National Institute Of Materials Physics - Romania

The paper reports on the main findings issued from studying the formation of adsorbed micelle-like clusters of ionic surfactant (sodium dodecyl sulfate and hexadecyl trimethylammonium bromide) onto molecule of collagenous polypeptide (collagen hydrolyzates and calfskin collagen type 1). Capillary viscometry, UV-circular dichroism, transmission electron microscopy and surfactant titration method were used to characterize the macromolecular component of the studied systems. To highlight the critical aggregation concentration (cac) and the critical saturation concentration (T-2) in the investigated polypeptide-surfactant systems, the steady-state fluorescence of pyrene (1(1)/1(3) rule) and the surface tension measurements (the droplet volume method) were availed. The study revealed a significant decrease of the effective micelle concentration of surfactant (cue) in the presence of polypeptide irrespective of pH and a critical concentration T-2 depending on the system composition and pH.

The interactions by which ions lose their energy in silicon are investigated at the microscopic level. this theoretical study put in evidence that the ionization could also represent a source of structural defects, and, contrary to the processes initiated by elementary particles, could generate extended primary defects, as, e.g. four-fold coordinated defects, due to the simultaneous breaking of bond for more neighbouring atoms in the lattice in a single interaction, in the ionisation core. The average energy transferred per atom is calculated, and also the energy spent by ionisation. The time dependence of the temperature in the ionisation core is derived in some simplifying assumptions. These contributions not considered yet in the studies of degradation of silicon detectors in radiation fields and could account for the discrepancies observed between models and measurements at microscopic versus device level for hadrons and ions. (C) 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

The aim of this study was to provide and characterize nanostructured TiO2 films for application in the depollution of the contaminated water against Escherichia coli (E. coli). The nanometric size of particles and the porosity of the films have been correlated with the technological parameters of the deposition process. For this aim three-layer TiO2 films were deposited by sol-gel and dip-coating method on SiO2/glass substrate. Iron (1 and 7%) and polyethylene glycol (PEG(600)) (0.014-0.110 M) were added to the coating solutions to study their effect on the porosity of the samples and respectively on the amorphous to anatase phase transition, as well as on the antibacterial activity. The samples were characterized using different complementary methods such as X-ray Diffraction (XRD), Spectroscopic Ellipsometry (SE), Atomic Force Microscopy (AFM), dynamics (growth and adherence) of E. coli development versus nanofilm composition (where the amount of bacterial inoculums used was closer to those Found in wasted waters). The obtained films have shown low toughness (values bellow 0.74 nm) and the particle size in nanometric range. The direct optical band gap values increases with the Fe content tip to 2.64 eV (470 nm), leading to an active photocatalyst tinder visible light (in our case under natural illumination condition). The inhibitory effect towards the E. Coli is Correlated with PEG and Fe concentration and was found to he the strongest for the sample containing 0.069 M PEG.

Hydroxyapatite (HAp) films, widely used as a biocompatible material for hard tissues repairing. are studied in this paper for a better control and understanding of the crystallization and densification of sol-gel deposited layers. Calcium nitrate and triethyl phosphite diluted in alcohols were used as calcium and phosphorus precursors. HAp coatings were obtained by spinning method, followed by drying and annealing in the range 130-750 degrees C. Specific temperatures of the chemical reactions of HAp formation have been revealed by thermogravimetric analysis (TG-DTA). Structural. chemical and optical characterizations of the films were performed by Scanning Electron Microscopy (SEM) with Energy Dispersive X-ray Analysis (EDX) facilities, X-ray diffraction (XRD). Fourier Transform Infrared Spectroscopy (FTIR) and Spectral Ellipsometry (SE). The film crystallinity increases with file annealing temperature above 550 degrees C. XRD lines of HAp crystallographic planes become narrow at 750 degrees. and correspond to a single crystallographic phase. The Film morphology depends not only on annealing history but also on the synthesis parameters. Thus. layers with large grains of well sinterized HAp nano-crystals can be obtained. Using EDX measurements, the Ca/P ratio was found close to the stoichiometric value in the well sinterized HAp grain regions and slightly increased 1.82 for boundary regions between grains. The density of pores usually observed in sol-gel derived films was estimated for different samples using modeling of SE data.

In this communication, we study the production of defects by energetic ions in silicon and germanium, at very low temperatures, as dependencies of non-ionizing energy loss and number of displacements on the ion kinetic energy, and also the partition of the energy deposited between ionization, creation of defects and phonons, short time after the interaction.

