National Institute Of Materials Physics - Romania

Thick slices mechanically polished cut from a pure benzil ingot grown from melt in a modified Bridgman-Stockbarger configuration were irradiated with Ni ions having a specific energy of 11.4 MeV/u at different fluences. The effect of radiation on the properties of bulk benzil has been investigated. The chemical structure was not substantially affected as shown by infrared spectrum. The changes induced on the disorder degree have been evaluated from the Urbach law and X Ray Diffraction measurements. The morphology and surface topography have been analyzed emphasising a decrease in the size of granules and an increase in the surface roughness by irradiation. No effect of irradiation on the photoluminescence emission and optical nonlinear properties has been evidenced. These results recommend benzil as candidate for applications in space technology.

In the last decades, the study of magnetic fluids with different biomedical applications such as targeted delivery of a chemotherapeutic solution to the tumor site has been of high interest. For this purpose, ultrasonic and antimicrobial studies were used to characterize the aqueous solutions based on maghemite nanoparticles. The maghemite (-Fe2O3) and dextran-coated maghemite nanoparticles (DMNp) were synthesized by coprecipitation method. The spherical shape of the nanoparticles and uniform size with an average diameter around 9.5 +/- 0.5nm for -Fe2O3 were observed in transmission electron microscopy micrographs. Dynamic light scattering was used to determine the hydrodynamic size of -Fe2O3 nanoparticles and DMNp in suspensions. The hydrodynamic diameter obtained of -Fe2O3 and DMNp was 17 and 21nm, respectively. Moreover, a noninvasive method based on ultrasounds was used to characterize the aqueous solutions. The preliminary results showed the attainable accuracy in determining acoustic wave velocity and attenuation in various solutions. These data could be correlated with particle density and size. More than that, velocity and attenuation can be used as characteristic parameters of a given solution. A finite element model of the dispersed particles, correlated with measured velocity, allowed to solve for the elastic properties of the particles. POLYM. ENG. SCI., 57:485-490, 2017. (c) 2017 Society of Plastics Engineers

Sm3+ doped partially disordered calcium-niobium-gallium -garnet (CNGG) and calcium-lithium-niobium-gallium -garnet (CLNGG) single crystals were grown by the Czochralski method. Spectroscopic characteristics of Sm:CNGG and Sm:CLNGG single crystals were obtained by high-resolution absorption and emission spectra and emission dynamics measurements. Partial energy levels of Sm3+ doped CNGG and CLNGG were extracted from the measured spectra. The Judd-Ofelt theory has been applied to evaluate the Omega(t)(t=2,4, 6) intensity parameters, radiative transition rates A(r) branching ratios beta, and radiative lifetime tau(r), of the fluorescent Sm3+ (4)G(5/2) level. The emission cross-sections for the (4)G(5/2)-> H-6(J) (J=5/2, 7/2, 9/2) transitions of special interest for visible laser application were obtained by the Fucht-bauer - Ladenburg equation. The interaction between Sm3+ ions is dipole-dipole type and the C-DA, microparameter for both crystals was calculated based on Inokuti-Hirayama model. (C) 2017 Elsevier B.V. All rights reserved.

This paper presents structural, morphological and preliminary ultrasonic characterizations of the -Cyclodextrin/hydroxyapatite (CD-HAp) composites synthesized by an adapted co-precipitation method. The structural and morphological properties were evaluated by Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectroscopy (EDX). The specific surface area, pore size and pore volume were determined using the methods of Brunauer-Emmett-Teller (BET) and Barrett-Joyner-Halenda (BJH), respectively. The novelty of our study consists in preliminary ultrasonic measurements conducted on CD-HAp composite, uniformly dispersed in distilled water. The benefit of this non-destructive method was to facilitate and simplify the characterization techniques of nanoparticles. Our experiments proved that the efficiency of lead ion removal by CD-HAp composites depended on the initial concentration of lead. The maximum adsorption capacity of the solid phase, for Pb2+ indicated a higher rate of removal by the CD-HAp_2. These adsorption results bring valuable insight into the beneficial contribution of our compounds, for the removal of heavy metal ions from aqueous solutions. Furthermore, in the present study, was evaluated the toxic effect of lead ions adsorbed by hydroxyapatite from contaminated water on HeLa cells.

Silver-doped hydroxyapatite (AgHAp) was prepared by co-precipitation method at room temperature. The obtained AgHAp was added in different amounts of collagen gel (AgHApC1 and AgHApC2). Afterward, the gel was lyophilized and the final AgHApC1 and AgHApC2 composite was achieved. The purity, crystallinity, and the phase composition of the AgHAp, AgHApC1, and AgHApC2 samples were evaluated by X-ray diffraction (XRD). The planes corresponding to the 2 values for hydroxyapatite were found in the three samples analyzed in agreement with the crystalline hydroxyapatite. In the Fourier transform infrared (FT-IR) spectra of AgHApC1 and AgHApC2 samples the peak characteristic to the presence of (2) phosphate mode at 472/cm was found. The peaks resulting from the (4) vibration of the P-O mode, (1) symmetric P-O stretching vibration and (3) P-O stretching vibration of PO43- were also evidenced in all the samples. The formation of agglomerated particles with uniform particle size was evidenced by scanning electron microscope (SEM). The uniform distribution of the constituent elements was evidenced by mapping analysis. Furthermore, the strong antibacterial activity of AgHAp, AgHApC1, and AgHApC2 samples against Gram-negative (Escherichia coli) and Gram-positive (Staphylococcus aureus) bacterial strains was shown. The inhibition zone increased drastically with the increase of silver concentration. POLYM. ENG. SCI., 57:537-545, 2017. (c) 2017 Society of Plastics Engineers

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)).

