Publications

Polyester fabrics modified with ZnO particles by electroless deposition were investigated by broadband dielectric spectroscopy in a parallel capacitor between 10(-2) and 10(7) Hz in a temperature interval from ca. 123 to 473 K. Textile samples were routinely characterized for the structure and interaction of the ZnO particles with the fiber surface. Since a textile fabric material is a mixture of air and fibers, the parameters taken into consideration should be called as effective ones. The deposition of ZnO particles lead to complex dielectric spectra and to the temperature dependence of the decomposed peaks following Arrhenius law.

Iron oxide-silica nanoparticles (IOSi-NPs) were prepared from a mixture of ferrous chloride tetrahydrate and ferric chloride hexahydrate dropped into a silica xerogel composite. The structure and morphology of the synthesized maghemite nanoparticles into the silica xerogel were analysed by X-ray diffraction measurements, scanning electron microscopy equipped with an energy dispersive X-ray spectrometer, and transmission electron microscopy. The results of the EDAX analysis indicated that the embedded particles were iron oxide nanoparticles. The particle size of IOSi-NPs calculated from the XRD analysis was estimated at around 12.5 nm. The average size deduced from the particle size distribution is 13.7 +/- 0.6 nm, which is in good agreement with XRDanalysis. The biocompatibility of IOSi-NPs was assessed by cell viability and cytoskeleton analysis. Histopathology analysis was performed after 24 hours and 7 days, respectively, from the intratracheal instillation of a solution containing 0.5, 2.5, or 5mg/ kg IOSi-NPs. The pathological micrographs of lungs derived from rats collected after the intratracheal instillation with a solution containing 0.5mg/kg and 2.5mg/ kg IOSi-NPs show that the lung has preserved the architecture of the control specimen with no significant differences. However, even at concentrations of 5mg/ kg, the effect of IOSi-NPS on the lungs was markedly reduced at 7 days post treatment.

The synthesis of nanoparticles with inhibitory and bactericidal effects represents a great interest in development of new materials for biological applications. In this paper we present for the first time the synthesis of Ca10-xSmx(PO4)(6)(OH)(2) nanoparticles at low temperature and primary tests concerning the adherence of Enterococcus faecalis ATCC 29212 (gram-positive bacteria). All the XRD peaks were indexed in accordance with the hexagonal HAp in P63m space group. The EDAX spectrum and elemental mapping of O, P, Ca, and Sm demonstrate that all the elements were homogeneously distributed in Ca Sm-10-x(x).(PO4)(6)(OH)(2) with x(Sm) = 0.03. The peaks at 347.3 eV, 532.1 eV, and 133.8 eV in the XPS spectra can be attributed to the binding energy of Ca 2p, O is, and P 2p. The peak at 1084.4 eV observed in Ca Sm-10-x(x)(PO4)(6)(OH)(2) was attributed to the Sm 3d(5/2). Bacterial adhesion was reduced on Ca Sm-10-x(x)(PO4)(6)(OH)(2) sample when compared to pure HAp (x(Sm) = 0) and significant differences in bacterial adhesion on pure HAp (x = 0) and Sm:HAp (x(Sm) = 0.01,x(Sm) = 0.03, and x(Sm) = 0.1) were observed. The bacterial adhesion decreased when the samarium concentrations increased. Finally, we demonstrate that the Sm: HAp nanopowder with x(Sm) > 0 showed high antibacterial activity against Enterococcus faecalis ATCC 29212.

The aim of this paper is quantitative characterization of a MnZn ferrite with Bi2O3 increasing addition using the Image-Pro Plus software from Media Cybernetics. The sample matrix is a ferrite with the following chemical composition: Mn0.54Zn0.37Fe2.06O4. We applied the conventional ceramic technology in order to obtain the samples. Thus, the raw materials, i.e. alpha Fe2O3, Mn3O4, and ZnO, in a molar ratio 53:28:19 were mixed in suitable proportions in a steel ball-mill using demineralized water. The mixture was burn off at 800 degrees C for 1 hour, in air. The pre-sintered powder was milled in steel ball-mill with increasing addition of Bi2O3 (0.00, 0.01, 0.03, 0.05, 0.07, 0.10, 0.30, 0.50 wt %). For quick references, the sample without bismuth ions was denoted and the samples with increasing concentrations were numbered from "1", "7".

