Catalytic and SERS activity of SPION/Ag and SPION/Au nanostructures synthesized using γ-irradiation

In this work, γ-irradiation was used as an effective and environmentally friendly technique for the synthesis of superparamagnetic iron oxide/Ag (SPION/Ag) and iron oxide/Au nanostructures (SPION/Au). Such hybrid particles have promising applications and advantageous properties due to combination of unique magnetic, electric and optical properties. Alkaline iron(III) precursor solutions, with addition of 2- propanol and DEAE dextran, were purged with nitrogen and γ-irradiated to doses of 14 and 75 kGy, resulting in the reduction of Fe3+ to Fe2+ ions and formation of magnetite (14 kGy, 33% reduction) or Fe(OH)2 (75 kGy, 100% reduction). After irradiation, gold (AuNPs) or silver (AgNPs) nanoparticles were attached to the surface of the magnetic NPs by in situ reduction of Au3+ or Ag+ with radiolytically formed Fe2+. At 75 kGy, the simultaneous oxidation of Fe(OH)2 formed on irradiation and reduction of Au3+ or Ag+ (as confirmed by additional irradiation experiments) led to the formation of superparamagnetic feroxyhyte (δ-FeOOH) nanodiscs decorated with well distributed small AuNPs or AgNPs. The synthesized SPION/Au and SPION/Ag showed high catalytic efficiency in reducing the highly toxic organic pollutant 4-nitrophenol to the commercially important substance 4 aminophenol. The catalytic activity depended on concentration and size of Au (Ag) NPs on the surface. The synthesized hybrid NPs also showed promising SERS activity for the detections of low concentrations of organics in aqueous solutions. δ-FeOOH/Ag NPs enabled good SERS enhancement and detection of up to 10-6 M of 4-MBPA. Acknowledgments: This work has been supported by the Croatian Science Foundation under the project UIP-2017-05-7337 (POLRADNANOP), and Croatian-Slovenian project “Radiolytic synthesis of magnetic δ-FeOOH@Au designed for biomedical applications“