National Institute Of Materials Physics - Romania

(Y0.87-xLa0.1Zr0.03Ybx)(2)O-3 (x = 0.02, 0.04, 0.05) transparent ceramics were obtained by solid-state reaction and combined sintering procedures with La2O3 and ZrO2 as sintering additives. A method based on two-step intermediate sintering in air followed by vacuum sintering was applied in order to control the densification and grain growth of the samples during the final sintering process. The results indicate that La2O3 and ZrO2 co-additives can improve the microstructure and optical properties of Yb:Y2O3 ceramics at relatively low sintering temperature. On the other hand, the addition of Zr4+ ions leads to the formation of dispersed scattering volumes in the ceramic bodies. Transmittance of 78.8% was measured for the 2.0 at% Yb:Y2O3 ceramic sample at the wavelength of 1100 nm. The spectroscopic properties of Yb:Y2O3 ceramics were investigated at room temperature. The obtained results show that the absorption cross-section at 978 nm is in the range of 2.08 x 10(-20) to 2.36 x 10(-20) cm(2), whereas the emission cross-section at 1032 nm is similar to 1.0 x 10(-20) cm(2).

The interaction of proteins with free radicals leads, among other types of damages, to the production of stable carbonyl groups, which can be used as a quantification of oxidative stress at proteins level. The aim of this study was the development of an electrochemical sensor for the detection of carbonyl groups in proteins oxidized by reactive oxygen species. Its working principle is based on the redox properties of dinitrophenylhydrazine (DNPH). BSA was used as a model protein and its oxidation achieved through Fenton reactions. Using differential pulse voltammetry at glassy carbon electrode, the electrochemical behavior of DNPH and of the native and oxidized BSA was investigated in solution. It has been shown that the hydrazine moiety of the DNPH is the electroactive center and is responsible for carbonyl complexation. Special attention was paid to the immobilization of the DNPH in order to retain its redox properties, and this was achieved on a mixed 4-styrenesulfonic acid-nafion matrix. The sensor's surface characterization and the detection of carbonyl groups in oxidized protein were performed by voltammetry, Fourier-transformed infrared spectroscopy and scanning electron microscopy while the voltammetric results were confirmed by surface plasmon resonance measurements. It has been shown that upon interaction with carbonyl groups of the oxidized protein, the oxidation peak of the hydrazine moiety of DNPH decreases as a function of incubation time and protein concentration. The sensor sensitivity was 0.015 nmol carbonyl per mg of oxidized protein and detection limits of 50 mu g oxidized BSA and 0.75 pmol carbonyls.

The electro-oxidation mechanism of free methionine and bound within different peptide sequences was investigated by voltammetry, at glassy carbon electrode, and mass spectrometry. It is proposed that the electro-oxidation of free methionine occurs in two steps, each involving the transfer of one electron and turns pH-independent from mild acid to mild alkaline electrolytes. The first oxidation reaction leads to the formation of a cation radical stabilized either through the amino group resulting in the dehydromethionine intermediate, or by interaction with a neutral methionine molecule leading to production of a dimer cationic radical. The dehydromethionine hydrolysis gave methionine sulfoxide as final oxidation product, whereas a future oxidation of methionine dimer cation radical, i.e. the second electro-oxidation step, results in a methionine dimer dication. Moreover, at high acid media, the protonated amino group influence the electro-oxidation process to take place via proton transfer mechanism. The presence of methionine sulfoxide and of the dimer cationic radical as oxidation products of methionine was confirmed by mass spectroscopy.

