Anna Elsukova

Splenic red pulp macrophages are intrinsically superparamagnetic and contaminate magnetic cell isolates

A main function of splenic red pulp macrophages is the degradation of damaged or aged erythrocytes. Here we show that these macrophages accumulate ferrimagnetic iron oxides that render them intrinsically superparamagnetic. Consequently, these cells routinely contaminate splenic cell isolates obtained with the use of MCS, a technique that has been widely used in immunological research for decades. These contaminations can profoundly alter experimental results. In mice deficient for the transcription factor SpiC, which lack red pulp macrophages, liver Kupffer cells take over the task of erythrocyte degradation and become superparamagnetic. We describe a simple additional magnetic separation step that avoids this problem and substantially improves purity of magnetic cell isolates from the spleen.

Low-temperature synthesis of crystalline BaTiO3 nanoparticles by one-step “organosol”-precipitation

The “organosol” precipitation method is proposed to produce nanosized particles of barium titanate (BaTiO3) at temperatures as low as room temperature. The advantages of this method are a high yield, a simple but precise control of the size of the particles, low process temperature, short reaction time, as well as low cost of reagents. The particles were systematically characterized by powder X-ray diffraction (XRD), Raman scattering, scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), thermogravimetric thermal analysis (TGA/DSC), infrared spectroscopy (IR), and impedance analysis. The as-prepared BaTiO3 nanocrystals exhibit a granular shape of around 15 nm in diameter. Oleic acid retards crystallization and thus allows generation of a uniformly small grain size and excellent dispersibility in organic solvents. The surface energy of the particles is modified and crystallization in cubes also arises. The mechanism of powder formation is discussed. The method offers an alternate low-cost route to perovskite nanopowders easily dispersed in organic media.

Cobalt Ferrite/Barium Titanate Core/Shell Nanoparticles

Cobalt ferrite/barium titanate nanoparticles with a core/shell structure were synthesized by combining co-precipitation and organosol methods. The average particle size was about 110 nm with an average shell thickness of about 40 nm. Dielectric and magnetic properties of the particles were studied using impedance and Mössbauer spectroscopy, respectively. The particles are promising for fabrication of multiferroic ceramics with the core-shell structure.

Diffusion Enhancement in FePt Nanoparticles for L1\(_0\) Stability

FePt has a high magnetic anisotropy in the thermodynamically stable L1\(_0\) phase, so that nanoparticles of this material could remain ferromagnetic at small sizes and be used for magnetic storage. However, the stabilization of the L1\(_0\) phase is not straight forward at small particle sizes, and instead, twinned icosahedral structures are formed which are thought to be metastable. In order to enhance the formation of the L1\(_0\) phase, the lattice has to be agitated so that icosahedral structures will destabilize. In addition to thermal annealing‚ we introduce agitation methods related to oxygen reactive sputtering, nitriding-denitriding, and segregation in FePt nanoparticles prepared in the gas phase. We discuss principally the structural properties of the particles obtained prior to and after employing the various agitation techniques.