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Zn²⁺ Ion Surface Enrichment in Doped Iron Oxide Nanoparticles Leads to Charge Carrier Density Enhancement.

ABSTRACT: Here, we report the development of monodisperse Zn-doped iron oxide nanoparticles (NPs) with different amounts of Zn (Zn _x Fe_3-x O₄, 0 < x < 0.43) by thermal decomposition of a mixture of zinc and iron oleates. The as-synthesized NPs show a considerable fraction of wüstite (FeO) which is transformed to spinel upon 2 h oxidation of the NP reaction solutions. At any Zn doping amounts, we observed the enrichment of the NP surface with Zn²⁺ ions, which is enhanced at higher Zn loadings. Such a distribution of Zn²⁺ ions is attributed to the different thermal decomposition profiles of Zn and Fe oleates, with Fe oleate decomposing at much lower temperature than that of Zn oleate. The decomposition of Zn oleate is, in turn, catalyzed by a forming iron oxide phase. The magnetic properties were found to be strongly dependent on the Zn doping amounts, showing the saturation magnetization to decrease by 9 and 20% for x = 0.05 and 0.1, respectively. On the other hand, X-ray photoelectron spectroscopy near the Fermi level demonstrates that the Zn_0.05Fe_2.95O₄ sample displays a more metallic character (a higher charge carrier density) than undoped iron oxide NPs, supporting its use as a spintronic material.

SUBMITTER: Bram S

PROVIDER: S-EPMC6643693 | biostudies-literature | 2018 Nov

REPOSITORIES: biostudies-literature

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Zn2+ Ion Surface Enrichment in Doped Iron Oxide Nanoparticles Leads to Charge Carrier Density Enhancement.

Bram Stanley S Gordon Matthew N MN Carbonell Michael A MA Pink Maren M Stein Barry D BD Morgan David Gene DG Aguilà David D Aromí Guillem G Skrabalak Sara E SE Losovyj Yaroslav Y Bronstein Lyudmila M LM

ACS omega 20181130 11

Here, we report the development of monodisperse Zn-doped iron oxide nanoparticles (NPs) with different amounts of Zn (Zn x Fe3-x O4, 0 < x < 0.43) by thermal decomposition of a mixture of zinc and iron oleates. The as-synthesized NPs show a considerable fraction of wüstite (FeO) which is transformed to spinel upon 2 h oxidation of the NP reaction solutions. At any Zn doping amounts, we observed the enrichment of the NP surface with Zn2+< ...[more]

PMID: 31458268

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Project description:Magnetic nanoparticles (NPs) are powerful agents to induce hyperthermia in tumours upon the application of an alternating magnetic field or an infrared laser. Dopants have been investigated to alter different properties of materials. Herein, the effect of zinc doping into iron oxide NPs on their magnetic properties and structural characteristics has been investigated in-depth. A high temperature reaction with autogenous pressure was used to prepare iron oxide and zinc ferrite NPs of same size and morphology for direct comparison. Pressure was key in obtaining high quality nanocrystals with reduced lattice strain (27% less) and enhanced magnetic properties. Zn0.4Fe2.6O4 NPs with small size of 10.2 ± 2.5 nm and very high saturation magnetisation of 142 ± 9 emu gFe+Zn-1 were obtained. Aqueous dispersion of the NPs showed long term magnetic (up to 24 months) and colloidal stability (at least 6 d) at physiologically mimicking conditions. The samples had been kept in the fridge and had been stable for four years. The biocompatibility of Zn0.4Fe2.6O4 NPs was next evaluated by metabolic activity, membrane integrity and clonogenic assays, which show an equivalence to that of iron oxide NPs. Zinc doping decreased the bandgap of the material by 22% making it a more efficient photothermal agent than iron oxide-based ones. Semiconductor photo-hyperthermia was shown to outperform magneto-hyperthermia in cancer cells, reaching the same temperature 17 times faster whilst using 20 times less material (20 mgFe+Zn ml-1vs. 1 mgFe+Zn ml-1). Magnetothermal conversion was minimally hindered in the cellular confinement whilst photothermal efficiency remained unchanged. Photothermia treatment alone achieved 100% cell death after 10 min of treatment compared to only 30% cell death achieved with magnetothermia at clinically relevant settings for each at their best performing concentration. Altogether, these results suggest that the biocompatible and superparamagnetic zinc ferrite NPs could be a next biomaterial of choice for photo-hyperthermia, which could outperform current iron oxide NPs for magnetic hyperthermia.

Dataset Information

Zn²⁺ Ion Surface Enrichment in Doped Iron Oxide Nanoparticles Leads to Charge Carrier Density Enhancement.

Publications

Zn<sup>2+</sup> Ion Surface Enrichment in Doped Iron Oxide Nanoparticles Leads to Charge Carrier Density Enhancement.

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