National Institute Of Materials Physics - Romania

We report results regarding the in vitro toxicology of gamma-Bi2O3 represented by its isomorphous phase Bi12TiO20 (gamma-BTO). The gamma-BTO microparticles were synthesized by two methods: coprecipitation from a bismuth nitrate tetrabutyl titanate solution and solid state reaction of Bi2O3 and TiO2 oxides. The structural and morphological characteristics of the obtained materials were determined using X-ray diffraction (XRD), selected area electron diffraction (SAED), transmission (TEM) and scanning (SEM) electron microscopy. The elemental composition was investigated using energy dispersive spectrometry (EDS). The cytotoxicity and oxidative/nitrosative stress (intracellular reactive oxygen species (ROS) and nitric oxide (NO) release) induced by the studied microparticles in HepG2, SH-SY5Y and 3T3-L1 cell cultures were determined using the MIT, DCF-DA (2 ',7 '-dichlorfluorescein-diacetate) and Griess methods respectively. Depending on the cell type and gamma-BTO concentration, results showed only weak cytotoxic effects after 24 h of gamma-BTO exposure and cell proliferation effects for longer treatment times. Only reduced NO release increases (corresponding to high gamma-BTO concentrations) were detected in case of SH-SY5Y and 3T3-L1 cells. The intracellular ROS production (higher for HepG2 cells) appeared inversely proportional to the gamma-BTO concentration. The obtained results indicated a promising in vitro biocompatibility of gamma-BTO and encourage further studies regarding its potential for biomedical applications. (C) 2014 Elsevier Ltd. All rights reserved.

The analysis of the sequence of electron paramagnetic resonance (EPR) spectra of trace amounts of substitutional probing paramagnetic ions incorporated in (nano)crystalline samples submitted to isothermal and isochronal pulse annealing treatments can offer a wealth of information on the thermally induced compositional and structural changes of the host material. The potential of this new thermal analysis method is illustrated here with results of such investigations on the thermal decomposition of crystalline zinc hydroxide (Zn(OH)(2)) and anhydrous zinc carbonate basic (Zn-5(CO3)(2)(OH)(6)) precursors containing trace amounts of substitutional Mn2+ probing ions into nanostructured zinc oxide-ZnO. The quantitative analysis of the sequence of isochronal pulse annealing EPR spectra could provide, besides the thermal decomposition curves of the two precursors, additional information about the structure of the resulting nanostructured ZnO, some of it hard to get by standard structural diffraction techniques. The analysis of both isochronal and isothermal pulse annealing EPR data was further used to investigate the crystallization mechanism of the initially formed nanostructured disordered ZnO and to quantitatively describe the further growth of the resulting ZnO nanocrystals with the increasing annealing temperature and duration.

By implanting Bi in Si, a strong strain field due to the bigger atomic mass and size of stopped Bi ions than Si lattice ones is produced, together with irradiation defects. The controlled doping of Si with Bi leads to modern applications such as quantum information processing. Here we show that the parameters of trapping centres are modified under the strain field. In the literature there are no reports on this subject. We irradiated Si wafers with Bi6+ ions of 28MeV kinetic energy, 3 degrees off [100] axis orientation. The depth distributions of stopped ions and of primary defects were simulated. The traps produced by irradiation were investigated using the thermally stimulated currents method without bias. We recorded and modelled the discharge current curves. The strain field was modelled as a permanent and temperature-independent electric field. The traps of V-2, VO/CiCs, and CiOi and other two not assigned were evidenced. We have found that all trapping levels are broadened, and all capture cross-sections are temperature dependent which we attribute to the strong strain field produced by Bi. These results are important and must be taken into account in designing and manufacturing microelectronic devices incorporating strain, including the topical spin qubit ones. Copyright (C) EPLA, 2014

In this paper, we report on the structural, optical, and electrical properties of a wide compositional range of AlxIn1-xN thin layers deposited on glass and polyethylene terephthalate substrates. AlxIn1-xN layers of controlled composition were obtained by a simple reactive magnetron co-sputtering protocol, using a single aluminium target with indium insets, by varying the Al/In target surface area ratio, and the composition of the deposition atmosphere. The relevant physical properties were investigated and discussed. It is shown that the texture of the thin films is dependent on the cation ratio, while the bowing parameters of lattice constants and band gap values are larger than those of epitaxial layers. (C) 2014 AIP Publishing LLC.

(Sn0.9-xIn0.1CuxO2-delta)-O-(I) (x = 0.02; 0.03 and 0.05 mol%) mesoarchitectures have been synthesized using an ionic surfactant (CTAB) as template for sensing applications. The procedure implies a facile, hydrothermal synthesis route in order to obtain mesoarchitectures built from nanoparticles. The sensors were obtained by screen-printing deposition onto planar Al2O3 substrates provided with interdigitated Pt electrodes on one side and a Pt heater on the back side. The assessment of the well organized porous structure, for the sensitive materials, as specific surface area and uniform pore size distributions were revealed by N-2 adsorption/desorption. The morphological and structural features of the resultant material were investigated by scanning electron microscopy (SEM), Raman spectroscopy and X-ray diffraction (XRD), while the surface chemistry was closely monitored by X-ray photoelectron spectroscopy (XPS). Thus, the incorporation of Cu1+ and In3+ into SnO2 lattice inducing the formation of oxygen vacancies combined with hydroxyl groups adsorbed on the outermost surface layer enhanced the sensitivity and selectivity of our sensing material. The sensors have been tested for NO2, CH4, CO, H2S target gases under humid air conditions very close to real working conditions. The sample with x = 0.05 mol% exhibits very attractive sensing properties for application as selective, low operating temperature (100 degrees C), low cost H2S sensor. With a deeper understanding of the underlying mechanisms and further improvement of the synthesis one can foresee promising applications in catalysis. (C) 2014 Elsevier Inc. All rights reserved.

