Publications

Herein, we investigate the emission properties of Er - BiOCl in the range of similar to 500 to 1700 nm under down - (488 and 973 nm) and NIR (telecom - wavelength at similar to 1500 nm) up - conversion excitation as well high energy X-ray excitation. The dependencies of red (similar to 670 nm) and NIR (similar to 800 nm) to green emission (similar to 543 nm) ratio with Er concentration, excitation mode and delay after laser pulse as well as the up - conversion excitation spectra and decays are analyzed in terms of competitive ground state absorption/excited state absorption and energy transfer up - conversion mechanisms. The CIE chromaticity diagram show single excitation (similar to 1500 nm), delay induced emission color change from yellowish green (delay of 0.001 ms) to reddish orange (delay of 1 ms). The X-ray induced emission of Er - BiOCl presents an atypical red to green emission ratio that exceeds that measured under optical down - conversion excitation by a factor of 13. The potential of Er - BiOCl for optical/X-ray imaging applications is discussed. (C)2015 Optical Society of America

Although a great number of antibiotics are currently available, they are often rendered ineffective by the ability of microbial strains to develop genetic resistance and to grow in biofilms. Since many antimicrobial agents poorly penetrate biofilms, biofilm-associated infections often require high concentrations of antimicrobial agents for effective treatment. Among the various strategies that may be used to inhibit microbial biofilms, one strategy that has generated significant interest involves the use of bioactive surfaces that are resistant to microbial colonization. In this respect, we used matrix assisted pulsed laser evaporation (MAPLE) involving a pulsed KrF* excimer laser source (lambda = 248 nm, tau = 25 ns, nu = 10 Hz) to obtain thin composite biopolymeric films containing natural (flavonoid) or synthetic (antibiotic) compounds as bioactive substances. Chemical composition and film structures were investigated by Fourier transform infrared spectroscopy and X-ray diffraction. Films morphology was studied by scanning electron microscopy and transmission electron microscopy. The antimicrobial assay of the microbial biofilms formed on these films was assessed by the viable cell counts method. The flavonoid-containing thin films showed increased resistance to microbial colonization, highlighting their potential to be used for the design of anti-biofilm surfaces. (C) 2014 Elsevier B.V. All rights reserved.

The inhibiting action of O-ethyl-S-2-(2-hydroxy-3,5-diiodophenyl)-2-oxoethylxantogenate (EHDO) on the oxidation of FeS in air-saturated solutions at pH 1.3 and 25 degrees C was studied using potentiodynamic polarization and electrochemical impedance spectroscopy measurements. The uninhibited and inhibited surfaces were characterized by scanning electron microscopy, energy dispersive X-ray analysis and Raman spectroscopy. It was found that EHDO acts as an anodic inhibitor. Also, it was found that the corrosion of Fe(0) is slower than the oxidative dissolution of uninhibited FeS but faster than the oxidative dissolution of inhibited FeS. This behavior makes EHDO a potential inhibitor of the corrosion of Fe(0) when covered by FeS. (C) 2015 Elsevier B.V. All rights reserved.

This paper presents some studies about the preparation by matrix-assisted pulsed laser evaporation (MAPLE) technique of heterostructures with single layer of arylene based polymer, poly[N-(2-ethylhexy1)2.7-carbazoly1 vinylene]/AMC16 and poly[N-(2-ethylhexy1)2.7-carbazolyl 1.4-phenylene ethynylene]/AMC22, and with layers of these polymers mixed with Buckminsterfullerene/C-60 in the weight ratio of 1:2 (AMC16: C60) and 1:3 (AMC22: C60). The deposited layers have been characterized by spectroscopic (UV-Vis-NIR, PL, FTIR) and microscopic (SEM, AFM) methods. The effect of the polymer particularities on the optical and electrical properties of the structures based on polymer and polymer: C-60 mixed layer has been analyzed. The study of the electrical properties has revealed typical solar cell behavior for the heterostructure prepared by MAPLE on glass/ITO/PEDOT-PSS with AMC16, AMC22 and AMC22: C-60 layer, confirming that this method is adequate for the preparation of polymeric and mixed active layers for solar cells applications. The highest photovoltaic effect was shown by the solar cell structure realized with single layer of AMC16 polymer: g1a55/ITO/PEDOT-PSSIA1VIC16/A1. (C) 2014 Elsevier B.V. All rights reserved.

