Influence of Hafnium Addition on the Microstructure, Microhardness and Corrosion Resistance of Ti20Ta20Nb20(ZrMo)20-xHfx (where x = 0, 5, 10, 15 and 20 at.%) High Entropy Alloys.

The presented work aimed to investigate the influence of the hafnium/(zirconium and molybdenum) ratio on the microstructure, microhardness and corrosion resistance of Ti20Ta20Nb20(ZrMo)20-xHfx (where x = 0, 5, 10, 15 and 20 at.%) high entropy alloys in an as-cast state produced from elemental powder and obtained via the vacuum arc melting technique. All studied alloys contained only biocompatible elements and were chosen based on the thermodynamical calculations of phase formation predictions after solidification. Thermodynamical calculations predicted the presence of multi-phase, body-centered cubic phases, which were confirmed using X-ray diffraction and scanning electron microscopy. Segregation of alloying elements was recorded using elemental distribution maps. A decrease in microhardness with an increase in hafnium content in the studied alloys was revealed (512-482 HV1). The electrochemical measurements showed that the studied alloys exhibited a high corrosion resistance in a simulated body fluid environment (breakdown potential 4.60-5.50 V vs. SCE).

Interfacial Polarization Phenomena in Compressed Nanowires of SbSI.

The systematic studies of the extrinsic Maxwell-Wagner-Sillars polarization process in compressed antimony sulfoiodide (SbSI) nanowires are carried out by dielectric spectroscopy. The dielectric response is studied in temperature (100≤T≤350) K and frequency (10-3≤f≤106) Hz ranges. Dielectric functions commonly used for the analysis of dielectric spectra related to intrinsic polarization processes were applied in the elaboration of experimental data. It was found that the respective "semi-circles" in the Cole-Cole-type plots display a characteristic pear-like shape for the ferroelectric phase. On the other hand, the data for the paraelectric phase form symmetrical arcs. This response is effectively parametrized using the experimental Cole-Davidson and Cole-Cole functions fitted to the data obtained for the ferroelectric and paraelectric phases, respectively. It is deduced that the particular shape of spectra in the ferroelectric phase is due to spontaneous polarization, which is responsible for an asymmetric broadening of relaxation functions related to the interfacial polarization.

Influence of Molybdenum on the Microstructure, Mechanical Properties and Corrosion Resistance of Ti20Ta20Nb20(ZrHf)20-xMox (Where: x = 0, 5, 10, 15, 20) High Entropy Alloys.

The presented work was focused on investigating the influence of the (hafnium and zirconium)/molybdenum ratio on the microstructure and properties of Ti20Ta20Nb20(ZrHf)20-xMox (where: x = 0, 5, 10, 15, 20 at.%) high entropy alloys in an as-cast state. The designed chemical composition was chosen due to possible future biomedical applications. Materials were obtained from elemental powders by vacuum arc melting technique. Phase analysis revealed the presence of dual body-centered cubic phases. X-ray diffraction showed the decrease of lattice parameters of both phases with increasing molybdenum concentration up to 10% of molybdenum and further increase of lattice parameters. The presence of two-phase matrix microstructure and hafnium and zirconium precipitates was proved by scanning and transmission electron microscopy observation. Mechanical property measurements revealed decreased micro- and nanohardness and reduced Young's modulus up to 10% of Mo content, and further increased up to 20% of molybdenum addition. Additionally, corrosion resistance measurements in Ringers' solution confirmed the high biomedical ability of studied alloys due to the presence of stable oxide layers.

Fast and Efficient Piezo/Photocatalytic Removal of Methyl Orange Using SbSI Nanowires.

Piezocatalysis is a novel method that can be applied for degradation of organic pollutants in wastewater. In this paper, ferroelectric nanowires of antimony sulfoiodide (SbSI) have been fabricated using a sonochemical method. Methyl orange (MO) was chosen as a typical pollutant, as it is widely used as a dye in industry. An aqueous solution of MO at a concentration of 30 mg/L containing SbSI nanowires (6 g/L) was subjected to ultrasonic vibration. High degradation efficiency of 99.5% was achieved after an extremely short period of ultrasonic irradiation (40 s). The large reaction rate constant of 0.126(8) s-1 was determined for piezocatalytic MO decomposition. This rate constant is two orders of magnitude larger than values of reaction rate constants reported in the literature for the most efficient piezocatalysts. These promising experimental results have proved a great potential of SbSI nanowires for their application in environmental purification and renewable energy conversion.

