Magnetic δ-FeOOH/Au nanostructures synthesized using γ-irradiation method and their catalytic activity for the reduction of 4-nitrophenol

Abstract

γ-irradiation was used as an effective and environmentally friendly technique for the synthesis of magnetic iron oxide/Au nanostructures. Firstly, alkaline iron(III) precursor solutions, in the presence of 2-propanol and DEAE-dextran, were purged with nitrogen and γ-irradiated to doses of 14 and 75 kGy, which resulted in the reduction of Fe3+ to Fe2+ ions and formation of Fe(II)/Fe(III) or Fe(II) iron (hydr)oxide phases. After irradiation, gold nanoparticles (AuNPs) were attached to the surface of the magnetic nanostructures by in situ reduction of Au3+ with radiolytically formed Fe2+. At 75 kGy, simultaneous oxidation of Fe(OH)2 formed on irradiation and reduction of Au3+ led to the formation of superparamagnetic feroxyhyte (δ-FeOOH) nanodiscs decorated with well distributed, 11–24 nm AuNPs. The experiments performed with and without Fe(III) precursor and 2-propanol or tert-butanol as scavenger and in different atmospheres (N2, N2O) confirmed the main role of Fe2+ in Au3+ reduction. The catalytic activity of the δ-FeOOH/Au nanostructures was tested for the reduction of 4-nitrophenol to 4-aminophenol. Increasing the amount of added Au3+ enhanced the catalytic activity of the samples, but up to a certain amount depending on the size of formed AuNPs.