A gamma irradiation method for the synthesis of iron oxide/gold nanostructures

Magnetic iron oxide nanoparticles (MNPs) due to their unique magnetic and electrical properties have applications as sensors, contrast agents, in drug delivery, hyperthermia cancer treatments, etc. For these uses, the surface of the particles should be modified with a suitable surface coating that can easily bind the appropriate biomolecules for the selected application. Gold has become one of the favored coatings because it is non-toxic, biocompatible, chemically inert, enables additional functionalization and can protect MNPs from oxidation without significantly reducing magnetic properties. In this work, we have used γ- irradiation as an attractive and ecologically friendly technique for the synthesis of magnetic composite nanoparticles at room temperature. The phase composition, stoichiometry, and morphology of MNPs were controlled by adjusting the γ- irradiation dose. Irradiation with doses 10–36 kGy resulted in the formation of very small 4 nm spherical magnetite NPs, whereas at a higher dose (50 kGy or more) the major phase was magnetic δ- FeOOH (feroxyhyte) in the form of nanodiscs. The Au nanoparticles formed were spherical ; the quantity and size of Au nanoparticles depended on the amount of initially added HAuCl4 aqueous solution. In this way, it was possible to obtain magnetic spherical magnetite/Au and thin nanodisc δ-FeOOH/Au nanostructures (Figure 1) from the same starting suspension by varying just one experimental factor: the absorbed dose.