γ-irradiation generated ferrous ions affect the formation of magnetite and feroxyhyte

• Published in: Radiation physics and chemistry (Oxford, England : 1993) Vol. 170; p. 108648
• Main Authors: Marić, I., Gotić, M., Štefanić, G., Pustak, A., Jurkin, T.
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01.05.2020; Elsevier BV
• Subjects: 1,10-Phenanthroline; Aqueous solutions; Aspect ratio; Crystallization; DEAE-Dextran; Dextrans; Diethylaminoethyl dextran; Feroxyhyte; Ferrous ions; Gamma irradiation; Magnetite; Nanoparticles; Radiation dosage; Reduction; Spectrophotometry; Stoichiometry; Synthesis; Gamma-irradiation; 1,10-Phenanthroline; Feroxyhyte; DEAE-Dextran; Magnetite
• ISSN: 0969-806X; 1879-0895
• DOI: 10.1016/j.radphyschem.2019.108648

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 products 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 69% or more of Fe2+ the powder samples consisted exclusively of Fe(III), i.e. of δ-FeOOH nanodiscs and poorly crystallized α-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. •γ-irradiation generated Fe2+ was quantitatively measured using 1,10-phenanthroline.•Fe2+ generated initially very quickly and then slowed down to reach a value of 100%.•Magnetite formed when γ-irradiation generated between 22 to 69% of Fe2+ in suspension.•DEAE dextran and at least 69% of Fe2+ are crucial for synthesis of δ-FeOOH nanodiscs.