Publications

The electronic structure and magnetic properties of Zr2CoAl bulk material were investigated within the Density Functional Theory (DFT) framework. The material, basically a complete spin polarized half-metallic ferromagnet in the ground state, crystallizes in the ordered full-Heusler inverse structure (Hg2CuTi-type structure). The energy band gap, localized in minority spin channel is 0.48 eV at equilibrium lattice parameter, 6.54 angstrom. The total magnetic moment calculated, equal to 2 mu(B)/f.u., is an integral, in agreement with the Slater-Pauling curve for full-Heusler alloys. (C) 2014 Elsevier B.V. All rights reserved.

A case where the electrode polarization occurs in dielectric spectroscopy measurements carried out on a liquid crystal cell in which there are paired ions with different transport properties in the presence of generation-recombination processes is discussed. The processes of adsorption/desorption take place at blocking electrode surfaces with different features. The theoretical approach consists in introducing new independent variables with simple significance and in reformulating the fundamental equation for the concentrations of charge carriers and Poisson equation for the electric field. The main purpose of the present mathematical method is to obtain a more convenient analytical expression of admittance and complex permittivity in a form that is easy to use for the interpretation of the experimental data. The expression of the admittance allows suggesting an equivalent electrical circuit according to the processes occurring in the sample volume and at the surface electrodes. The analytical form of the admittance highlights a distinctive term that is proportional to one adimensional parameter which estimates the relative effects of the bulk process in comparison with the interfaces process. Several cases are analyzed and for each an analytical expression is found. In some cases the formulas are available in a simple form.

The aim of this study was to obtain membranes with antimicrobial activity presenting a complex sandwich-type structure. The outer layers are comprised of poly(methyl methacrylate) membranes, whereas the inner active layer consists of a modified commercial membrane to achieve antimicrobial properties. This activity arises due to the presence of silver nanoparticles in a material with a hybrid composition deposited on a commercial membrane. This hybrid material consists of polymer colloids and multiwall carbon nanotubes used for both the stabilization of the active layer by the interconnections of the polymer particles and as active component. The filtration tests revealed a good stability of the materials and an increased hydrophilicity of the hybrid membranes. The antimicrobial properties have been evaluated using Staphylococcus aureus and Escherichia coli, and have been correlated with the content and migration rate of silver ions.

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.

Superconducting bulk discs, S, of 20 mm in diameter and 3.5 or 3.3 mm thickness of MgB2 (pristine or added with cubic BN, respectively) with density above 97% were prepared by Spark Plasma Sintering. Discs were combined in a pair-type sandwich-like arrangement with a permanent NdFeB axially magnetised magnet, PM (similar to 0.5 T). Measurement of the trapped field, B-tr, with temperature, time, and the reduction rate of the applied magnetic field was performed using a Hall sensor positioned at the centre between the superconductor and the permanent magnet. It is shown that the permanent magnet with certain polarity favors higher trapped field of the superconductor owing to suppression of flux jumps specific for high density MgB2 samples. The B-tr of the PM-S pair was 2.45 T (20 K) and 3.3 T (12 K). (C) 2014 Elsevier B.V. All rights reserved.

This paper reports the systematic investigation of europium doped hydroxyapatite (Eu:HAp). A set of complementary techniques, namely Fourier Transform Infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM) and the Brunauer-Emmett-Teller (BET) technique were used towards attaining a detailed understanding of Eu:HAp. The XPS analysis confirmed the substitution of Ca ions by Eu ions in the Eu:HAp samples. Secondly, Eu:HAp and pure HAp present type IV isotherms with a hysteresis loop at a relative pressure (P/P-0) between 0.4 and 1.0, indicating the presence of mesopores. Finally, the in vitro biological effects of Eu:HAp nanoparticles were evaluated by focusing on the F-actin filament pattern and heat shock proteins (Hsp) expression in HEK293 human kidney cell line. Fluorescence microscopy studies of the actin protein revealed no changes of the immunolabelling profile in the renal cells cultured in the presence of Eu:HAp nanoparticles. Hsp60, Hsp70 and Hsp90 expressions measured by Western blot analysis were not affected after 24 and 48 hours exposure. Taken together, these results confirmed the lack of toxicity and the biocompatibility of the Eu:HAp nanoparticles. Consequently, the possibility of using these nanoparticles for medical purposes without affecting the renal function can be envisaged.

Nitrogen-doped titanium oxide thin films covered by gold metal nanoparticles were grown on (001) SiO2 quartz substrates by pulsed laser deposition. A KrF* excimer laser source (lambda = 248 nm, tau (FWHM) a parts per thousand currency sign 25 ns, nu = 10 Hz) was used for the irradiation of TiO2 and gold metal targets. The experiments were performed in controlled reactive oxygen or nitrogen atmosphere. The layers were grown for photocatalytic applications. Evaluation of photocatalytic activity was performed by photodegradation of methyl orange under near-UV light irradiation. Our results show that nitrogen doping and addition of gold nanoparticles have complementary effects, photoactivity being significantly improved as compared to that of pure titanium oxide.

We address the existence of steady state Green-Keldysh correlation functions of interacting fermions in mesoscopic systems for both the partitioning and partition-free scenarios. Under some spectral assumptions on the non-interacting model and for sufficiently small interaction strength, we show that the system evolves to a NESS which does not depend on the profile of the time-dependent coupling strength/bias. For the partitioned setting we also show that the steady state is independent of the initial state of the inner sample. Closed formulae for the NESS two-point correlation functions (Green-Keldysh functions), in the form of a convergent expansion, are derived. In the partitioning approach, we show that the 0(th) order term in the interaction strength of the charge current leads to the Landauer-Buttiker formula, while the 1(st) order correction contains the mean-field (Hartree-Fock) results.

(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.