Magnetic titania nanoparticles covered/embedded in SiO2 shell/matrix were simultaneously manufactured by the single-step laser pyrolysis. The present study is a continuation of our previous investigations on the TiO2/Fe and TiO2/HMDSO (hexamethyldisiloxane) derived-systems. The aim of this work is to study the synthesis by IR (Infrared) laser pyrolysis of magnetic TiO2 based nanocomposites which implies many concurrent processes induced in the gas phase by the laser radiation. The dependence between characteristic properties and the synthesis parameters was determined by many analytical and complementary methods: XRD (X-ray diffraction) structural analysis, UV-vis (ultraviolet-visible) and EDAX (energy-dispersive X-ray) spectroscopy, TEM and HRTEM (transmission electron microscopy at low and high resolution) analysis and magnetic measurements. The results of analysis indicate the presence of disordered silica, Fe, alpha-Fe2O3 and mixtures of anatase and rutile phases with mean crystallite dimensions (in the 14-34 nm range) with typical character of diluted magnetic oxide systems and a lower bandgap energy (E-g = 1.85 eV) as compared with TiO2 P25 Degussa sample. (C) 2014 Elsevier B.V. All rights reserved.

In the present study the formation of lithium cobaltite using a modified Pechini aqueous sol-gel process was investigated. The gelling processes in the lithium-cobalt-citric acid system in 1.1:1:1 molar ratio was performed at 80 A degrees C using aqueous solutions of 0.25 mol/dm(3) of Co(NO3)(2)center dot 6H(2)O with Li(NO3)center dot 6H(2)O or Co(CH3COO)(2)center dot 6H(2)O with Li(CH3COO)center dot 2H(2)O, respectively. The study of the mechanism of gelling of transition metal ion Co(II) in aqueous medium in the presence of lithium ions and citric acid as chelating agents was approached using mainly UV-Vis and FTIR spectroscopic methods. The UV-Vis spectroscopy indicated that the Co(II) ions are in a tetragonal distorted geometry characteristic to a D-4h group symmetry in the solutions in the early steps of the gels formation. After gelling at 80 A degrees C it was observed that the symmetry of the Co(II) ions becomes octahedral (O-h). From the FTIR spectra based on the frequency separation between the antisymmetric stretching nu(as)(COO-) and symmetric stretching nu(sym)(COO-) vibrations, it was identified that the carboxylic groups are bond as a bridging ligands. Using X-ray photoelectron spectroscopy it was identified that the cobalt is present in both final gels as Co(II) ions and the citrate ions are covalently bonded to the cobalt ions. The thermogravimetric/differential thermal analysis showed the thermal stability of the studied gels is higher in the low temperature range for the gels prepared using acetates. Based on the thermal analysis the Li-Co-CA gels were calcinated at 700 A degrees C for 6 h and for each gel a monophasic LiCoO2 was obtained.

Both Spark Plasma Sintering (SPS) and conventional sintering were applied to obtain bulks of ledeburitic highly alloyed steels for tools fabrication. Powder mixtures of the component elements, of com-pounds or of powders obtained through ball milling of the chips resulting from the processing of parts from steels of interest were used. When compared with traditional technologies (casting and plastic deformation), SPS and the use of milled chips resulted in the formation of microstructures with a high degree of distribution homogeneity and dimensional uniformity of the carbides. As is well known, the improvement of these param-eters leads to the maximization of the functional properties of tools.

CuFe2-xCrxO4 spinel (0 <= x <= 2) powders were synthesized by a soft chemistry method-the gluconate multimetallic complex precursor route. The complex precursors were characterized by elemental chemical analysis, infrared (IR) and ultraviolet visible (UV-vis) spectroscopy, thermal analysis and Mossbauer spectroscopy. The oxide powders were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), IR, Raman and Mossbauer spectroscopy. It was shown that the structure, morphology and magnetic properties of the obtained spinel powders depend on the concentration of Cr3+ ion. The XRD of the chromium substituted copper ferrite powders calcined at 700 degrees C/1 h indicated the formation of a cubic spinel type structure for x=0.5, 1.0 and a tetragonal structure for x=0, 0.2, 2. The crystallite size ranged from 19 nm to 39 mm. The Mossbauer spectroscopy revealed the site occupancy of iron ions, relative abundance and internal hyperfine magnetic fields in both tetrahedral and cubic CuFe2-xCrxO4 spinels. (C) 2014 Elsevier Ltd and Techna Group S.r.l. All rights reserved.

A series of niobium-modified aluminum hydroxide fluorides (denoted Nb@AIF(3)), prepared via a fluorolytic sol gel synthesis was investigated for the catalytic one-pot conversion of cellulose to lactic acid. The structure of the new acid catalysts is the result of the dispersion of niobium fluoride in an aluminum hydroxide fluoride matrix. The calcination of the catalysts at a relatively low temperature (350 degrees C) stabilized this structure. Catalytic performances in terms of lactic acid yields are directly correlated with the niobium content.

A rapid high sensitive method for determining the Faraday rotation of optical glasses is proposed. Starting from an experimental setup based on a Faraday rod coupled to a lock-in amplifier in the detection chain, two methodologies were developed for providing reliable results on samples presenting low and large Faraday rotations. The proposed methodologies were critically discussed and compared, via results obtained in transmission geometry, on a new series of aluminophosphate glasses with or without rare-earth doping ions. An example on how the method can be used for a rapid examination of the optical homogeneity of the sample with respect to magneto-optical effects is also provided. (C) 2015 AIP Publishing LLC.