Publications

New nanometric systems were produced by using specific parameters of the laser pyrolysis process. Relevant results related to the magnetic behavior of the samples were obtained via SQUID magnetometry and Mossbauer spectroscopy, the data being corroborated with those previously obtained from X-ray diffraction, transmission electron microscopy and energy dispersive X-ray spectroscopy. The formed nanocomposites contain iron carbides, iron oxides and metallic iron nanoparticles which relative content and average size depend strongly on experimental specific parameters of the pyrolysis process. The magnetic properties and the local interaction mechanisms were explained by adequate magnetic relaxation and static models. (C) 2013 Elsevier B.V. All rights reserved.

We report new photoluminescence (PL) data generated by pulsed optical excitation on the composites achieved by a mechanico-chemical reaction between ZnS in the cubic (c) and wurtzite (w) phases and polyaniline-emeraldine base (PANI-EB). Under continuous and pulsed optical excitation, powders of the (w)ZnS and (w)ZnS/PANI-EB composites display PL with different spectral compositions. Contrary to expectations, the (c)ZnS and the (c)ZnS/PANI-EB composite displayed weak PL and decay time in the range of nanoseconds. This results from the great involvement of the surface states in nanometric powders which creates efficient channels for the non-radiative recombination of the carriers. (C) 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

The synthesis of IrQ(ppy)(2)-5Cl has the advantage of a dual phosphorescence (green and red) which comes from the two ligands, phenylpyridine and quinoline. Their spectroscopic properties evidences the absorption range between 350 nm to 700 nm which is composed from the singlet and triplet states, as a result of hybridizations between Ir and the two ligands, the first one being at 625 nm. The first low energy state comes from the quinoline ligand and is responsible for the red phosphorescence at 660 nm, as results from the Density Functional Theory (DFT) analysis. The hybridization between Ir 5d orbitals and pi ligand orbitals shows strong metallic character with phenylpyridine orbitals (66% and 43%) and weak metallic character with quinoline ligand (16.8%). This fact suggests weak phosphorescence intensity in the emission spectra. Population analysis of each metallic orbital shows a small charge delocalization on the quinoline ligand for the first molecular orbital and a strong delocalization on the phenylpyridine ligands. Solvation effects induce a tuning process for the phosphorescence by changing of the matrix of the organometallic compounds which can be adjusted by the strength of intermolecular dipole-dipole interactions, using a doped guest-host molecular organic thin film system.

Barium titanate-substituted bismuth titanate ((Bi0.5Na0.5)(0.92)Ba0.08TiO3, BNT-BT0.08) nanotubes were fabricated using sol-gel chemistry, spin casting, and a porous polycarbonate membrane template. The structure and morphology of the tubes have been investigated by scanning electron microscopy and transmission electron microscopy. The diameter and length of these tubes were about 650 nm and 20 mu m, respectively, and their wall thickness was about 50 nm. The tubes were polycrystalline with average grain size of similar to 40 nm. The BNT-BT0.08 nanotubes exhibited ferroelectric behavior as evidenced by saturated piezoresponse hysteresis loops and phase switching. BNT-BT0.08 piezoelectric nanotubes promise novel device architectures and enhanced electric properties.

The results of the studies of thin layer structures based on chalcogenide glassy semiconductors (CGS) of As-Se-S system fabrication are presented in the given paper. The possibility of of As-Se-S system thin films obtaining with the given electro-physical parameters, was shown.

[(Bi0.5Na0.5)TiO3](0.92)-[BaTiO3](0.08) lead free piezoelectric materials were prepared by the pyrosol method. The as-obtained powder shows spherical grains of various sizes, composed of crystallites of about 10 nm. NBT-BT0.08 ceramic obtained at 700 degrees C show rhombohedral NBT as the main phase and traces of hexagonal Bi2O3 as secondary phase. The ceramics prepared from this powder and sintered at 1000 and 1100 degrees C are single phase with good dielectric and ferroelectric properties. (C) 2013 Elsevier Ltd and Techna Group S.r.l. All rights reserved.