Synthesis route to δ-FeOOH nanodiscs

delta-FeOOH is a synthetic analogue of a relatively uncommon mineral feroxyhyte (delta'-FeOOH). The conventional syntheses of delta-FeOOH start from the Fe(II) salt and proceed by a rapid oxidation of iron(II) hydroxide with H2O2. The new synthesis route to delta-FeOOH nanodiscs reported in this work is based on the gamma-irradiation of a deoxygenated iron(III) chloride alkaline aqueous colloidal solution in the presence of 2-propanol and diethylaminoethyl-dextran hydrochloride (DEAE-dextran). gamma-irradiation of the colloidal solution enabled the strong reducing conditions thus favouring the reduction of Fe(III) to Fe(II). Under such strong reducing conditions the white suspension characteristic of Fe(OH)(2) was formed. When the white suspension came into contact with oxygen from air it rapidly oxidized into stable green-gray suspension characteristic of Fe(II)-Fe(III) hydrochloride known as Green Rust I. In the conventional process of sample isolation the green-gray stable suspension transformed to delta-FeOOH reddish powder that consists of rather uniform regular nanodiscs. The synthesized delta-FeOOH nanodiscs are magnetic and contain a magnetically ordered component in the Mossbauer spectrum at room temperature. It is expected that the results of this work will have a strong impact on finding new synthetic routes to the delta-FeOOH. (C) 2016 Elsevier B.V. All rights reserved.