title: Iron oxyhydroxide colloid formation by gamma-radiolysis.
abstract: Gamma-irradiation of deaerated aqueous solutions containing FeSO(4) leads to the formation of uniform-sized colloidal particles of γ-FeOOH. At short irradiation times, or in solutions with a low initial [Fe(2+)](0), spherical particles with a size less than 10 nm are formed. These primary particles grow to form a dendritic structure upon longer irradiation, and the final size of the large particles is ∼60 nm with a very narrow size distribution. Further prolonged irradiation does not change the final particle size. The narrow size distribution is attributed to rapid homogeneous radiolytic oxidation of soluble Fe(2+) to relatively insoluble Fe(3+) hydroxides [Fe(H(2)O)(6-n)(OH)(n)](3-n) leading to particle nucleation by spontaneous condensation. These primary particles then grow into γ-FeOOH particles with a dendritic structure. The final size reached at long times is regulated by the steady-state redox conditions established during long-term irradiation at the aqueous-solid interface.
authors.affiliation: Department of Chemistry, the University of Western Ontario, London, Ontario, Canada N6A 5B7.
authors.forename: P A
authors.initials: PA
authors.lastname: Yakabuskie
authors.forename: J M
authors.initials: JM
authors.lastname: Joseph
authors.forename: P
authors.initials: P
authors.lastname: Keech
authors.forename: G A
authors.initials: GA
authors.lastname: Botton
authors.forename: D
authors.initials: D
authors.lastname: Guzonas
authors.forename: J C
authors.initials: JC
authors.lastname: Wren