The impact of dextran sulfate on the radiolytic synthesis of magnetic iron oxide nanoparticles

Iron(III) chloride deoxygenated alkaline aqueous colloidal solutions in the presence of 2-propanol and dextran sulfate were gamma-irradiated with doses of 36 and 130 kGy. The dose rate was -31 kGy h(-1). The samples isolated by washing with water mainly consisted of gamma-FeOOH (lepidocrocite), delta-FeOOH and schwertmannite. The samples isolated by washing with ethanol contained mainly alpha-FeOOH (goethite), delta-FeOOH (feroxyhyte) and iron(III) hydroxide sulfate. At lower dose (36 kGy) magnetite (Fe3O4) was formed. The samples isolated by admixing glycerol consisted of the intermediate phases Fe(OH)(2), GR(SO42-) and non-stoichiometric FeSi1-x (mineral name mackinawite). The amounts of Fe(II) in glycerolisolated solid samples were 60.5% and 82.6% as determined by Mossbauer spectroscopy at doses of 36 and 130 kGy, respectively. The amount of Fe(2+)in the acidified solutions containing dissolved gamma-irradiation products was determined using potassium permanganate titration. The amounts of Fe(2+)in acidified solutions were 72.0% and 92.0% at doses of 36 and 130 kGy, respectively. Thus, although the conventionally isolated powders consisted exclusively of Fe(III) products, the high reducing conditions upon gamma-irradiation were confirmed by capturing the Fe(II) intermediate phases and by quantitative determinations of ferrous ions in the solid samples and solutions containing dissolved gamma-irradiation products. (C) 2019 Elsevier B.V. All rights reserved.