Publications

Radio-frequency Plasma Enhanced Chemical Vapour Deposition (in different methane dilutions) was used to synthesize adherent and haemocompatible diamond-like carbon (DLC) films on medical grade titanium substrates. The improvement of the adherence has been achieved by interposing a functional buffer layer with graded composition TixTiC1-x (x = 0-1) synthesized by magnetron co-sputtering. Bonding strength values of up to similar to 67 MPa have been measured by pull-out tests. Films with different sp(3)/sp(2) ratio have been obtained by changing the methane concentration in the deposition chamber. Raman spectroscopy, X-ray photoelectron spectroscopy and X-ray diffraction were employed for the physical-chemical characterization of the samples. The highest concentration of sp(3)-C (similar to 87 %), corresponding to a lower DLC surface energy (28.7 mJ/m(2) ), was deposited in a pure methane atmosphere. The biological response of the DLC films was assayed by a state-of-the-art biological analysis method (surface enhanced laser desorption/ionization-time of flight mass spectroscopy), in conjunction with other dedicated testing techniques: Western blot and partial thromboplastin time. The data support a cause-effect relationship between sp(3)-C content, surface energy and coagulation time, as well as between platelet-surface adherence properties and protein adsorption profiles.

A high-performance polymeric nanostructured sensing layer for a surface acoustic wave sensor, deposited using a modified matrix assisted pulsed laser evaporation direct write technique, exhibited improved performance in terms of response time and frequency deviation. In the present work, we assessed the factors and mechanisms that account for the layer's increased sensing capabilities. The increase in the sensing performance was attributed to an increased diffusion constant, due to greater molecular mobility of polymeric chains caused by the nanoparticles embedded in the polymer matrix.

Experimental results for the carrier capture and relaxation dynamics in self-organized semiconductor quantum dots are analyzed using a microscopic theory. Time-resolved differential transmission changes of the quantum-dot transitions after ultrafast optical excitation of the barrier states are studied in a wide range of carrier temperatures and excitation densities. The measurements can be explained by quantum-dot polaron scattering and their excitation-dependent renormalization due to additional Coulomb scattering processes. Results of configuration-picture and single-particle-picture descriptions, both with nonperturbative transition rates, show good agreement with the experiments while Boltzmann scattering rates lead to a different excitation density and temperature dependence.

This paper analyses in detail the core levels evolution of Pb(Zr,Ti)O-3, i.e. Pb 4f, Zr 3d, Ti 2p, O 1s in various conditions: absolutely freshly prepared sample, sample stored under air, and the effects of in vacuum annealing. The aim of the study is to quantify separately the chemical reactivity at the surface and the band bending effects due to the ferroelectric polarization. It is found that freshly prepared samples present mostly inwards (down arrow) polarization. This phenomenon is mostly revealed by the Ti 2p and O 1s spectra, manifested as a distinct component with 1.8 eV lower binding energy in the O 1s binding energy and by 1.1 eV in the Ti 2p binding energy. Sample aging under air suppresses the inwards polarization, and most signal comes from surfaces not presenting ferroelectric permanent polarization perpendicular to the sample surface. This process conducts also to the formation of Pb(CO3)(2) on the surface. Annealing to temperatures up to 400 degrees C stabilizes a surface composed by a main part of surface without polarization perpendicular to the surface, and with some areas presenting outwards (up arrow) polarization. These areas have, most probably, different terminations, the polarized area being (Ti,Zr)O-2 terminated. (C) 2013 Elsevier B.V. All rights reserved.