Composite thin coatings of conductive polymer (polyaniline grafted lignin, PANI-LIG) embedded with aminoglycoside Gentamicin sulfate (GS) or magnetite nanoparticles loaded with GS (Fe3O4@GS) were deposited by the matrix-assisted pulsed laser evaporation (MAPLE) technique. The aim was to obtain such nanostructured coatings for titanium-based biomedical surfaces, which would induce multi-functional properties to implantable devices, such as the controlled release of the therapeutically active substance under the action of a magnetic and/or electric field. Thus, the unaltered laser transfer of the initial biomaterials was reported, and the deposited thin coatings exhibited an appropriate nanostructured surface, suitable for bone-related applications. The laser processing of PANI-LIG materials had a meaningful impact on the composites' wettability, since the contact angle values corresponding to the composite laser processed materials decreased in comparison with pristine conductive polymer coatings, indicating more hydrophilic surfaces. The corrosion resistant structures exhibited significant antimicrobial activity against Escherichia coli, Staphylococcus aureus, and Candida albicans strains. In vitro cytotoxicity studies demonstrated that the PANI-LIG-modified titanium substrates can allow growth of bone-like cells. These results encourage further assessment of this type of biomaterial for their application in controlled drug release at implantation sites by external activation.

The work demonstrates growth by the Verneuil method of SrTiO3 single crystals of 30 mm in diameter. Experiments are performed under an industrial environment. Growth was for 4.75 h, i.e., within one production shift. The optimum growth conditions for which the length of the region with bubbles D is zero and the effective length EL (i.e., the crystal length of commercial value) is maximized are for the amount of SrCO3 additive of similar to 3 wt % and for H-2 outer flow rate of similar to 35 L/min. These two parameters show the strongest influence on the bubble-free growth, but other growth parameters (H-2 inner flow rate, O-2 flow rate increase, rotation speed) were also optimized. Selected crystals are characterized from the structural, microstructural, optical, and THz spectroscopy viewpoints, and they are compared with a commercial substrate and with crystals reported in the literature. This work opens the possibility for the industrial growth of large SrTiO3 single crystals and commercialization of large area substrates.

This research work is dedicated to study structural, morphological, optical and photoluminescence properties of samarium doped calcium sulfate (CaSO4) thin films after exposure to high gamma radiations. Polycrystalline doped CaSO4 thin films have been grown on glass substrates by spray pyrolysis technique and irradiated at different high gamma doses 3, 7, 15 and 40 kGy. Physical characterization of irradiated thin films has been made by X-ray diffraction, Spectrophotometer, Scanning Electron Microscope, Energy Dispersive Spectroscopy, Fluorescence Spectrometer and Thermoluminescence. The most remarkable result, as shown by structural analysis, is the increase of grain size from 52 to a maximum value of 93 nm for 15 kGy gamma dose which indicates a clear enhancement in crystal structure by gamma irradiation. Moreover, the preferred orientation has been immediately changed from (102) plan to (100) just after the first 3 kGy gamma dose. SEM micrographs of irradiated thin layers show deep modifications in surface morphology. Optical transmission spectra have shown a sharp and intense peak at 350 nm wavelength. Band gap energy has been slightly decreased from 3.9 eV before irradiation to 3.6 eV for 40 kGy. A new and strong energy level noted E r , has been emerged and created due to high gamma irradiations in addition to the principal one relative to band gap energy. Other parameters like absorption and extinction coefficients and refractive index have been determined. Thermoluminescence data show a high sensibility to gamma radiations doses which offer opportunities for dosimetry applications. These experimental results suggest the use of irradiated samarium doped calcium sulfate as optical window for space photovoltaic devices where gamma rays are abundant. These results are also helpful for researchers using CaSO4 thin films near nuclear apparatus (nuclear reactors and particle accelerators) or those interested in studying interaction between radiations and condensed matter.

