engleski

Experimental factors that may influence the γ- irradiation synthesis of magnetic iron oxide nanomaterials

Magnetic iron oxides are used for various applications, such as pigments, catalysts, in drug delivery, and hyperthermia cancer treatments. The chemistry of iron oxides is very diverse, due to the high versatility of iron in aqueous media. Two stable oxidation states (+2 and +3) and their relative concentrations and properties in aqueous media profoundly affect the end product of the synthesis. Although the chemistry of iron oxides is relatively complex, there are numerous works concerning their synthesis and characterizations. On the other hand, the radiolytic synthesis of magnetic iron oxide nanoparticles is much less investigated. Generally, γ-irradiation synthesis is an attractive and ecologically friendly technique for the synthesis of various nanomaterials including magnetic ones. It has the advantage of inducing electrons and other reducing species homogeneously throughout the system. The properties of the final magnetic material crucially depend on the particle size, dispersion, and aggregation. Various polymers can be used as stabilizers of magnetic nanoparticles in suspensions and as growth and surface modifiers. In this work, iron(III) chloride deaerated alkaline aqueous suspensions were γ-irradiated in the presence of 2-propanol and polymer stabilizer. We investigated the effect of different polymers (dextran and its cationic (DEAE-dextran) and anionic (dextran sulfate) derivatives, poly(ethylene oxide) (PEO), polyvinylpyrrolidone (PVP) and poly(vinyl alcohol) (PVA). Furthermore, the effect of irradiation dose, pH, polymer molecular mass and concentration, iron(III) precursor and 2-propanol concentration on the reduction of iron(III) to iron(II) upon irradiation, as well as the accompanied phase transformation of iron(III) precursor was investigated. The variation of experimental conditions strongly influenced the amount of reduced iron(III), and subsequently the phase composition, morphology, and size of formed nanoparticles. The higher pH values (12 vs. 9) contributed to a better reduction of Fe(III) in the presence of PEO, while the opposite behavior was observed for all other polymers. The initial concentration of DEAE- dextran significantly affected the reduction ; complete reduction occurred at 0.35% polymer concentration, whereas it decreased by ~40% when DEAE-dextran concentration was 10%, at the same dose. Average molecular mass had almost no effect in the case of dextran (40.000 vs. 500.000), whereas a small improvement of reduction was observed for lower molecular mass PEO (35.000 vs. 400.000). Iron(III) precursor and 2-propanol concentration also influenced reduction and phase composition. Furthermore, dextran polymers, especially DEAE-dextran, completely stabilize the precursor particles forming colloidal solutions before irradiation. In the case of DEAE-dextran, the phase composition of formed nanoparticles was predominantly magnetite or magnetic δ-FeOOH nanoparticles depending on the absorbed dose. In the case of dextran sulfate, a multiphasic system was obtained in all cases. On the other hand, upon irradiation in the presence of PEO, PVP, and PVA, the magnetic suspensions or magnetic nanocomposite hydrogels were formed depending on the initial conditions. Due to the lower reduction achieved in the case of PEO and PVP, magnetite and goethite were the predominant phases even at very high doses.

magnetic hydrogel ; gamma-irradiation ; poly(ethyleneoxide) ; dextran ; poly(vinylpyrrolidone) ; Fe(II)determination ; XRD

nije evidentirano