Marić, Ivan; Gotić, Marijan; Štefanić, Goran; Pustak, Anđela; Jurkin, Tanja
(2020)
γ-irradiation generated ferrous ions affect the formation of magnetite and feroxyhyte.
Radiation Physics and Chemistry, 170
.
ISSN 0969-806X
Abstract
1, 10-phenanthroline spectrophotometric method was used in order to systematically measure the quantity of Fe2+ ions that were generated upon γ-irradiation of alkaline Fe(III) aqueous solutions in the presence of diethylaminoethyl (DEAE)-dextran. γ-irradiation was performed in a range of doses from 5 to 130 kGy and the dose rate was ~26 kGy h-1. The results showed that γ-irradiation reduces Fe3+ to Fe2+ ; the reduction was initially very fast, but quickly slowed down and then reached a plateau of 100 % reduction. The quantity of Fe2+ in γ-irradiated suspensions and isolated solid product roughly overlap up to 45 % of Fe2+, because in this range the inverse spinel structure of substoichiometric magnetite nanoparticles was able to capture 30.1 % of Fe2+. The stoichiometries of the formed magnetite nanoparticles were very similar, which indicated that the absorbed dose did not have a significant influence on the magnetite stoichiometry, even though Fe2+ molar fraction increased from 22 to 45 % as a function of absorbed dose. When γ-irradiation generated more than 45 % of Fe2+ the powder samples consisted exclusively of Fe(III), i.e. of δ-FeOOH nanodiscs and poorly crystallized δ-FeOOH nanoparticles about 4 nm in size. The volume-averaged domain sizes and crystal aspect ratio of the δ-FeOOH nanodiscs increased from 16 nm to 25 nm and from 1.6 to 2.1 with the increase of absorbed dose, respectively. The use of DEAE-dextran in the γ-irradiation synthesis enabled the generation of up to 100 % of Fe2+ and synthesis of extremely stable aqueous suspensions of superparamagnetic magnetite nanoparticles as well as the synthesis of δ-FeOOH nanodiscs with high aspect ratios.
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