Publications

The iron oxide nanoparticles were synthetized by an adapted coprecpitation method. Stuctural and morphological characterization of the obtained iron oxide nanoparticles were investigated by X-Ray Diffraction (XRD) and Transmission Electron Microscopy (TEM). Furthermore, in vitro and in vivo studies were investigated by cell viability assay and HeLa cells. For the analysis of iron oxide toxicity in vivo, several mice were treated with normal saline and iron oxide via intraperitoneal injection (IP). The XRD spectra showed the peaks associated to the spinel cubic lattice type with the lattice of 0.835 nm. By magnified TEM image, it could be observed that the samples have a uniform morphology with relatively spherical shape and nanometric size. Moreover, inverted fluorescence microscopy images of HeLa cells with normal phenotype and HeLa cells treated for 72 hourswith a suspension of gamma-Fe2O3 nanoparticles revealed the non-toxic character. The histophtological studies have demonstrated that at 72 hours after IP administration, the iron oxide nanoparticles are not accumulating in kidney and spleen, thus establishing their utility as drug delivery systems targeted to these organs.

The aim of this study was to synthetize new nanoparticles based on methyltrimethoxysilane coated hydroxyapatite (MTHAp) for lead removal in aqueous solutions. The morphological and compositional analysis of MTHAp was investigated by scanning electron microscopy (SEM) equipped with an energy dispersive X-ray spectrometer (EDS). Removal experiments of Pb2+ ions were carried out in aqueous solutions with controlled concentration of Pb2+ and at fixed pH of 5. After the removal experiment of Pb2+ ions from solutions, porous hydroxyapatite nanoparticles were transformed into PbMTHAp_5 via the adsorption of Pb2+ ions followed by a cation exchange reaction. Our results demonstrate that the porous hydroxyapatite nanoparticles can be used as an adsorbent for removing Pb2+ ions from aqueous solution.

ZnO nanofibers were obtained by calcination of electrospun Zn(Ac)(2)center dot 2H(2)O/PMMA composite fibers and characterized by X-ray diffraction, scanning electron microscopy and photoluminescence spectroscopy. The thermal treatment led to polymer burning and polycrystalline hexagonal ZnO phase formation. The average fiber diameters range between 450 and 600 nm before calcination and 200 - 300 nm after calcination. PL investigation revealed a strong dependence of ZnO fibers emission band on the calcination temperature. Furthermore, electrical contacts were fabricated by photolithography and electric characteristics were measured.

In this letter, we study the higher-order modes excited in a high-permittivity cylindrical dielectric resonator antenna (DRA), situated asymmetrically on top of a rectangular slot in the ground plane of a microstrip line. Besides the modes excited by a symmetric positioning of the DRA above the feeding slot, we identified five new modes: TEme(010), TEme(011), TEme(210), TEme(020), and TM212 respectively. The higher-order modes offer to the DRA antenna some interesting features: They have different radiation patterns for different operating modes; modes with close resonance frequency give wideband capabilities; and sometimes, when a mode has poor performance in one polarization, it is possible that another mode with close frequency can compensate it.

Finite size effects and interfacial interactions as well as their influence on the magnetic properties of nanosized systems are discussed by starting from very basic principles of magnetism. Some preparation and subsequent processing tools for a proper engineering of the properties of such magnetic nanosized systems are introduced together with specific characterization tools. A summary of the most important technological applications related to size effects and interfacial interactions, with exemplifications starting from bio-medical applications of magnetic fluids to magnetoresitive multilayers for sensor applications are also provided.

The peculiarities of vanadium and its oxides based nanocomposite structures fabrication are brought in this paper. The selected fabrication technological conditions allow creating a V2O5 based dielectric matrix in which conducting clusters are uniformly distributed. Some optical and electrical properties of such structures are presented. It was shown that the obtained layers possess high charge sensitivity.

The electroluminescence and current density versus applied voltage were measured for the OLED cell structure which contain IrQ(ppy)(2)-5Cl as emitting layer. Two parameters, emission quantum yield and charge transport behaviors, which influences the electroluminescence, were modeled mainly concerning the non-radiative rate constants, delocalization of the HOMO and LUMO states, internal reorganization energies and bandgap of IrQ(ppy)(2)-5Cl. The non-radiative constant rates were determined using the three zero-field splitting substates responsible for the phosphorescence model and shows an increasing of these rates together with a strong interaction with the polystyrene matrix. Delocalization of the HOMO and LUMO states on the quinoline ligand, together with the small reorganization energies and bandgap lowering indicates good charge transport properties for the IrQ(ppy)(2)-5Cl compound.

Alignment layers of polyvinylcarbazole (PVK) were obtained by withdrawing from different solutions in toluene onto glass plates having SiOx layers obliquely evaporated in vacuum at 82 degrees. The alignment direction of nematic liquid crystal molecules with cyan-end group imposed by bare SiOx layers is changed when these layers are coated with PVK; the same happens with over layers of polyvinylimidazole or of polyvinylcinnamate. The effect is inhibited by doping PVK with fullerene C60 (0.1%), when the liquid crystal orientation specific for bare SiOx obliquely evaporated substrates is obtained. Other nematic (with methoxy-end group) does not show change of the orientation properties by covering the SiOx obliquely deposited layers with the mentioned polymer over layers.

The aim of this article is in the first place to familiarize the readers with barrier-cluster-heating model of the non-crystalline semiconductors, then briefly and digestedly present some results achieved by physical phenomena explanation in non-crystalline semiconductors within the frame of this model. The barrier-cluster-heating model of disordered semiconductor gives new view on photoluminescence in disordered semiconductors, too. This model enables to explain Stokes shift, Street's empirical law, fatigue effect, PLE-characteristic, electric field influence on photoluminescence, and some other physical phenomena in disordered semiconductors, including the photoinduced structural changes.

GeSi-based nanostructures show unique properties which make them suitable for integrated circuit technology. The strong interest is to enhance their electronic properties in order to improve the device performance. In order to obtain fundamental knowledge on the electrical transport taking place in GeSi nanostructures we have investigated the effects of different microstructures on the electrical behavior of GeSi nanostructured films, by modifying the annealing conditions. We manufactured GeSi nanostructured films with equiatomic composition and different structures by co-sputtering followed by adequate annealing under different temperatures. For determining the electrical behavior we performed and modeled current-temperature I - T characteristics taking into account the films structures. We found that the electrical behavior changes with the film structure by evidencing a transition in conduction mechanism. In films that are almost crystallized, being formed of small GeSi nanocrystals separated by thin amorphous regions, the I - T dependence at low temperature is due to thermally activated tunneling of carriers between neighboring nanocrystals. In contrast, in the completely crystallized films with big GeSi nanocrystals and crystallized borders between them, the electrical behavior is a typical polycrystalline one. Our findings help to clarify the conduction mechanisms taking place in GeSi nanostructures and to provide a route to electronic devices with high performance based on these materials.