National Institute Of Materials Physics - Romania

In this study, the cerium-doped hydroxyapatite (Ca10-xCex(PO4)(6)(OH)(2) with x(Ce) = 0.1, 10Ce-HAp) coatings obtained by the spin coating method were presented for the first time. The stability of the 10Ce-HAp suspension particles used in the preparation of coatings was evaluated by ultrasonic studies, transmission electron microscopy (TEM), X-ray diffraction (XRD), and scanning electron microscopy (SEM). The surface morphology of the 10Ce-HAp coating was studied by SEM and atomic force microscopy (AFM) techniques. The obtained 10Ce-HAp coatings were uniform and without cracks or unevenness. Glow discharge optical emission spectroscopy (GDOES) and X-ray photoelectron spectroscopy (XPS) were used for the investigation of fine chemical depth profiling. The antifungal properties of the HAp and 10Ce-HAp suspensions and coatings were assessed using Candida albicans ATCC 10231 (C. albicans) fungal strain. The quantitative antifungal assays demonstrated that both 10Ce-HAp suspensions and coatings exhibited strong antifungal properties and that they successfully inhibited the development and adherence of C. albicans fungal cells for all the tested time intervals. The scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM) visualization of the C. albicans fungal cells adherence to the 10Ce-HAp surface also demonstrated their strong inhibitory effects. In addition, the qualitative assays also suggested that the 10Ce-HAp coatings successfully stopped the biofilm formation.

Pottery vessels made of kaolin clay from the Roman Period (2nd, 3rd centuries CE) found in Romula (Re?ca village, Olt County, Romania) from Dacia Inferior (Malvensis) were investigated by petrographic, X-ray diffraction, X-ray fluorescence, thermal analysis, electron microscopy, and mechanical tests. Our results are compared with available data on kaolin clays and pottery vessels from other sites located along the lower course of Danube river and near the Black Sea, namely in Moesia Superior, Moesia Inferior, and Thracia. Archeological and geographical contexts are addressed. Results of our analysis suggest a local production of ceramics in Romula, by using raw materials from the north of Lower Danube, in opposition to the idea that kaolin ware was imported from the provinces south of the Danube.

The purpose of this review is to provide an overview of the available gypsum based composite including various phase change materials employed to increase the thermal energy storage capacity of building materials. A wide range of materials such as n-alkane, saturated fatty acid, fatty acid esters etc are used as phase change materials. Adding carbonaceous material (carbon nanofibers, activated nanocarbon, graphite nanosheets etc.) to augment some properties is also a common practice. In addition, there are presented the methods of obtaining the nano/macro-composites together with some thermal characteristics of the newly prepared materials.

The azathioprine (AZA) electrochemical adsorption onto the screen-printed carbon electrodes (SPCE) modified with the reduced graphene oxide (RGO) sheets in the absence and in the presence of polyaniline-emeraldine salt (PANI-ES) is reported in this work. Using cyclic voltammetry(CV), in the case of the SPCE modified with the RGO sheets non-functionalized and functionalized with PANI-ES, respectively, an irreversible process at the electrode/electrolyte interface is highlighted to take place. In the case of the SPCE modified with the non-functionalized RGO sheets(SPCE-RGO), the oxidation-reduction processes induce an up-shift of the AZA Raman lines from 856 and 1011 cm(-1) to 863 and 1020 cm(-1), respectively. These variations indicate an AZA adsorption onto the surface of the SPCE modified with the RGO sheets that takes place throughtthe imidazole and pyrimidine cycles of mercaptopurine, when the generation of the pi-pi(*) bonds between the mercaptopurine structure and hexagonal carbon cycles of RGO occurs. The electrochemical functionalization of the RGO sheets with PANI-ES is proved bythe appearance of the Raman lines at 1165, 1332-1371, 1496 and 1585 and 1616 cm(-1). The oxidation-reduction processes induced at the interface of the SPCE modified with PANI-ES functionalized RGO sheets and the electrolyte consisting into a phosphate buffer (PB) and AZA lead to thegeneration of new positive charges onto the PANI macromolecular chain and the adsorption of the drug on the working electrode surface that takes place via the pi-pi(*) bonds established between the benzene/quinoide rings of PANI and the imidazole/ purine cyclesof AZA. These results indicate that the SPCE modified with the PANI-ES functionalized RGO sheets shows potential applications in the field of sensors for AZA detection.

