National Institute Of Materials Physics - Romania

The effects of severe plastic deformation (SPD) process via high-speed high-pressure torsion technique on martensitic transformation of Ni-Fe-Ga Heusler shape memory alloy are the subject of this work. The results show that moderate degrees of deformation lead to a decrease in the martensitic transformation temperatures, while the heat of reaction is enhanced only for the sample processed with the lowest degree of deformation. The results are explained by the interplay between the constituent tetragonal L10 and the cubic gamma crystal structures and the evolution of the samples morphology with the severity of deformation. The reduction in the samples granulation due to the progressive increase in the SPD is reflected by the magnetic properties of the samples with decreasing coercivity and Curie temperatures. At the highest applied degree of deformation, sample nanostructuring and a possible amorphization might explain the vanishing of MT.

The 20S proteasome enzyme complex is involved in the proteolytic degradation of misfolded and oxidatively damaged proteins and is a focus of medical research for the development of compounds with pharmaceutical properties, which are active in cancer cells and/or neurodegenerative diseases. The present study aims to develop a biosensor for investigating the 20S proteasome activity and inhibition by means of electrochemical methods. The 20S proteasome is best immobilized at the electrode surface through bio-affinity interactions with antibodies that target different subunits on the 20S proteasome, enabling the investigation of the effect of an enzyme's orientation on biosensor response. The enzymatic activity is analyzed by fixed potential amperometry with the highest sensitivity of 24 mu A cm(-2) mM(-1) and a LOD of 0.4 mu M. The detection principle involves the oxidation of an electroactive probe that is released from the enzyme's substrates upon proteolysis. The most sensitive biosensor is then used to study the multicatalytic activity of the 20S proteasome, i.e. the caspase-, trypsin- and chymotrypsin-like activity, by analyzing the biosensor's sensitivity towards different substrates. The behavior of the immobilized 20S proteasome is investigated as a function of substrate concentration. The kinetic parameters are derived and compared with those obtained when the enzyme was free in solution, with K-0.5 values being one to two orders of magnitude lower in the present case. Two 20S inhibitors, epoxomicin and bortezomib, are investigated by analyzing their influence on the 20S biosensor response. The proposed analytical method for proteasome activity and inhibitor screening has the main advantage of being cost-effective compared to the ones typically employed.

Herein, the properties of the organic heterostructures with triple-layer ZnO/Ag/ZnO as a replacement for ITO and mixed layer containing arylenevinylene oligomer (based on triphenylamine or carbazole) donor and nonfullerene (perylene diimide) acceptor mixed in the ratio 1:2 and the effect of a buffer layer of PEDOT-PSS intercalated between triple layer and mixed organic layer are discussed. The UV-vis transmission and photoluminescence (PL) properties are investigated in correlation with the surface topography and reveal a good match between the absorption and emission domain, which can favor the generation of the charge carriers. The heterostructure with the mixed layer based on triphenylamine oligomer shows the widest absorption domain, and the PL spectra of the heterostructures realized with either triphenylamine or carbazole oligomer show peaks corresponding to the radiative decay of the donor and acceptor. The I-V characteristics in the dark indicate a slightly nonlinear behavior and the current is affected by the charge carriers recombination on the defects present in the thick mixed layer deposited by matrix-assisted pulsed laser evaporation. The effect of the PEDOT-PSS buffer layer on the electrical properties of the organic heterostructure with ZnO/Ag/ZnO electrode is also investigated.

Green chemistry principles were used to phytosynthesis of three types of silver nanoparticles (AgNPs) from aqueous extracts of: nettle (Urtica dioica) leaves, black grapes (Vitis vinifera fruits), and their mixture. The combination of these extracts proved to be the most potent bioreductant for Ag+, as compared to each extract alone. UV-Vis absorption and FT-IR spectroscopy proved the formation of silver nanoparticles. Total polyphenols' quantification of vegetal extracts and "green" AgNPs was carried out by Folin-Ciocalteu analysis. Structural (XRD) analysis revealed crystalline nature of bio-developed AgNPs. Morphological studies (AFM) showed spherical shape and the nano-scale dimensions of the obtained metallic nanoparticles. Physical stability of "green" developed nanoparticles was estimated by zeta potential measurements, and their biological activity was checked by evaluating the antimicrobial and the antioxidant potency. AgNPs phyto-generated from a combination of two extracts (nettle and grapes) proved to be the most bio-active, combining in a synergistic manner, the properties of nettle and grapes. These nanoparticles exhibited high antioxidant activity (AA = 89.4%) evaluated through chemiluminescence method, and strong antibacterial effect (showing an inhibition zone diameter of 20 mm) against Escherichia coli.