Comparative studies between doped conducting polymers and electrochemical deposited organometallic compounds reveals the interplay between crystalline-amorphous phases with significant contributions to the internal quantum efficiency in the OLED devices. The coexistence of the amorphous and crystalline phase in the electrodeposited film is revealed by the minor micro-crystal products which are present in the amorphous phase in thin films, while the many micro-crystals are randomly distributed in the thick films. Concerning the doped conducting polymers, the level of doping induces crystalline effects as a result of the - stacking between molecules, due to the Forester energy transfer processes in which the transfer rate is increased with decreasing of the distances between neighboring molecules. The crystallization processes change the emission properties of the active layers both for the luminance level and all over color, ranging from yellow to red in the case of IrQ(ppy)(2) compounds.

The purpose of this study was to obtain, characterize and evaluate the cytotoxicity and antimicrobial activity of coatings based on poly(3-hydroxybutyric acid-co-3-hydroxyvaleric acid) -Lysozyme (P(3HB3HV)/ Lys) and P(3HB-3HV) -Polyethylene glycol -Lysozyme (P(3HB-3HV)/PEG/Lys) spheres prepared by Matrix Assisted Pulsed Laser Evaporation (MAPLE) technique, in order to obtain functional and improved Ti-based implants. Morphological investigation of the coatings by Infrared Microscopy (IRM) and SEM revealed that the average diameter of P(3HB-3HV)/Lys spheres is around 2 mm and unlike the drop cast samples, IRM recorded on MAPLE films revealed a good distribution of monitored functional groups on the entire scanned surface. The biological evaluation of MAPLE structured surfaces revealed an improved biocompatibility with respect to osteoblasts and endothelial cells as compared with Ti substrates and an enhanced anti-biofilm effect against Gram positive (Staphylococcus aureus) and Gram negative (Pseudomonas aeruginosa) tested strains. Thus, we propose that the fabricated P(3HB-3HV)/PEG/Lys and P(3HB-3HV)/Lys microspheres may be efficiently used as a matrix for controlled local drug delivery, with practical applications in developing improved medical surfaces for the reduction of implant-associated infections. (C) 2017 Elsevier B. V. All rights reserved.

The present study is focused on the synthesis, characterization and antifungal evaluation of zinc-doped hydroxyapatite (Zn:HAp) coatings. The Zn:HAp coatings were deposited on a pure Si (Zn:HAp_Si) and Ti (Zn:HAp_Ti) substrate by a sol-gel dip coating method using a zinc-doped hydroxyapatite nanogel. The nature of the crystal phase was determined by X-ray diffraction (XRD). The crystalline phase of the prepared Zn:HAp composite was assigned to hexagonal hydroxyapatite in the P6(3/m) space group. The colloidal properties of the resulting Zn:HAp (x(Zn) = 0.1) nanogel were analyzed by Dynamic Light Scattering (DLS) and zeta potential. Scanning Electron Microscopy (SEM) was used to investigate the morphology of the zinc-doped hydroxyapatite (Zn:HAp) nanogel composite and Zn:HAp coatings. The elements Ca, P, O and Zn were found in the Zn:HAp composite. According to the EDX results, the degree of Zn substitution in the structure of Zn:HAp composite was 1.67 wt%. Moreover, the antifungal activity of Zn:HAp_Si and Zn:HAp_Ti against Candida albicans (C. albicans) was evaluated. A decrease in the number of surviving cells was not observed under dark conditions, whereas under daylight and UV light illumination a major decrease in the number of surviving cells was observed.

We investigated the evolution of the DC magnetic hysteresis curves of Nb0.89Ti0.11 alloys thermo-mechanically processed by intermediate heat treatments at 900 degrees C in vacuum and cold rolling (similar to 50% thickness reduction). Starting with a rectangular piece (similar to 0.4 mm thick) cut from the as-grown alloy, after the first thermo-mechanical treatment, the specimen exhibits over a wide temperature T interval a peak effect not far from the DC irreversibility line. With a supplemental thermo-mechanical treatment, the peak effect disappears and is substituted by a second magnetization peak ( where the characteristic fields are significantly lower) induced by pinning enhancement. The second magnetization peak was clearly seen at high temperatures only, due to the occurrence of thermo-magnetic instabilities in the low-T domain. In both cases, analysis of magnetic relaxation evidences a crossover towards plastic vortex creep accompanying the maximum in the effective critical current density. These results suggest a common nature of the observed effects, related to the disordering of the vortex system induced by pinning.