Spinel-Structured Nanoparticles and Their Composites: From Synthesis to Perspective Applications

Dear Colleagues,

This Special Issue will focus on new developments in the synthesis and complex characterization of spinel-structured nanoparticles and their composites as nanomaterials with outstanding promising application properties. At present, spinel ferrite nanoparticles (SF-NPs) adopting the general MFe₂O₄ formula with M = 3d element are being intensively studied due to their applications (e.g., magnetic memory storage devices, permanent magnets, magnetic fluid technology, electronic devices, as well as photocatalytic and biomedical applications). The control of NPs’ crystal structure and microstructure is conducted by applying several synthesis methods, allowing the design and production of nanoparticles without the drawbacks typical of their bulk counterparts. The applied type of confinement leads to possible tailoring of various properties typical at nanoscale, such as superparamagnetism (SPM), so-called core–shell structure, or spin glass systems. Many investigations of SF-NPs have recently paid attention to Ni-Zn-based nanoferrites, revealing a high resistivity, high permeability, high values of saturation magnetization and Curie temperature, high mechanical hardness, as well as excellent chemical stability and dielectric properties. Thus, these NPs have been natural candidates as components for the production of nanohybrids. Other candidate include graphene oxide (GO) and carbon nanotubes (CNTs). Graphene oxide, as a 2D nanomaterial in a combination of SF-NPs, offers a large contact surface for the homogeneous distribution of NPs, and improves the dielectric and magnetic losses. Carbon nanotubes, as a 1D nanomaterial, exhibit outstanding mechanical and structural properties, high length/diameter ratio, high electrical conductivity, and excellent chemical and thermal stability. All the above factors make GO and CNTs ideal building blocks for nanohybrids. As proved, both can be satisfactorily tested for possible applications as, e.g. high magnetic hyperthermia prospects novel drug delivery materials due to thermal, mechanical stability and high biocompatibility or microwave-absorbing materials due to better impedance matching and in a tunable high-mobility charged carrier with increased dielectric and magnetic losses. There are also other composite materials, such as core/shell structures (e.g. SF-NPs encapsulated in an amorphous SiO₂  matrix), which enhance the thermal and chemical stability of magnetic nanoparticles, providing a chemically inert surface allowing for further functionalization. The stabilizing role of the silica shell protects the metallic core from any modification or degradation during subsequent heat treatment. In this way, the properties of the obtained compounds can be modified by annealing, which is a crucial factor for the controlled tailoring of the structural and magnetic properties. These nanohybrids are among the most studied as magnetic hyperthermia candidates.

This Special Issue is welcomes papers addressing topics including but not limited to spinel ferrite nanoparticles (SF-NPs) adopting the normal or inverse MFe₂O₄ structure and their composites, and invites a wide range of research on various spinel-structured nanoparticles and/or their composites, from synthesis and characterization to potential application.

I invite you to submit a manuscript for this Special Issue. Full articles, short communications, and review papers containing experimental and theoretical studies are welcomed.

Dr. Anna Bajorek
Guest Editor

Manuscript Submission Information

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• spinel-structured
• ferrite
• nanoparticles
• composites
• synthesis
• characterization
• applications