Silver nanoparticles were obtained by picosecond laser ablation in water at 1064 nm, using focusing geometry to design the particles' size. The position of the target surface with respect to the focal point strongly influences the NPs' size: above and in the focus it is up to 20 nm and below focus <= 150 nm. Generated particles have a spherical shape. The solutions were further employed on human cells and the tests showed a deteriorating effect on DNA.

Si/SiO2 quantum dots (QDs) are novel particles with unique physicochemical properties that promote them as potential candidates for biomedical applications. Although their interaction with human cells has been poorly investigated, oxidative stress appears to be the main factor involved in the cytotoxicity of these nanoparticles. In this study, we show for the first time the influence of Si/SiO2 QDs on cellular redox homeostasis and glutathione distribution in human lung fibroblasts. The nanoparticles morphology, composition and structure have been investigated using high resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED), energy-dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD) analysis. MRC-5 cells (human lung fibroblasts) were incubated with various concentrations of Si/SiO2 QDs ranging between 25 and 200 mu g/mL for up to 72 h. The results of the MTT and sulforhodamine B assays showed that exposure to QDs led to a time-dependent decrease in cell viability and biomass. The increase in reactive oxygen species (ROS) and malondialdehyde (MDA) levels together with the lower glutathione content suggested that the cellular redox homeostasis was altered. Regarding GSH distribution, the first two days of treatment resulted in a localization of GSH mainly in the cytoplasm, while at longer incubation time the nuclear/cytoplasmic ratio indicated a nuclear localization. These modifications of cell redox state also affected the redox status of proteins, which was demonstrated by the accumulation of oxidized proteins and actin S-glutathionylation. In addition, the externalization of phosphatidylserine provided evidence that apoptosis might be responsible for cell death, but necrosis was also revealed. Our results suggest that Si/SiO2 quantum dots exerted cytotoxicity on MRC-5 cells by disturbing cellular homeostasis which had an effect upon protein redox status. (C) 2014 Elsevier Ireland Ltd. All rights reserved.

High density (above 93%) superconducting bulks of MgB2 with addition of hexagonal BN (h-BN) and cubic BN (c-BN) with compositions ((MgB2) + (BN)(x), x = 0.01, 0.03, 0.05) were obtained by ex situ spark plasma sintering. All the investigated samples have the critical temperature T-c = 38.8 K. The variation of the critical current density J(c) with the external magnetic field H for h-BN added sample is almost overlapping the J(c)(H) dependence for the pristine MgB2 sample. On the other hand, J(c) for the samples added with c-BN is larger at high magnetic fields, while the decrease of J(c) at low H is very small. At T = 20 K, a J(c) of 10(2) A cm(-2) is determined for the sample with x(c-BN) = 0.005 at H = 58 kOe, and for the sample with x(c-BN) = 0.01 at 54 kOe. Magnetic relaxation measurements indicate a significant flux pinning enhancement in MgB2 samples added with c-BN. It is proposed that the disorder at the interface caused by the convenient lattice matching relationship between the lateral plane of the MgB2 crystal prism and the face of the c-BN crystal cube is responsible for the observed vortex pinning increase.

Tetragonal Sr2FeMoO6 powders were prepared by the sol gel and solid-state reaction methods. The structure, microstructure and magnetic characteristics of the double perovskite Sr2FeMoO6 in the form of as-prepared powders and classical sintered ceramics were analyzed and compared. Moreover, the magnetic properties of Sr2FeMoO6 ceramics obtained by sol gel and solid state reaction methods and sintered by the classical method were compared with those of Sr2FeMoO6 ceramics obtained by the same two methods, but sintered by the spark plasma sintering technique. The morphology of the powders obtained from the gel precursor and oxides mixture was characterized by homogeneity, as well as the grains shape and size. The powder prepared by the sol gel method was finer (particle average size of 0.6 mu m) than those obtained from oxides mixture (particle average size of 0.9 mu m). Sintered ceramics with tetragonal Sr2FeMoO6 phase were prepared from the two mentioned powders by classical sintering at 1200 degrees C, 2 h in 5%H-2/Ar. The pellets obtained from the gel powder exhibited higher magnetic characteristics than those derived from the oxides mixture. The saturation magnetization and the total magnetic moment of the samples prepared by the sol-gel method were M-sat=41.18 emu/g and mu(exp)/f.u.=3.26, respectively, while for the samples derived from the oxides mixture were M-sat=40.77 emu/g and mu(exp)/f.u=3.10. Also, Sr2FeMoO6 pellets sintered by the conventional method showed higher saturation magnetization values than those sintered by spark plasma sintering technique. (C) 2014 Elsevier Ltd and Techna Group S.r.l. All rights reserved.

Colloidal nanocrystals electronic energy levels are determined by strong size-dependent quantum confinement. Understanding the configuration of the energy levels of nanocrystal superlattices is vital in order to use them in heterostructures with other materials. A powerful method is reported to determine the energy levels of PbS nanocrystal assemblies by combining the utilization of electric-double-layer-gated transistors and advanced ab-initio theory.