National Institute Of Materials Physics - Romania

Thin films composed of graphene-based materials exhibit promising functional properties for the development of high-performance devices in a wealth of applications. However, there are significant technological challenges which force one to search for alternative pathways of materials production and deposition. This paper reports the deposition of graphene oxide (GO) flakes on quartz substrates by using the ultraviolet matrix-assisted pulsed laser evaporation (MAPLE) technique in vacuum or controlled nitrogen gas environment. Water, which is highly transparent to UV radiation, was used as matrix solvent for the preparation of the MAPLE targets. The results reveal that GO platelets can be successfully transferred by MAPLE technique. Besides, the GO material experiences a significant deoxygenating process during deposition, leading to the formation of reduced GO. Numerical simulations also show that the thickness of GO platelets highly influences the deposition process and the structure of the immobilized material. Thick enough aggregates can reach temperatures of thousands of degrees and undergo a large degradation in their structure.

Phenylboronic-acid-modified nanoparticles (NPs) are attracting considerable attention for biological and biomedical applications. We describe here a convenient and general protocol for attaching multiple copies of para-substituted phenylboronic acid moieties onto either iron-oxide-, silica-or diamond-derived NPs. The boronic acid fiinctionalized NPs are all fabricated by first modifying the surface of each particle type with 4-azidobenzoic ester functions. These azide-terminated nanostructures were then reacted with 4-[1-ozo-4-pentyn-1-yl) amino]phenylboronic acid units via a Cu(I) catalyzed Huisgen cycloaddition to furnish, conveniently, the corresponding boronic-acid modified NPs (or "borono-lectins") targeted in this work. The potential of these novel "borono-lectins" as antiviral inhibitors was investigated against the Hepatitis C virus (HCV) exploiting a bioassay that measures the potential of drugs to interfere with the ability of cell-culture-derived JFH1 virus particles to infect healthy hepatocytes. As far as we are aware, this is the first report that describes NP-derived viral entry inhibitors and thus serves as a "proof-of-concept" study. The novel viral entry activity demonstrated, and the fact that the described boronic-acid-functionalized NPs all display much reduced cellular toxicities compared with alternate NPs, sets the stage for their further investigation. The data supports that NP-derived borono-lectins should be pursued as a potential therapeutic strategy for blocking viral entry of HCV.

Epitaxial Pb(Zr0.2Ti0.8)O-3 layers of good structural quality were grown on single crystal SrTiO3 substrates. The pyroelectric coefficient was estimated from the signal generated by the ferroelectric film working as a pyroelectric detector in the voltage mode, without pre-poling procedure. The obtained value is as high as 1.9 x 10(-3) C/m(2) K. The large value is attributed to the presence of 90 degrees ferroelectric domains and to the compressive misfit strain, leading to an enhanced ferroelectric polarization. (C) 2013 AIP Publishing LLC.

A systematic experimental study of the main challenges for silicon-pixel sensors at the European XFEL is presented. The high instantaneous density of X-rays and the high repetition rate of the XFEL pulses result in signal distortions due to the plasma effect and in severe radiation damage. The main parameters of X-ray-radiation damage have been determined and their impacton p(+)n sensors is investigated. These studies form the basis of the optimized design of a pixel-sensor for experimentation at the European XFEL. (C) 2013 Elsevier B.V. All rights reserved.

Radiation damage in silicon, caused by the creation of point and cluster defects due to energetic charged hadrons and neutrons, results in a serious degradation of silicon-sensor performance and limits their lifetime. So far not all the defects are understood. The work presented here focuses on the study of radiation damage by electrons of different kinetic energies, from 1.5 MeV to 15 MeV, in order to study the differences between point- and cluster-related defects. The introduction rate of vacancy-related point defects and of so-called clustered regions was investigated as a function of electron energy. It is shown that the ratio between cluster dominated and point defect formation increases with increasing electron energy. 1.5 MeV electrons create only point defects, and the formation of cluster defects starts already at 3.5 MeV. To study the defect kinetics, isothermal annealing at 80 degrees C and isochronal annealing measurements were performed. (C) 2013 Elsevier B.V. All rights reserved.

Tetragonal alpha-FeSe flakes were fabricated by a simple method. Enhancement of superconductivity was observed in the quenched samples. The properties were characterized by X-ray diffraction, a superconductivity quantum interference device, and physical property measurement system. It is interesting that the superconducting transition temperature of the quenched samples is about 2 K higher than that of unquenched samples, but after reannealed, the enhancement of superconductivity disappeared. The reduction of the c/a ratio might be responsible for the enhancement of superconductivity in the quenched FeSe flakes.

Adhesion to substrate and antimicrobial efficiency of pulsed laser-deposited ZnO nanostructures were significantly increased by interposing a buffer nano-layer of hydrophobin. The hydrophobin interlayer increased by eight times the ZnO film resilience to wash in water, while in alkaline or acidic artificial sweat, it increased by 2 and 1.2 times, respectively, as compared to textiles covered with ZnO films only. Hydrophobin boosted the biocide effect of ZnO nanostructured films in case of Candida albicans and mold mix inoculum cultures by 50 and 30 %, respectively. An interpretation of these phenomena is advanced based upon the results of the structural investigations.

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.