We report the synthesis and characterization of amorphous iron oxide nanoparticles from iron salts in aqueous extracts of monocotyledonous (Hordeum vulgare) and dicotyledonous (Rumex acetosa) plants. The nanoparticles were characterized by TEM, absorbance spectroscopy, SAED, EELS, XPS, and DLS methods and were shown to contain mainly iron oxide and iron oxohydroxide. H. vulgare extracts produced amorphous iron oxide nanoparticles with diameters of up to 30 nm. These iron nanoparticles are intrinsically unstable and prone to aggregation; however, we rendered them stable in the long term by addition of 40 mM citrate buffer pH 3.0. In contrast, amorphous iron oxide nanoparticles (diameters of 10-40 nm) produced using R. acetosa extracts are highly stable. The total protein content and antioxidant capacity are similar for both extracts, but pH values differ (H. vulgare pH 5.8 vs R. acetosa pH 3.7). We suggest that the presence of organic acids (such oxalic or citric acids) plays an important role in the stabilization of iron nanoparticles, and that plants containing such constituents may be more efficacious for the green synthesis of iron nanoparticles.

The process of open-porous structure development in highdensity polyethylene (HDPE) films during uniaxial deformation in supercritical carbon dioxide (SC-CO 2 ) fluid at 35 °C and 10 MPa has been studied and visualized by means of atomic force microscopy. We suggest that the supercritical fluid act as adsorption-active medium, and the porous structure is developed via the crazing mechanism due to the increasing the distance between of lamellae and the formation of oriented separate fibrils in the intercrystallite space. Effective bulk porosity of the films has been up to 40%. Small-angle X-ray scattering studies and ethanol permeability measurements have revealed that the pores and fibrils are about 10 nm in diameter. The prepared nanoporous materials exhibit good vapor permeability. Structural and mechanical behavior of the prepared porous films has been investigated. Large reversible deformation (up to 80%) of HDPE in the SC-CO 2 has been observed. Repeated drawing of the shrunk films in air under ambient conditions has led to the open-porous structure recovery.

It is shown that the impedance spectroscopy allows identification of the resistive switching mechanisms in complex composite structures. This statement was demonstrated on an example of organic based sandwich structures with a modified polymer matrix as an active element. The impedance spectroscopy scanning was performed for a series of intermediate states formed within the switching process. Analysis of the experimentally obtained impedance spectra shows that the electron transport is provided by delocalized charge carriers and proceeds via conducting filaments formed in a highly resistive matrix. The filament configuration changes during the switching. With the shift from isolating to conducting states, single isolated filaments are reorganized into a branched network.

We report on the influence of oxidation on features of surface electron states in PbSe films-materials belonging to the family of topological crystalline insulators Pb Sn Se. These states are detected through observation of the photoelectromagnetic effect induced by terahertz laser pulses. It is demonstrated that highly conductive surface electron states in PbSe are inherent to the semiconductor itself and are not related to the material oxidation. This allows excluding surface states induced by oxidation as a reason for high surface conductivity in topological crystalline insulators based on Pb Sn Se.Index Terms-IV-VI semiconductor materials, photoelectromagnetic effect, surface conductivity, terahertz, topological insulators (TIs). and also with the P.N. Lebedev Physical Institute,

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ПОРТАТИВНАЯ ЯЧЕЙКА ДЛЯ КАЧЕСТВЕННОЙ ОЦЕНКИ ПАРОПРОНИЦАЕМОСТИ ПЛЕНОЧНЫХ МАТЕРИАЛОВ

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