containing both nickel and silver in addition to silver nanoparticles.