Selective magnetometry of superparamagnetic iron oxide nanoparticles in liquids

Abstract

A new photon-in/photon-out magnetic probe empowers an in situ estimation of size distribution and atomic structure of iron oxide nanoparticles in suspension.

Effect of Thermal Treatment at Inert Atmosphere on Structural and Magnetic Properties of Non-stoichiometric Zinc Ferrite Nanoparticles

“…When the particle size decreases, the composition of ZF is altered, leading to the occurrence of superparamagnetism or ferrimagnetism at room temperature. [5,[22][23][24][25][26][27][28][29] This is mainly related to the redistribution of cations in the lattice, which occurs when grain sizes are decreased to nanoscale. [24,[30][31][32] In contrast to bulk ZF (of normal spinel structure), nanoparticles of stoichiometric zinc ferrite (ZF NPs) reveal a mixed spinel structure, where Zn 2+ and Fe 3+ cations are distributed between () Td and [] Oh sites.…”

X-ray-Based Techniques to Study the Nano–Bio Interface

“…Thus far, the method was successfully applied to shed light on weak noncovalent bonding of CO 2 to NPs, the roles of a central carbon in the nitrogenase iron–molybdenum cofactor, and photocatalysis. − Furthermore, the implementation of high-energy-resolution spectrometers facilitates measurements of hard X-ray magnetic circular dichroism combined with resonant inelastic X-ray scattering (RIXS-MCD) on magnetic NPs relevant in biomedical applications as contrast agents. The RIXS-MCD method enables the determination of the size distributions of superparamagnetic iron oxide NPs in frozen samples and in concentrated solutions, which are below the detection limits of light-scattering probes. − …”

Thermal Decomposition Pathways of ZnxFe3–xO4 Nanoparticles in Different Atmospheres

“…Comprehensive approach to design and synthesis of nanomaterials significantly widened possibilities of their application throughout vast life areas. − Nanoparticles with magnetic properties have been very interesting materials for basic research and technological applications for years. − The special attention of scientists is on ferrite nanoparticles with a spinel structure: (M 1– x Fe x )­[M x Fe 2– x ]­O 4 , where the parentheses and square brackets denote the (tetrahedral) and [octahedral] sites (later Td and Oh, respectively), and M is a transition metal (for example, Zn, Mg, Co, or Fe). ZnFe 2 O 4 nanoparticles (ZFN) are the subject of investigation, because of their unique magnetic properties, memory effect, superspin-glass ordering, low toxicity, specific microwave absorption, electrical properties, and photocatalytic activity. ,− ,,,, …”

“…Ferrites of a spinel structure provide a possibility of controlling chemical and physical properties. ,,, On the nanoscale, at room temperature (RT), ZFN reveal superparamagnetic response, while at a cryogenic temperature of −268 °C (∼5 K), they show ferrimagnetic properties. ,,− Alterations are possibly caused by, e.g., the nanoparticle size, applied magnetic field, or dipole–dipole interactions. , …”

“…The magnetic, electronic, and optical properties of spinel ferrites all are dependent on changes in sizes and distributions of cations in the crystal lattice, from the bulk zinc ferrite (ZF), to the normal-inverse mixed spinel structure, characteristic for nanoparticles. ,,− The magnitude of this effect is parametrized by the degree of inversion (σ) quantifying the distribution of M 2+ and Fe 3+ cations among Td and Oh sites, e.g., (Zn 1−σ Fe σ )­[Zn σ Fe 2−σ ]­O 4 in perfectly normal spinel structure means σ = 0. σ is dependent on the relative sizes of cations, their charges, and the relative crystal-field stabilization offered by the tetrahedral or octahedral coordination. ,− …”