A Ferroelectric-Photovoltaic Effect in SbSI Nanowires.

A ferroelectric-photovoltaic effect in nanowires of antimony sulfoiodide (SbSI) is presented for the first time. Sonochemically prepared SbSI nanowires have been characterized using high-resolution transmission electron microscopy (HRTEM) and optical diffuse reflection spectroscopy (DRS). The temperature dependences of electrical properties of the fabricated SbSI nanowires have been investigated too. The indirect forbidden energy gap EgIf = 1.862 (1) eV and Curie temperature TC = 291 (2) K of SbSI nanowires have been determined. Aligned SbSI nanowires have been deposited in an electric field between Pt electrodes on alumina substrate. The photoelectrical response of such a prepared ferroelectric-photovoltaic (FE-PV) device can be switched using a poling electric field and depends on light intensity. The photovoltage, generated under λ = 488 nm illumination of Popt = 127 mW/cm² optical power density, has reached UOC = 0.119 (2) V. The presented SbSI FE-PV device is promising for solar energy harvesting as well as for application in non-volatile memories based on the photovoltaic effect.

Effect of Nanoparticles Surface Charge on the Arabidopsis thaliana (L.) Roots Development and Their Movement into the Root Cells and Protoplasts.

Increasing usage of gold nanoparticles (AuNPs) in different industrial areas inevitably leads to their release into the environment. Thus, living organisms, including plants, may be exposed to a direct contact with nanoparticles (NPs). Despite the growing amount of research on this topic, our knowledge about NPs uptake by plants and their influence on different developmental processes is still insufficient. The first physical barrier for NPs penetration to the plant body is a cell wall which protects cytoplasm from external factors and environmental stresses. The absence of a cell wall may facilitate the internalization of various particles including NPs. Our studies have shown that AuNPs, independently of their surface charge, did not cross the cell wall of Arabidopsis thaliana (L.) roots. However, the research carried out with using light and transmission electron microscope revealed that AuNPs with different surface charge caused diverse changes in the root's histology and ultrastructure. Therefore, we verified whether this is only the wall which protects cells against particles penetration and for this purpose we used protoplasts culture. It has been shown that plasma membrane (PM) is not a barrier for positively charged (+) AuNPs and negatively charged (-) AuNPs, which passage to the cell.

The development of a hairless phenotype in barley roots treated with gold nanoparticles is accompanied by changes in the symplasmic communication.

Uptake of water and nutrients by roots affects the ontogenesis of the whole plant. Nanoparticles, e.g. gold nanoparticles, have a broad range of applications in many fields which leads to the transfer of these materials into the environment. Thus, the understanding of their impact on the growth and development of the root system is an emerging issue. During our studies on the effect of positively charged gold nanoparticles on the barley roots, a hairless phenotype was found. We investigated whether this phenotype correlates with changes in symplasmic communication, which is an important factor that regulates, among others, differentiation of the rhizodermis into hair and non-hair cells. The results showed no restriction in symplasmic communication in the treated roots, in contrast to the control roots, in which the trichoblasts and atrichoblasts were symplasmically isolated during their differentiation. Moreover, differences concerning the root morphology, histology, ultrastructure and the cell wall composition were detected between the control and the treated roots. These findings suggest that the harmful effect of nanoparticles on plant growth may, among others, consist in disrupting the symplasmic communication/isolation, which leads to the development of a hairless root phenotype, thus limiting the functioning of the roots.

Unique chromoplast organisation and carotenoid gene expression in carotenoid-rich carrot callus.