Here we report the extraordinary thermal stability of Mg rich bimetallic nanoparticles (NPs), which is important for hydrogen storage technology. The enhanced NP stability is accomplished because of two critical improvements: (i) no void development within NPs (nanoscale Kirkendall effect) during their formation and (ii) suppressed Mg evaporation and NP hollowing during Mg hydrogenation at elevated temperature. The mechanism leading to the improved thermal stability of Mg-based bimetallic NPs is shown to be due to MgH2 hydride formation before evaporation can take place. These findings were tested for various compositions of Mg with Ni, Cu, and Ti, which are interesting combinations of materials for hydrogen storage systems. To achieve this we first demonstrate the synthesis mechanism of Mg-Ni and Mg-Cu NPs, which is well controlled at the single particle level, in order to accomplish multi-shell, alloy and intermetallic structures of interest for hydrogen storage tests. Aberration corrected transmission electron microscopy was carried out to unravel the detailed atomic structure and composition of the bimetallic NPs after production, processing, and hydrogenation. Finally, a simple and effective methodology is proposed for tuning the composition of the Mg-based bimetallic NPs based on the temperature-dependent nucleation behavior of NPs in the gas-phase.

Europium doped zinc oxide (Eu:ZnO) thin films have been obtained by pulsed laser deposition (PLD). 002 textured thin films were achieved on glass and silicon substrates, while hetero-epilayers and homo-epilayers have been attained on single crystal SrTiO3 and ZnO, respectively. X-ray Diffraction (XRD) was employed to characterize the Eu:ZnO thin films. Extended XRD studies confirmed the different thin film structural properties as function of chosen substrates.

Glass-ceramic superconductors in the Bi-Sr-Ca-Cu-O system were prepared by melt-quenching method in the presence of some additives (Pb, B). The studied glasses were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), thermogravimetric and differential thermal analysis (DTA/TGA) and differential scanning calorimetry (DSC). On the crystallized ceramics obtained by the annealing the glasses, transport resistance and XRD measurements were also done. The glass transition temperatures (T-g) was found to range in the 380-430 degrees C domain, followed by a set of exothermal effects that could be assigned to the crystallization of the superconducting phases. The nucleation and growth of the crystals is influenced by both the nature of the oxides used as additives and by their ratio. So, the samples doped with low amount of B (x=0.1 and 0.2) present obvious transitions at about 110 K, highlighting the presence of the 2223 phase in highest amount and well interconnected.

Multi-quantum well structures and Si wafers implanted with heavy iodine and bismuth ions are studied in order to evaluate the influence of stress on the parameters of trapping centers. The experimental method of thermostimullatedcurrents without applied bias is used, and the trapping centers are filled by illumination. By modeling the discharge curves, we found in multilayered structures the parameters of both 'normal' traps and 'stress-induced' ones, the last having a Gaussian-shaped temperature dependence of the cross section. The stress field due to the presence of stopped heavy ions implanted into Si was modeled by a permanent electric field. The increase of the strain from the neighborhood of I ions to the neighborhood of Bi ions produces the broadening of some energy levels and also a temperature dependence of the cross sections for all levels.

Recently, ZnO and natural polysaccharides have received more and more attention as interesting components for designing complex functional nanomaterials, key elements being their high occurrence and low-cost. In this chapter are presented possibilities for tailoring the ZnO properties by using polysaccharides in the synthesis process as well as reports on the functionalization of cellulose-based natural fabrics with ZnO. In both cases, in the preparation step were used only simple and scalable wet chemical methods. The resulting materials with suitable characteristics, e.g. dependence of the ZnO nanostructures optical properties on their morphology or high-UV blocking and superhydrophobicity for ZnO-functionalized fabrics, can find applications in domains where such qualities are required.

We consider a varied-dimension InGaAs/GaAs structure of quantum well - nanobridge (NB) - quantum dot embedded in a "virtual" cylinder Omega. Electron and hole eigenstates are computed for the whole system using the finite volume method and effective mass approximation. Hybrid states and significant oscillator strength changes appear in the combined system at small values of the NB length under the Dirichlet boundary conditions imposed on the boundaries of Omega.