Martin Fabián

Mechanosynthesis of nanocrystalline fayalite, Fe2SiO4

Nanostructured fayalite (α-Fe(2)SiO(4)) with a large volume fraction of interfaces is synthesized for the first time via single-step mechanosynthesis, starting from a 2α-Fe(2)O(3) + 2Fe + 3SiO(2) mixture. The nonequilibrium state of the as-prepared silicate is characterized by the presence of deformed polyhedra in the interface/surface regions of nanoparticles.

Characterization of mechanochemically synthesized lead selenide

Mechanochemical synthesis of lead selenide PbSe nanocrystals was performed by high-energy milling of lead and selenium powders in a planetary ball mill. The structure properties of synthesized lead selenide were characterized by XRD analysis that confirmed crystalline nature of PbSe nanocrystals. Calculated average size of PbSe crystallites was 37 nm. The methods of particle size distribution analysis, specific surface area measurement, SEM and TEM were used for the characterization of surface and morphology of PbSe nanocrystals. SEM analysis revealed agglomerates of PbSe particles. However, HRTEM analysis confirmed perfect stoichiometric PbSe cubes with NaCl structure as well. UV-VIS-NIR spectrophotometry was used to confirm the blue shift of the small particles occurring in the powder product obtained by the mechanochemical synthesis.

PbS nanostructures synthesized via surfactant assisted mechanochemical route

PbS nanocrystals using surfactant assisted mechanochemical route has been successfully prepared. The methods of XRD, SEM, surface area and particle size measurements were used for nanocrystals characterization. The XRD patterns confirmed the presence of galena PbS (JCPDS 5–592) whatever treatment conditions were applied. The strong observable peaks indicate the highly crystalline nature in formation of PbS nanostructures where preferential crystal growth in the (200) direction after chelating agent (EDTANa2•2H2O) addition has been observed. The mean volume weighted crystallite size 4.9 nm and 35 nm has been calculated from XRD data using Williamson-Hall method for PbS synthesized without and/or with chelating agent, respectively corresponding with surface weighted crystallites sizes of 2.9 and 18.8 nm. The sample prepared without surfactant yields the smaller crystallites and the higher microstrain compared with surfactant assisted synthesis. The obtained results illustrate a possibility to manipulate crystal morphology by combining effect of milling and surfactant application.

A simple and straightforward mechanochemical synthesis of the far-from-equilibrium zinc aluminate, ZnAl2O4, and its response to thermal treatment

Zinc aluminate (ZnAl2O4) nanoparticles with an average size of about 10 nm are synthesized via one-step mechanochemical processing of the ZnO : γ-Al2O3 stoichiometric mixture at ambient temperature. The mechanochemically induced formation of the phase is followed by XRD and 27Al MAS NMR. High-resolution TEM studies reveal a non-uniform nanostructure of mechanosynthesized aluminate consisting of ordered grains surrounded or separated by disordered surface and interfacial regions. Due to the capability of 27Al MAS NMR to probe the local environment of the Al cations, valuable insights into the short-range structure of ZnAl2O4 on the Angstrom length scale are provided. It is demonstrated that the as-prepared aluminate possesses a partly inverse spinel structure with a far-from equilibrium arrangement of cations and distorted polyhedra, which are spatially confined to the surface and interfacial regions with a volume fraction of ca. 50% and a thickness of ca. 1 nm. The response of the nanostructured ZnAl2O4 to subsequent thermal treatment is further investigated. It turned out that the thermally induced grain growth is accompanied by a release of microstrain, by a shrinkage of the lattice parameter, as well as by a variation in the oxygen parameter and metal–oxygen bond lengths. Evidence is given of the thermally induced redistribution of cations approaching their equilibrium positions. Upon heating above 1100 K, mechanosynthesized ZnAl2O4 relaxes towards a structural state that is similar to the bulk one.

Magnetic Fluids Have Ability to Decrease Amyloid Aggregation Associated with Amyloid‐Related Diseases

At least twenty human proteins can fold abnormally to form pathological deposits that are associated with several amyloid‐related diseases. We have investigated the effect of four magnetic fluids (MFs)—electrostatically stabilized Fe3O4 magnetic nanoparticles (MF1) and sterically stabilized Fe3O4 magnetic nanoparticles by sodium oleate (MF2, MF3 and MF4) with adsorbed BSA (MF2) or dextran (MF4)—on amyloid aggregation of two proteins, human insulin and chicken egg lysozyme. The morphology, particle size and size distribution of the prepared magnetic fluids were characterized. We have found that MFs are able to decrease amyloid aggregation of both studied proteins and the extent of depolymerization depended on the MF properties. The most effective reduction was observed for MF4 as 90% decrease of amyloids was detected for insulin and lysozyme amyloid aggregates. Our findings indicate that MFs have potential to be used for treatment of amyloid diseases.

Structural characterization of (Bi1-xGdx)14W2O27 (x = 0.00 and 0.05) synthesized via mechano-thermal treatment

ABSTRACT Samples of (Bi1-xGdx)14W2O27 (x = 0 and 0.05) compounds were prepared via a combination of mechanochemical and thermal treatments upon a Bi2O3/WO3/Gd2O3 stoichiometric mixture of precursors. Phase evolution, as well as the determination of structural parameters in as-prepared compounds, were performed by XRD analysis. Rietveld refinement revealed that gadolinium ions are incorporated into the tetragonal structure of Bi14W2O27 with preference to occupy octahedrally coordinated Bi3+ sites. The Gd doping induced an increase in Bi sites coordination, i.e., the number of oxygens around Bi/Gd ions increased, which can be explained by the absence of 6s2 lone pair electrons in gadolinium ions.