National Institute Of Materials Physics - Romania

We report on the fabrication of silicon-reinforced carbon (C: Si) structures by combinatorial pulsed laser deposition to search for the best design for a new generation of multi-functional coated implants. The synthesized films were characterized from the morphological, structural, compositional, mechanical and microbiological points of view. Scanning electron microscopy revealed the presence, on top of the deposited layers, of spheroid particulates with sizes in the micron range. No microcracks or delaminations were observed. Energy dispersive x-ray spectroscopy and grazing incidence x-ray diffraction pointed to the existence of aC to Si compositional gradient from one end of the film to the other. Raman investigation revealed a relatively high sp(3) hybridization of up to 80% at 40-48 mm a part from the edge with higher Ccontent. Si addition was demonstrated to significantly increase C: Si film bonding to the substrate, with values above the ISO threshold for coatings to be used in high-loading biomedical applications. Surface energy studies pointed to an increase in the hydrophilic character of the deposited structures along with Si content up to 52 m Nm(-1'). In certain cases, the Si-reinforced Ccoatings elicited an antimicrobial biofilm action. The presence of Si was proven to be benign to HEp-2 cells of human origin, without interfering with their cellular cycle. On this basis, reliable C: Si structures with good adherence to the substrate and high efficiency against microbial biofilms can be developed for implant coatings and other advanced medical devices.

Based on simulations using the plane-wave expansion method, we show that the position of the first bandgap for TM polarized electromagnetic radiation in a high-filling ratio two-dimensional square photonic crystal is practically insensitive to the shape of dielectric rods with the same cross-sectional area. The width of this bandgap depends on the rod shape, but the difference between photonic crystals with circular and regular polygonal rod shapes with a number of edges higher than six can be neglected. For higher-order bandgaps the difference is larger. These results suggest that the fabrication tolerances related to the shape of dielectric rods in a PBG are not as strict as previously thought. (C) 2017 Elsevier B.V. All rights reserved.

In: ZnO (IZO) thin films were deposited on flexible plastic substrates by pulsed laser deposition (PLD) method. The obtained layers present adequate optical and electrical properties competitive with those based on indium tin oxide (ITO). The figure of merit (9 X 10(-3) Omega(-1)) calculated for IZO layers demonstrates that high quality coatings can be prepared by this deposition technique. A thermal annealing (150 degrees C for 1 h) or an oxygen plasma etching (6 mbar for 10 min.) were applied to the IZO layers to evaluate the influence of these treatments on the properties of the transparent coatings. Using vacuum evaporation, organic heterostructures based on cooper phthalocyanine (CuPc) and 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) were deposited on the untreated and treated IZO layers. The optical and electrical properties of the heterostructures were investigated by UVVis, FTIR and current-voltage (I-V) measurements. For the heterostructure fabricated on IZO treated in oxygen plasma, an improvement in the current value with at least one order of magnitude was evidenced in the I-V characteristics recorded in dark conditions. Also, an increase in the current value for the heterostructure deposited on untreated IZO layer can be achieved by adding an organic layer such as tris-8-hydroxyquinoline aluminium (Alq(3)).

Significant differences are reported for the IR spectra of poly[(2,5-bisoctyloy)-1, 4-phenylenevinylene] (BO-PPV) recorded onto the KBr, Ag and Au supports. In this work, a decrease in the absorbance of the IR spectra of the BO-PPV films deposited onto Au and Ag supports as increasing the macromolecular compound film thickness is reported. A preferential orientation of the BO-PPV molecules and its composite with single-walled carbon nanotubes (SWNTs) versus metallic supports of Ag and Au is assessed using the IR absorption spectroscopy under s and p polarized light. An anti-Stokes photoluminescence (ASPL) is reported to characterize the BO-PPV macromolecular compound. The BO-PPV ASPL spectra intensity dependent both of the thickness of the macromolecular compound layer deposited onto the metallic supports and the SWNTs weight in the BO-PPV/SWNTs composite mass. (C) 2017 Elsevier B.V. All rights reserved.

This paper relates to a method for the preparation of lead acetate film and its use as precursor for twostep solution deposition of CH3NH3PbI3 perovskite film. For the preparation of perovskite film, lead acetate was used both in the form of trihydrate and dehydrated. The effects of lead acetate trihydrate dehydration on the structure of the resulted perovskite films were studied. The prepared perovskite films which consist of cuboid grains, show high surface coverage both on FTO and TiO2 substrates. XRD measurements have not revealed the presence of the PbI2 contaminant in perovskite film. Solvent vapor annealing method was employed to prepare perovskite film that contains lead iodide. Using impedance spectroscopy measurements, we further evaluated the influence of the prepared perovskite films on the performance of the photovoltaic devices. (C) 2017 Elsevier Ltd. All rights reserved.