Almost six decades ago, in Romania a small group of physicists begun to study chalcogenide compositions, motivated primarily by the desire to understand the phase-change phenomenon in these materials, discovered recently, at that time, by Stanford R. Ovshinsky. It took not too long for them to realize the challenges these materials set to the research. With newcomers to the field, the research was broadened. In some cases just for basic research, to model, and to understand the chalcogenide materials, whereas in other cases, the applicative potential was revealed and used. Herein, the evolution of the field of these somewhat exotic materials is followed, listing the main contributions done in Romania, both in basic and applied research.

Y2O3:Yb(3+)5 at% ceramics have been synthesized by the reactive sintering method using different commercial yttria powders (Alfa-Micro, Alfa-Nano, and ITO-V) as raw materials. It has been shown that all Y(2)O(3)starting powders consist from agglomerates up to 5-7 mu m in size which are formed from 25-60 nm primary particles. High-energy ball milling allows to significantly decreasing the median particle sizeD(50)below 500 nm regardless of the commercial powders used. Sintering experiments indicate that powder mixtures fabricated from Alfa-Nano yttria powders have the highest sintering activity, while (Y0.86La0.09Yb0.05)(2)O(3)ceramics sintered at 1750 degrees C for 10 h are characterized by the highest transmittance of about 45%. Y2O3:Yb(3+)ceramics have been obtained by the reactive sintering at 1750-1825 degrees C using Alfa-Nano Y(2)O(3)powders and La2O3+ZrO(2)as a complex sintering aid. The effects of the sintering temperature on densification processes, microstructure, and optical properties of Y2O3:Yb(3)(+)5 at% ceramics have been studied. It has been shown that Zr(4)(+)ions decrease the grain growth of Y2O3:Yb(3+)ceramics for sintering temperatures 1750-1775 degrees C. Further increasing the sintering temperature was accompanied by a sharp increase of the average grain size of ceramics referred to changes of structure and chemical composition of grain boundaries, as well as their mobility. It has been determined that the optimal sintering temperature to produce high-dense yttria ceramics with transmittance of 79%-83% and average grain size of 8 mu m is 1800 degrees C. Finally, laser emission at similar to 1030.7 nm with a slope efficiency of 10% was obtained with the most transparent Y2O3:Yb(3+)5 at% ceramics sintered.

This study addresses the deposition with improved adhesion of TiO2:N/SiO(2)mixture, with different concentrations of the nano-powders (NPs) (1:0,5; 1:1 and 1:1,5) on 100% cotton fabrics. The characteristics of the deposited thin films were investigated by scanning electron microscopy (SEM), Rutherford backscattering spectrometry (RBS), Raman scattering, FTIR, and UV-VIS absorption spectroscopy. To improve the treatment durability to the external factors, the different crosslinking methods were used. Photocatalytic activity of functionalized textile fabrics was evaluated by determining the photodegradation efficiency of the methylene blue (MB) dye and forest juice, measuring the color difference of the irradiated samples compared with non-irradiated samples. Washing durability of the samples was achieved qualitatively by determining the photocatalytic activity remaining on the textile fabrics after 1 and 5 washing cycles. The samples treated with the mixture of TiO2:N/SiO(2)have demonstrated improved self-cleaning properties, the highest photocatalytic activity being obtained for the highest value of TiO2:N/SiO(2)NPs molar concentrations equal to 1:1.

To enhance the spectral response of solar cells, an experimental study on LaPO4:0.01Ce(3+)/xNd(3+) (x = 0, 2, 4 mol%) was carried out, where structural and morphological properties of the prepared samples were well characterized by the means of X-ray diffraction, Fourier transform infrared spectroscopy, and scanning electronic microscope. Additionally, the photoluminescence behavior of phosphors in ultraviolet-visible (UV-VIS) and Near-infrared (NIR) regions were investigated to confirm the energy transfer (ET) from Ce3+ to Nd3+. Moreover, the quantum efficiency of Ce3+/Nd3+-co-doped samples was estimated as high as similar to 172% and the possible ET process was described. Accordingly, the LaPO4:Ce3+/Nd3+ phosphors can convert the UV light (275 nm) into NIR photons (approx. 1059 nm) through the possible two-pathway energy transfer processes from Ce3+ sensitizer ions to Nd3+ activators. Obtained NIR down-conversion emissions are suitable for improving the conversion efficiency of c-Si solar cells.