This paper deals with the synthesis of two nanohybrid materials based on maghemite (gamma-Fe2O3) and poly-DL-alanine using a two-step procedure consisting of maghemite nanoparticles synthesis by microemulsion method and nanohybrids obtaining by coating of maghemite nanoparticles with poly-DL-alanine biopolymer in two different molar ratios (H1:5 and H1: 15). The maghemite and their corresponding nanohybrids were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, X-ray photoemission spectroscopy, Mossbauer spectroscopy, Transmission electron microscopy, High resolution transmission electron microscopy with selected area electron diffraction and Atomic absorption spectroscopy. The two nanohybrids under the investigation have the average particle sizes of 22 nm and 23 nm. The Fourier transform infrared spectroscopy spectra and X-ray photoemission spectroscopy data indicate the existence of some interactions between the maghemite nanoparticles and poly-DL-alanine shell. The saturation magnetization values for maghemite and the two nanohybrids determined by a Vibrating Sample Magnetometer correspond to a typical superparamagnetic behavior suitable for applying in biomedical field. Also, with respect of biomedical application the biological activity of maghemite and its corresponding nanohybrids was investigated on healthy human cells (PBMC) and cancerous cells (HeLa). Furthermore, in order to support the multifunctionality of the gamma-Fe2O3 sample and nanohybrids we also investigated their wastewater treatment properties by measuring the removal efficiency of heavy metal Cd (II) ions. (C) 2013 Elsevier B. V. All rights reserved.

Ge-SiO2 films with high Ge/Si atomic ratio of about 1.86 were obtained by co-sputtering of Ge and SiO2 targets and subsequently annealed at different temperatures between 600 and 1000 C in a conventional furnace in order to show how the annealing process influences the film morphology concerning the Ge nanocrystal and/or amorphous nanoparticle formation and to study their electrical behaviour. Atomic force microscopy (AFM) imaging, Raman spectroscopy and electrical conductance measurements were performed in order to find out the annealing effect on the film surface morphology, as well as the Ge nanoparticle formation in correlation with the hopping conductivity of the films. AFM images show that the films annealed at 600 and 700 C present a granular surface with particle height of about 15 nm, while those annealed at higher temperatures have smoother surface. The Raman investigations evidence Ge nanocrystals (including small ones) coexisting with amorphous Ge in the films annealed at 600 C and show that almost all Ge is crystallized in the films annealed at 700 C. The annealing at 800 C disadvantages the Ge nanocrystal formation due to the strong Ge diffusion. This transition in Ge nanocrystals formation process by annealing temperature increase from 700 to 800 C revealed by AFM and Raman spectroscopy measurements corresponds to a change in the electrical transport mechanism. Thus, in the 700 C annealed films, the current depends on temperature according to a T-1/2 law which is typical for a tunnelling mechanism between neighbour Ge nanocrystals. In the 800C annealed films, the current-temperature characteristic has a T-114 dependence showing a hopping mechanism within an electronic band of localized states related to diffused Ge in SiO2. (C) 2013 Elsevier B.V. All rights reserved.

We present a node-centered finite volume method for computing a representative range of eigenvalues and eigenvectors of the Schrodinger operator on a three-dimensional cylindrically symmetric bounded domain with mixed boundary conditions. The three-dimensional Schrodinger operator is reduced to a family of two-dimensional Schrodinger operators distinguished by a centrifugal potential. We consider a uniform, boundary conforming Delaunay mesh, which additionally conforms to the material interfaces. We study how the anisotropy of the effective mass tensor acts on the uniform approximation of the first K eigenvalues and eigenvectors and their sequential arrangement. There exists an optimal uniform Delaunay discretization with matching anisotropy with respect to the effective masses of the host material. For a centrifugal potential one retrieves the theoretically established first-order convergence, while second-order convergence is recovered only on uniform grids with an anisotropy correction. (C) 2013 Elsevier Inc. All rights reserved.

To study the suitability of using graphite as material for high-power targets for rare isotope production at the future Facility for Rare Isotope Beams (FRIB) in the USA and at the Facility for Antiproton and Ion Research (FAIR) in Germany, thin foils of polycrystalline graphite were exposed to 8.6-MeV/u Au ions reaching a maximum fluence of 1 x 10(15) ions/cm(2). Foil irradiation temperatures of up to 1800 degrees C were obtained by ohmic heating. In-situ monitoring of the electrical resistance of the graphite foils during and after irradiation provided information on beam-induced radiation damage. The rate of electrical resistance increase as a function of fluence was found to decrease with increasing irradiation temperature, indicating a more efficient annealing of the irradiation-produced defects. This is corroborated by the observation that graphite foils irradiated at temperatures below about 800 degrees C showed cracks and pronounced deformations, which did not appear on the samples irradiated at higher temperatures. (C) 2013 Elsevier B.V. All rights reserved.