The enhancement of the Raman scattering in Cs3Bi2I9 is evaluated by the ratio I-T/I-300K between the relative intensities of the Raman line peaked at 146cm(-1), when the spectra are recorded in the temperature range of 88-300K, as a signature of exciton-phonon interactions. In the resonant and nonresonant conditions, excitation wavelengths 476, 561, and 660nm, respectively, are used in order to overlap with great accuracy the bands disclosed by diffuse reflection, photoconductivity (PC), photoluminescence (PL), and photoluminescence excitation (PLE) spectra. Based on the experimental analyses, the strength of exciton-phonon interaction is dependent on the defects in the crystal and the type-range interaction of the excitations in an independent Bi2I93- cluster. The noticeable PL band, attributed to excitons trapped on different stacking faults, manifests some defects in crystal that diminish the movement of excitons. This effect significantly decreases the overlaps of excitons with the phonons, resulting in a reduced exciton-phonon coupling.

In this paper the influence of the heat treatment on the structural and optical properties of oxide single layer and multilayer transparent thin film structures of ITO/Au/ITO, AZO/Au/AZO, TiO2/Au/TiO2 and Bi2O3/Au/Bi2O3 type is studied. The single-layer oxides and respective multilayer structures have been deposited on glass substrates by successive DC magnetron sputtering using metallic targets ln:Sn, Zn:Al, Ti and Bi, in reactive (for the oxide films) or inert (for the metallic Au interlayer films) atmosphere. Good quality transparent conducting thin film structures have been obtained, with resistivity similar to 10(-4) Omega cm and transmittance similar to 75%. The wetting surface properties in function of time exposure at UV radiation (254 nm) have been also studied before and after heat treatment performed at 450 degrees C. (C) 2017 Elsevier Ltd. All rights reserved.

We present a comparative study between the properties of Yb3+/Er3+ co-doped LiYF4 thin films obtained by pulsed laser deposition (PLD) and matrix-assisted pulsed evaporation (MAPLE) growth techniques, respectively. We performed structural, morphological, and optical analyses in order to draw a conclusion about the potential of MAPLE as a growth technique used for the obtaining of RE-doped fluoride thin films having up-conversion properties. For both techniques the surface morphology is typical for laser processed thin films of RE-doped fluorides, with roughness values of the order of few hundreds of nanometers and a higher density of defects in the sample obtained by MAPLE. Up-conversion properties do not exhibit major differences between the thin film samples and the pressed target. Under 980 nm laser light pumping, both Yb3+/Er3+ co-doped LiYF4 thin film samples, obtained by PLD and MAPLE, show green ((H-2(11/2), S-4(3/2)) -> I-4(15/2)) and red (F-4(9/2) -> I-4(15/2)) up-conversion luminescence explained by a two-photon processes. Therefore MAPLE is a viable growth technique for the fundamental study of RE-doped fluoride thin films and their respective functional properties. (C) 2017 Elsevier B.V. All rights reserved.

New composite materials based on single-walled carbon nanotubes effectively separated into semiconducting (S-SWNTs) and metallic tubes (M-SWNTs) and poly(ortho-phenylenevinylene) (POPV) were synthesized by the electrochemical polymerization of the alpha,alpha,alpha',alpha',-tetrabromo-o-xylene monomer onto the surface of Au supports covered with carbon nanotubes films. Using FTIR spectroscopy, an increase of the quinoid structure weight is highlighted when a charge transfer is induced to take place between the two constituents of the POPV/S-SWNT composite material. In addition, a down-shift of the Raman line belonging to POPV (from 530 cm-(1) to 515 cm(-1)), which was accoinpanied by an increase in relative peak intensity, is reported as a result of steric hindrance effects induced by the covalent bonding of POPV onto the S-SWNT surface. The non-covalent functionalization of M-SWNTs with POPV is demonstrated to occur by Raman scattering and FTIR spectroscopy. The photoluminescence (PL) spectrum of POPV exhibits two bands at 2.82 and 2.25 eV, which were assigned to the electronic emission transitions of macromolecular chains having 3 and 7-10 repeating units, respectively. We demonstrate that POPV photoluminescence quenching in the presence of M + S-SWNTs, M-SWNTs and S-SWNTs is achieved by tubes with chirality (14,7), (12,10) and (11,9), respectively. (C) 2017 Elsevier Ltd. All rights reserved.

The performance of the poly(2, 2'-bithiophene-co-pyrene) copolymer doped with bis(2-ethyl hexyl) sulfosuccinate sodium (AOT) anions [(PBTh-Py)(+)AOT(-)] and its composite with single-walled carbon nanotubes (SWNTs) [(PBTh-Py)(+)AOT(-)/SWNTs] as active materials for the electrodes of symmetrical supercapacitors is demonstrated in this work. Using cyclic voltammetry, the influence of the electrolyte concentration and the different cations on the oxidation and reduction processes at the electrolyte/electrode interface is reported. Using charge-discharge galvanostatic measurements in the case of the symmetrical-supercapacitors having as electrode active materials, the (PBTh-Py)(+)AOT(-) copolymer and the (PBTh-Py)(+)AOT(-)/SWNTs composite, values of the specific capacitance equal with 11.5 and 59 F g(-1), respectively, for current densities of 100 mA g(-1), were reported.