engleski

A controllable method for the synthesis of magnetic iron oxide and iron oxide/Au nanostructures using γ-irradiation

Magnetic iron oxide nanoparticles (MNPs) due to their unique magnetic and electrical properties have applications as sensor, contrast agents, in drug delivery and for hyperthermia cancer treatments. In this work we have used γ- irradiation as an attractive and ecologically friendly technique for the synthesis of magnetic nanoparticles at room temperature. γ- irradiation has an advantage of inducing electrons and other reducing species homogeneously through the sample. We have systematically studied the influence of γ- irradiation dose on the synthesis of iron oxide nanoparticles. The iron(III) chloride alkaline aqueous solutions were purged with nitrogen and g-irradiated with addition of 2-propanol. DEAE- dextran was used as growth and stabilizing agent of MNPs in suspensions. The phase composition, stoichiometry and morphology of MNPs were controlled by adjusting γ-irradiation dose and dose rate. Irradiation with doses 10 - 36 kGy resulted in the formation of very small 4 nm spherical substoichiometric magnetite NPs, whereas at higher dose (50 kGy or more) the major phase was magnetic δ-FeOOH (feroxyhyte) in the form of nanodiscs. The magnetic measurements showed superparamagnetic behaviour of magnetite NPs and exceptional intrinsic room-temperature magnetic properties of δ-FeOOH nanostructures with the Curie temperature above 300 K. The reduction of ferric (Fe3+) to ferrous (Fe2+) ions was quantitatively determined using the 1, 10-phenanthroline spectrophotometric method. The reduction proceeds fast in the beginning stages of irradiation (up to 30 kGy, ~65% Fe3+ reduced), slows down after this initial period, and reaches 100% reduction at ~75 kGy. However, ferrous ions (Fe2+) that formed upon g- irradiation of iron(III) precursor in the form of intermediate Fe(OH)2 were highly susceptible to oxidation and in the contact with air oxidized to Green Rust (formula) and further upon isolation to δ-FeOOH nanodiscs. Furthermore, the possibility to use γ- irradiation to form iron oxide/Au nanostructures was explored.

gamma-irradiation ; amino dextran ; dextran sulfate ; poly(ethylene oxide) ; feroxyhyte ; magnetite

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