ZnO is a wide band-gap (ca. 3.4 eV) semiconductor, piezoelectric, pyroelectric, biocompatible, transparent in the visible spectrum and UV light emitting material. The fabrication in 2001 of the first nanobelts of semiconductor oxide materials lead to a rapid expansion of researches concerning one dimensional nanostructures (nanotubes, nanowires, nanobelts), given their possible application in optics, optoelectronics, piezoelectricity, catalysis. Researches carried on up to date evidenced the possibility to obtain an extraordinary variety of ZnO nanostructures, in function of the experimental parameters and the used growth methods. In this work we present morphostructural results on nanostructured ZnO layers obtained by electrochemical deposition. The films have been grown on gold covered glass plates and Si wafers, in various experimental conditions such as: nature of the wetting agents, electrical polarization of the substrate (continuous, pulsed). The influence of the growth conditions on the crystalline structure and morphology of the films is revealed by scanning and transmission electron microscopy studies. The films show a variety of growth morphologies, from entangled-wires-like to honeycomb-like layers. These large-specific-surface layers will be tested as nanostructured substrates for photovoltaic cells with improved efficiency.

Iron- and europium-doped (<= 1 at.%)TiO2 nanoparticles powders have been synthesized by a hydrothermal route at 200 degrees C, starting with TiCl4, FeCl3 center dot 6H(2)O and EuCl3 center dot 6H(2)O. The structure, morphology and optical peculiarities were investigated by means of X-ray diffraction (XRD), transmission electron microscopy (TEM), extended X-ray absorption fine structure (EXAFS), Mossbauer spectroscopy and UV-vis measurements. The photocatalytic performance was analysed in the photodegradation reaction of phenol. Rietveld refinements of XRD patterns reveal that the as-prepared samples consist in iron- and europium-doped TiO2 in the tetragonal anatase structural shape, with particle size as low as 15 nm. By means of Mossbauer spectroscopy on both Fe-57 and Eu-151 isotopes as well as by EXAFS analyses, the presence of Fe3+ and/or Eu3+ ions in the nanosized powders has been evidenced. It was found that iron and europium ions can substitute for titanium in the anatase structure. From the UV-vis reflection spectra, by using the transformed Kubelka-Munk functions, the band gap energy (E-g) of the hydrothermal samples has been determined in comparison with that of Degussa P-25 photocatalyst. A decrease of E-g from 2.9eV found for Degussa photocatalyst to 2.8 eV for the titania doped with 1 at.% Fe has been evidenced, indicating a valuable absorption shift (similar to 20 nm) towards visible light region. However, the best photocatalytic activity in the photodegradation reaction of phenol was evidenced for the hydrothermal sample, TiO2: 1 at.% Fe, 0.5 at.% Eu, in both UV and visible light regions. The photocatalytic activities of iron-doped and iron-europium-codoped samples are high and practically the same only in visible light. The photocatalytic properties in Correlation with the structural and optical peculiarities of the hydrothermal samples are discussed. (C) 2008 Elsevier B.V. All rights reserved.

The nanostructure of Si-x(SiO2)(1-x) films deposited on quartz substrate, where x varies from 0 to 1, was determined by high-resolution transmission electron microscopy in the sample regions with x approximate to 0.1, 0.2. 0.5. and 0.75. In the Si-0.5(SiO2)(0.5) region, the formation of a Si nanocrystallite network was established. At high concentrations of Si nanocrystallites, nanotwins and stacking faults occurred in the crystallites. Large Si crystallites appeared at x >= 0.5 in the quartz Substrate under the interface, while the film presented nanopores over the interface. The mechanisms for the formation of the nanocrystallites were discussed and correlated with the film properties.

Despite many investigations already performed with respect to sintering stability and grain growth vs. annealing conditions in low yttrium doped alpha- Al2O3 (150 ppm) - some fundamental questions are still open. These questions concern mainly the influence of small level of impurities at grain boundary in the sintering behavior and grains growth of the materials, i.e. the microstructure function of the annealing time at annealing temperature of 1650 degrees C. The low yttrium doped alpha- Al2O3 (150 ppm) samples were sintered and annealed at high temperatures. Besides conventional micro structural studies, such as grain diameter and grain size functions of distribution of the annealing temperature were studied by electron microscopy investigations and statistical measurement. The implications of the different microstructures with respect to micro structural stability have discussed and compared to observations described in the literature.