Investigation of structural, magnetic and catalytic properties of M1-xYx/Au-M1-xYx/Fe2O3 (M: Ni, Co; Y: Cu, Gd) chain-type core/shell magnetic nanoparticles (MNPs)

In this work, (FM)1-xYx, (FM)1-xYx/A core/shell and (FM)1-xYx/Au-(FM)1-xYx/Fe2O3 (FM: Ni and Co, Y: Cu and Gd, A: Au and α-Fe2O3) (0.0≤x≤0.25) chain-type core/shell magnetic nanoparticles (MNPs) were successfully synthesized by modified polyol reduction process. First of all, Cu and Gd were doped in the Ni and Co structures to determine appropriate Cu and Gd concentration. The structural, morphological, magnetic and electrocatalytic properties were examined of synthesizied core MNPs. Ni0.75Cu0.25, Ni0.95Gd0.05, Co0.85Cu0.15 and Co0.85Gd0.15 were determined as suitable core MNPs in terms of magnetic and catalytic properties. It was determined from XRD analysis of Ni-based core/shell chain-type MNPs synthesized using these cores that they have a cubic structure belonging to the Fm3 ̅m space group. It was determined that both hcp Co with P63/mmc space group and fcc Co crystal phases with Fm3 ̅m space group in Co-based ones were formed together. It was observed from SEM images that the chain structures tended to accumulate. From the temperature dependent magnetization (M-T) measurements ferromagnetic-paramagnetic phase transition was observed in Ni-based chain structure at near room temperature. From the magnetic field dependent magnetization (M-H) measurements, it was observed that Ni-based chain structures showed superparamagnetic behaviour at room temperature and their saturation magnetization (Ms) increased nearly two times compared to core MNPs at 300 K. No magnetic phase transition was observed from the M-T measurements of the Co-based chain structure. Accordingly, it was determined that there was no significant change in Ms values at 25, 100 and 300 K temperatures. In electrocatalytic measurements, it was observed that the hydrogen-evolution-reactions (HER) activity of chain-type structures was three times higher than that of core MNPs. The chain-type core/shell particle system synthesized in this thesis has been studied for the first time in the literature. The obtained experimental data show that there are canditate materials can be used in both magnetic and catalytic applications. Therefore, it is thought that the obtained data in this thesis will contribute significantly to the literature.