Development of nanotechnology leads to the increasing release of nanoparticles in the environment that results in accumulation of different NPs in living organisms including plants. This can lead to serious changes in plant cultures which leads to genotoxicity. The aims of the present study were to detect if iron oxide NPs pass through the flax cell wall, to compare callus morphology, and to estimate the genotoxicity in Linum usitatissimum L. callus cultures induced by different concentrations of Fe 3 O 4 nanoparticles. Two parallel experiments were performed: experiment A, where flax explants were grown on medium supplemented with 0.5 mg/l, 1 mg/l, and 1.5 mg/l Fe 3 O 4 NPs for callus culture obtaining, and experiment B, where calluses obtained from basal MS medium were transported into medium supplemented with concentrations of NPs identical to experiment A. Obtained results demonstrate similarly in both experiments that 25 nm Fe 3 O 4 NPs pass into callus cells and induce low toxicity level in the callus cultures. Nevertheless, calluses from experiment A showed 100% embryogenesis in comparison with experiment B where 100% rhizogenesis was noticed. It could be associated with different stress levels and adaptation time for explants and calluses that were transported into medium with Fe 3 O 4 NPs supplementation.
Thin films of rhenium trioxide (ReO 3) were produced by reactive DC magnetron sputtering from metallic rhenium target followed by annealing in the air in the range of temperatures from 200C to 350C. Nanocrystalline singlephase ReO 3 films were obtained upon annealing at about 250C. The thin films appear bright red in reflected light and blue-green in transmitted light, thus showing an optical transparency window in the spectral range of 475-525 nm. The film exhibits high conductivity, evidenced by macro-and nano-scale conductivity measurements. The longrange and local atomic structures of the films were studied in detail by structural methods as X-ray diffraction and X-ray absorption spectroscopy. The oxidation state (6+) of rhenium was confirmed by X-ray photoemission and Xray absorption spectroscopies. The nanocrystalline morphology of the annealed films was evidenced by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and atomic force microscopy (AFM). The obtained results allowed us to propose the mechanism of rhenium oxide conversion from the initially amorphous ReO x phase to cubic ReO 3. 1. Introduction Rhenium oxides are known to exist in the three main phases ReO 2 , ReO 3 and Re 2 O 7 , corresponding to the oxidation states of Re 4+ , Re 6+ and Re 7+ , respectively. ReO 2 is dark blue or black solid and has a monoclinic phase α-ReO 2 below 300°C [1]. When heated above 300°C, it irreversibly turns into the orthorhombic phase β-ReO 2 , which is stable in vacuum to 850-1000°C but oxidizes in the air to Re 2 O 7 above 400°C. Both phases of ReO 2 have metallic conductivity [2]. Crystalline Re 2 O 7 is an inorganic polymer and it is electrically insulating material [2]. It consists of ReO 6 octahedra and ReO 4 tetrahedra. In each octahedral ReO 6 group, three of the Re-O bonds are longer than the others, and if weak bonds are broken (e.g., upon heating) volatile molecules of Re 2 O 7 are produced. Re 2 O 7 sublimes at temperatures above 360°C. Besides, Re 2 O 7 is highly hygroscopic, decomposing into perrhenic acid (HReO 4) when exposed to moisture [3]. ReO 3 is a red solid with a metallic luster. Its cubic crystalline structure is of perovskite-type and is formed by a network of regular ReO 6 octahedra, which have common vertices in three
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