Publications

Recently, vanadium oxide based materials have been intensively studied due to their unique structural, optical, electrical and magnetical properties. In this work, LiZnVO(4)ceramics were obtained by the conventional solid-state reaction method or by the sol-gel technique. We report on the compositional and morphological characterization of LiZnVO4 samples, as well as on the influence of the preparation method on the photoluminescence and dielectric properties. The highest emission intensity was attained for the sol-gel LiZnVO4 powder thermally treated at 600 degrees C, while the best microwave dielectric properties (epsilon(r) similar to 7.5 and Qxf similar to 37900 GHz) were achieved for the conventional LiZnVO4 resonator sintered at 700 degrees C.

The aim of this study was to provide information about the biological properties of iron oxide nanoparticles (IO-NPs) obtained in an aqueous suspension. The IO-NPs were characterized by transmission electron microscopy (TEM). Analysis of hysteresis loops data at room temperature for magnetic IO-NPs sample indicated that the IO-NPs were superparamagnetic at room temperature. The calculated saturation magnetization for magnetic iron oxide was M-s = 18.1 emu/g. The antimicrobial activity of the obtained PMC-NPs was tested against Gram-negative (Pseudomonas aeruginosa 1397, Escherichia coli ATCC 25922), Gram-positive (Enterococcus faecalis ATCC 29212, Bacillus subtilis IC 12488) bacterial as well as fungal (Candida krusei 963) strains. The obtained results suggested that the antimicrobial activity of IO-NPs is dependent on the metallic ions concentrations and on the microbial growth state, either planktonic or adherent. The obtained IO-NPs exhibited no cytotoxic effect on HeLa cells at the active antimicrobial concentrations.

The synthesis of nanosized particles of Ag-doped hydroxyapatite with antibacterial properties is of great interest for the development of new biomedical applications.. e aim of this study was the evaluation of Ca10-xAgx(PO4)(6)(OH)(2) nanoparticles (Ag:HAp-NPs) for their antibacterial and antifungal activity. Resistance to antimicrobial agents by pathogenic bacteria has emerged in the recent years and became a major health problem. Here, we report a method for synthesizing Ag doped nanocrystalline hydroxyapatite. A silver-doped nanocrystalline hydroxyapatite was synthesized at 100 degrees C in deionised water. Also, in this paper Ag:HAp-NPs are evaluated for their antimicrobial activity against ram-positive and ram-negative bacteria and fungal strains. The specific antimicrobial activity revealed by the qualitative assay is demonstrating that our compounds are interacting differently with the microbial targets, probably due to the differences in the microbial wall structures.

Caesalpinia pulcherrima (Linn) popularly known as Peacock flower in India belongs to family Caesalpiniace. In this work, we describe environment friendly technique for green synthesis of gold nanoparticles from AuCl4 solution using the Caesalpinia pulcherrima (Peacock flower) flower extract as reducing agent. The gold nanoparticles were characterized using UV-visible spectroscopy and transmission electron microscopy (TEM). The UV- visible spectra indicate a strong Plasmon resonance that is located at similar to 450 nm. The TEM analysis shows that products have spherical morphology with size ranging between 1.0-50 nm. The study also indicates that gold nanoparticles show good antimicrobial activities when compared to the standard antibiotics.

The thermal stability above 300 K of the hole-trapped Fe3+ centers, formed by X-ray irradiation at 80 K in chlorinated SrCl2:Fe2+ crystals, has been investigated by Electron Paramagnetic Resonance. In the temperature range of 300 - 520 K, the trigonal Fe3+ center completely transforms into the cubic Fe3+ center, which further decays up to 700 K. The formation and transformation of the trigonal Fe3+ center, containing off-center Fe3+ ions, is associated with the presence and thermally activated movement of the interstitial Cl- ions, present in excess in chlorinated SrCl2:Fe2+ crystals.

In this paper we investigate the properties of two-dimensional photonic crystals (2D PhCs) with both hexagonal and square symmetry for applications in optoelectronics and telecommunication. An efficient way of manipulating the light is to make use of the defects introduced within the periodic structure, which consequently break the symmetry of the crystal, resulting in linear waveguides or resonant cavities. We calculate using finite-difference time-domain and finite-difference frequency-domain methods the properties associated with several kinds of defects, conveniently selected, performed in 2D PhCs with square and hexagonal symmetry.

Electrophoretic deposition (EPD) method is employed to obtain a thick ZnO layer on a ZnO nanorod array prepared in a hydrothermal-electrochemical process. ZnO nanorods have the role to improve the mechanical stability and adherence of ZnO layer deposited by electrophoretic technique. D149 dye is used as sensitizer for ZnO semiconductor. The thus prepared ZnO layer is used for the photoanode of dye-sensitized solar cell (DSC). Performance parameters were extracted from standard current-voltage characteristic (I-V) and charge transfer phenomena occurring at ZnO/dye/electrolyte was evaluated by electrochemical impedance spectroscopy (EIS).

Sol-gel HfO2 thin films, prepared from etoxid precursor, were deposited onto silicon wafer substrates by dipcoating. Low fluence multipulse excimer laser processing was used for sol-gel film densification. The small duration of the laser pulse heating limits the quantity of oxygen atoms arriving from the surface at the HfO2/Si interface. Laser irradiations were performed using a XeCl (308 nm) excimer laser, with a homogeneous laser beam. The nanostructure evolution of the laser irradiated films, using different laser fluences between 30 and 120 mJ/cm(2) and different number of pulses, was studied by systematic cross section transmission electron microscope (XTEM) observations. Dielectric constant measurements were performed on the sol-gel HfO2 films samples after laser annealing. The optimum laser processing conditions were found to be a laser fluence of 80 mJ/cm(2) and 5000 to 10000 laser pulses. In these conditions, uniform densified HfO2 amorphous films with a dielectric constant of about 25 were obtained.

Commercially pure titanium (CP-Ti) offers a good corrosion resistance and tissue tolerance. The interfacial phenomena between biomaterial and biological fluids depend especially on surface chemistry, energy, roughness and topography of the implant Different methods are used to modify CP-Ti surface in order to improve its bonding properties to bone tissue. Besides the mechanical approaches, chemical etching and chemical oxidation, there are also other procedures improving the biocornpatibility. One of the most important involves the deposition of a bioceramic thin layer on the metallic surface. A bioceramics frequently used is hydroxyapatite (HA), the mineral component of the bone. In this paper. the main objective was to study the effects of different surface pretreatments on adherence of hydroxyapatite layer obtained by electrochemical method. The CP-Ti substrate was used in different treated states of the surface. The applicability of the electrochemical technique is relieved by the fact that it is a very rapid method, requires relatively low temperatures, being also very versatile. The obtained coatings were studied by scanning electron microscopy (SEM) associated with EDX (Energy dispersive X-ray spectroscopy, X-ray diffraction method (XRD). The adherence of the layers was evaluated by the "pull-out" test. The quality of the coating (morphology and adhesion properties) is decisively influenced by the electrochemical parameters and also by the surface state.