Ferromagnetic liquid crystals were predicted more than 40 years ago by Brochard in de Gennes. This work is the first experimental proof of their theory. Ferrimagnetic BaFe12O19 nanoplates are the basis of the ferromagnetic liquid crystal. Their synthesis was developed within the research program P2-0089. The crucial property of the incorporated magnetic nanoparticles is their plate-like shape that originates from their crystal structure, in addition to their size and magnetic properties. The synthesis of the applicable nanoparticles was developed under hydrothermal conditions in a combination with partial chemical substitution of Fe3+ with Sc3+. The final incorporation of the nanoparticles into a liquid crystal was made possible by the specific control of their surface properties. Due to the coupling between the liquid-crystal director and the magnetic moments of the nanoplates the optical properties of ferromagnetic liquid crystals can be tuned with electric or magnetic field.
COBISS.SI-ID: 27304231
Human epidermal growth factor receptor (EGFR) has emerged as an attractive target for cancer therapy. In this study, fluorescent, labeled magnetic, amino- or carboxyl-functionalized silica-coated maghemite nanoparticles were conjugated with epidermal growth factor (EGF) using different binding modes. The binding efficiency of EGF to the nanoparticles was measured by flow cytometry using specific anti-EGF antibody. The ability of EGF bioconjugates to target the EGF receptors was tested using EGFR over-expressing A431 cells in comparison to EGFR negative HeLa cells. Our results showed that bioconjugates where EGF was bonded by carbodiimide chemistry are the most effective for specific targeting of EGFR-expressing cells in vitro.
COBISS.SI-ID: 26704935
Bi-magnetic, platelet nanoparticles combining a hard-magnetic Ba-hexaferrite (BaFe12O19) platelet core in between two soft-magnetic iron oxide maghemite (-Fe2O3) layers were presented for the first time. The nanoparticles were synthesized using a new, simple and inexpensive method based on the co-precipitation of Fe3+/Fe2+ ions in a colloidal aqueous suspension of the hexaferrite core nanoparticles. The hexaferrite displays the highest magnetocrystalline anisotropy from all magnetic oxides, however, modest saturation magnetization. By combining the hexaferrite core with the soft magnetic shell in single nano-unit, the saturation magnetization can be strongly increased. Moreover, the topotactic growth of the maghemite shell on the hexaferrite core supported the direct magnetic coupling between the core and the shell, resulting in a large increase of the remanence and, as a result, of the energy product BHmax , a figure of merit for the quality of permanent magnets (for more than twice compared to the core alone).
COBISS.SI-ID: 28332071
Secondary re-crystallization is one of the most important processes in hydrothermal synthesis. In this process individual nanoparticles rapidly grow at the expense of the other particles. The process makes the control of the particle size very difficult. In the article, the new procedure was published. The procedure is based on the complete blocking of the secondary re-crystallization using the addition of oleic acid. The synthesized nanoparticles were hydrophobic and can be dispersed in nonpolar carrier liquids to prepare hexaferrite-based ferrofluids for the first time.
COBISS.SI-ID: 22768167
The size of nanoparticles is usually controlled with synthesis conditions and/or with the addition of surfactants. However, the synthesis of the exactly optimal particles with nano size showing, at the same time, applicable physical properties, still remains a challenge for many compounds. In this contribution we represent an alternative route for the particle-size control that is based on partial substitution of iron ions with the larger ions of scandium or indium. We showed that such substitutions, using hydrothermal synthesis, affects the nucleation rate and prevents secondary recrystallization of particles. Namely, the later results in exaggerated particle growth of barium ferrite. This procedure enables synthesis of nanoplates with diameters of 50-100 nm and thicknesses of 3-5 nm, which show applicable magnetic properties.
COBISS.SI-ID: 26308391