Indium tin oxide (ITO) thin films were grown on nanopatterned glass substrates by the pulsed laser deposition (PLD) technique. The deposition was carried out at 1.2 J/cm(2) laser fluence, low oxygen pressure (1.5 Pa) and on unheated substrate. Arrays of periodic pillars with widths of similar to 350 nm, heights of similar to 250 nm, and separation pitches of similar to 1100 nm were fabricated on glass substrates using UV nanoimprint lithography (UV-NIL), a simple, cost-effective, and high throughput technique used to fabricate nanopatterns on large areas. In order to emphasize the influence of the periodic patterns on the properties of the nanostructured ITO films, this transparent conductive oxide (TCO) was also grown on flat glass substrates. Therefore, the structural, compositional, morphological, optical, and electrical properties of both non-patterned and patterned ITO films were investigated in a comparative manner. The energy dispersive X-ray analysis (EDX) confirms that the ITO films preserve the In2O3:SnO2 weight ratio from the solid ITO target. The SEM and atomic force microscopy (AFM) images prove that the deposited ITO films retain the pattern of the glass substrates. The optical investigations reveal that patterned ITO films present a good optical transmittance. The electrical measurements show that both the non-patterned and patterned ITO films are characterized by a low electrical resistivity (<2.8 x 10(-4)). However, an improvement in the Hall mobility was achieved in the case of the nanopatterned ITO films, evidencing the potential applications of such nanopatterned TCO films obtained by PLD in photovoltaic and light emitting devices.

Ferroelectric field effect transistors (FeFETs) based on lead zirconate titanate (PZT) ferroelectric material and amorphous-indium-gallium-zinc oxide (a-IGZO) were developed and characterized. The PZT material was processed by a sol-gel method and then used as ferroelectric gate. The a-IGZO thin films, having the role of channel semiconductor, were deposited by radio-frequency magnetron sputtering, at a temperature of similar to 50 degrees C. Characteristics of a typical field effect transistor with SiO2 gate insulator, grown on highly doped silicon, and of the PZT-based FeFET were compared. It was proven that the FeFETs had promising performances in terms of I-on/I-off ratio (i.e., 10(6)) and IDS retention behavior.

This paper proposes a novel, flexible, low cost administration patch which could be used as a non-invasive, controlled transdermal drug delivery system. The fabricated device consists in a flexible microfiber architecture heater covered with a thermoresponsive hydrogel, namely poly(N-isopropylacrylamide), as a matrix for the incorporation of active molecules. The manufacturing process consists of two main steps. First, the electrospun poly(methyl methacrylate) fiber networks are sputter coated with a thin gold layer and attached to flexible poly(ethylene terephthalate) substrates to obtain the heating platforms. Second, the heaters are encapsulated in poly(ethylene terephthalate) foils and covered with poly(N-isopropylacrylamide) hydrogel sheets. In order to illustrate the functionality of the fabricated patch, the hydrogel layer is loaded with methylene blue aqueous solution and is afterwards heated via Joule effect, by applying a voltage on the metalized fibers. The methylene blue releasing profiles of the heated patch are compared with those of the unheated one and the influence of parameters such as hydrogel composition and morphology, as well as the applied voltage values for microheating are investigated. The results indicate that the fabricated patch can be used as a drug administration instrument, while its performance can be tuned depending on the targeted application.

Zn1-x-yFexNdyO, x = 0.02 and y = 0.00-0.05 were successfully synthesized via a hydrothermal method at 200 degrees C. XRD and Mossbauer spectroscopy indicated that (Fe, Nd) codoped ZnO, calcined at 700 degrees C, 3 h in air, contains hexagonal ZnO phase as main phase and traces of ZnFe2O4; no phase containing neodymium was observed. In this study, a strong powder morphology dependence on Nd concentration and calcination temperature was evidenced by SEM. The photocatalytic properties were found to depend on the sample morphology and Nd content. Thermoluminescence signal is weak compared to the undoped ZnO and the curves shape was almost independent on the doping level and dependent on the calcination temperature and was related to the structural defects induced by the synthesis and calcination. Photoluminescence spectra showed that the green-yellow band due to the oxygen related defects, decreases by Fe and Nd-codoping. Thermo-magnetization curves measured in low applied fields and the magnetic hysteresis loops recorded in the temperature range 5-380 K, indicate two superimposed magnetic regimes, one predominant above 100 K the other below 100 K. The observed magnetic order is not directly related to the dopant Fe or Nd ions, but to different type of defects.