MAIN CONCLUSION: The new model orange callus line, similar to carrot root, was rich in carotenoids due to altered expression of some carotenogenesis-associated genes and possessed unique diversity of chromoplast ultrastructure. Callus induced from carrot root segments cultured in vitro is usually pale yellow (p-y) and poor in carotenoids. A unique, non-engineered callus line of dark orange (d-o) colour was developed in this work. The content of carotenoid pigments in d-o callus was at the same level as in an orange carrot storage root and nine-fold higher than in p-y callus. Carotenoids accumulated mainly in abundant crystalline chromoplasts that are also common in carrot root but not in p-y callus. Using transmission electron microscopy, other types of chromoplasts were also found in d-o callus, including membranous chromoplasts rarely identified in plants and not observed in carrot root until now. At the transcriptional level, most carotenogenesis-associated genes were upregulated in d-o callus in comparison to p-y callus, but their expression was downregulated or unchanged when compared to root tissue. Two pathway steps were critical and could explain the massive carotenoid accumulation in this tissue. The geranylgeranyl diphosphate synthase gene involved in the biosynthesis of carotenoid precursors was highly expressed, while the ß-carotene hydroxylase gene involved in ß-carotene conversion to downstream xanthophylls was highly repressed. Additionally, paralogues of these genes and phytoene synthase were differentially expressed, indicating their tissue-specific roles in carotenoid biosynthesis and metabolism. The established system may serve as a novel model for elucidating plastid biogenesis that coincides with carotenogenesis.

Ferroelectric SbSI nanowires for ammonia detection at a low temperature.

For the first-time, an ammonia (NH3) gas sensor has been fabricated using antimony sulfoiodide (SbSI). A few aligned SbSI nanowires have been bonded to Au microelectrodes on a glass substrate. The fabricated sensor has been tested for various concentrations of NH3 in N2 at operating temperatures below (T = 280 K) and above (T = 304 K) Curie point of SbSI. A significantly higher response and sensitivity of the sensor is observed, when the operating temperature is lower than Curie temperature. However, comparable values of the low detection limits (6.0 ±â€¯2.4) ppm and (6.3 ±â€¯3.9) ppm have been determined at operating temperatures of 280 K and 304 K, respectively. The current response, as well as the sensitivity versus ammonia concentration, follow the power laws known for conductometric gas sensors. SbSI nanosensor exhibits good stability, short term response reversibility, and does not require a heating system for recovery. This device also demonstrates a high selectivity to NH3 against other interfering gases. The ammonia sensing mechanism has been explained by considering the formation of NH4+ ions on the nanowire surface and the occurrence of proton transfer according to Grotthuss's chain reaction.

Fate of neutral-charged gold nanoparticles in the roots of the Hordeum vulgare L. cultivar Karat.

Nanoparticles (NPs) have a significant impact on the environment and living organisms. The influence of NPs on plants is intensively studied and most of the data indicate that NPs can penetrate into plants. The studies presented here were performed on the roots of Hordeum vulgare L. seedlings using neutral-charge gold nanoparticles (AuNPs) of different sizes. In contrast to the majority of the published data, the results presented here showed that during the culture period, AuNPs: 1/did not enter the root regardless of their size and concentration, 2/that are applied directly into the cells of a root do not move into neighbouring cells. The results that were obtained indicate that in order to extend our knowledge about the mechanisms of the interactions between NPs and plants, further studies including, among others, on different species and a variety of growth conditions are needed.

Ferroelectric properties of ultrasonochemically prepared SbSI ethanogel.

This article presents for the first time the electrical properties of sonochemically synthesised, high-surface-area SbSI ethanogel made up of large quantity nanowires with lateral dimensions of about 10-50 nm and lengths reaching up to several micrometers. The composition, morphology, dimensions, microstructures, and optical energy gap of the new form of SbSI were characterized. This material is a semiconducting ferroelectric as in the case of bulk SbSI crystals. The maximum of dielectric constant epsilon=1.6x10(4) is observed at Tc=292(1) K. The activation energies in temperature dependences of electric conductivity of SbSI ethanogel are different for ferroelectric and paraelectric phases during heating and cooling of the sample.