Looking for multifunctional materials, an assessment of the performances both as fire retardant and generator of electrically conductive surfaces for a three component mixture of graphene oxide, phosphoric acid and melamine applied on wood chipboard was performed. A simple approach was used to investigate the intumescent char formation and quantify the loss mass during vertical burning tests, in which the prepared samples were exposed for a certain time interval to a flame generated by an ethanol lamp in ambient conditions. Moreover, mass loss evolution and structural changes that occur during the burning process were more comprehensive investigated by differential thermal and thermogravimetric (DTA/TGA) techniques. By comparing the performances between the wood chipboard samples without any coverage and those covered with one or multiple component mixture, an increase of protection against the fire action was noticed when the three component mixture was used. Also, an improvement of the electrical properties was observed, after flame exposure of the samples covered with multiple layers (i.e., two and three), when the three component mixture was used. Morphological and structural investigations by microscopy (optical and electronic-SEMEDX), X-ray diffraction (XRD) and spectral (Raman, FTIR) methods are described. An assessment of market potential is also discussed.

Properties of epitaxial PbZr0.2Ti0.8O3 (PZT) films deposited on Si substrates were investigated for integration in the present CMOS technology. Polarization is downward oriented, in association with the presence of an internal electric field, and has a lower value compared to the PZT films deposited on single crystal perovskite SrTiO3 (STO) substrates (40 mu C/cm(2) versus 80 mu C/cm(2)), while the dielectric constant is larger (180 versus 120). Large value for the pyroelectric coefficient was also found, 1.22 x 10(-3)C/m(2)K, as for PZT grown on single crystal STO. The macroscopic ferroelectric and pyroelectric properties appear to be affected by the structural quality and stoichiometry of the PZT film. The changes in the electric properties are an effect of the strain gradients induced by the large difference between the thermal expansion coefficients of PZT and Si substrate, leading in turn to Pb oxidation and antisite defect formation compared to PZT films deposited on STO substrates.

Chemical polymerization of o-phenylenediamine (OPD) in the presence of poly(ethylene oxide), double-wall carbon nanotubes (DWNTs) and ferric chloride is carried out in order to obtain composites based on the poly(o-phenylenediamine)-poly(ethylene oxide) (POPD-PEO) fibres covered and interconnected with DWNTs. Vibrational and photoluminescence properties of these composite materials as well as their morphologies are shown by infrared (IR) spectroscopy, Raman scattering, photoluminescence (PL) and scanning electron microscopy (SEM). An adsorption of DWNTs onto the POPD rods surface in the absence and in the presence of. PEO is highlighted by SEM. The vibrational changes reported by Raman scattering and IR spectroscopy prove a covalent functionalization of DWNTs with the macromolecular compound POPD which is doped with FeCl4- T ions. New hydrogen bonds are generated between POPD covalently functionalized DWNTs and hydroxyl groups of PEO according to IR spectroscopic studies. The two macromolecular compounds, POPD and POPD-PEO, show a complex emission band with maxima at 572 and 566 nm, having a shoulder at 667 nm. A significant change in the profile of the PL bands of POPD and POPD-PEO is induced in the DWNTs presence. We show that DWNTs induce (i) a diminution in the POPD PL band intensity peaked between 525-600 nm simultaneous with the increase in the intensity of the PL band situated in the 600-800 nm spectral range and (ii) an enhancement process of the emission band localized in the 475-800 nm spectral range in the case of POPD-PEO.

In this work, the electrochemical polymerization of pyrrole in the presence of H3PMo12O40 onto the screen-printed carbon electrodes (SPCE) modified with double-walled carbon nanotubes (DWNTs) is reported. The influence of the pyrrole and H3PMo12O40 concentration as well as a scan rate used to recording of cyclic voltammograms that describe the electrochemical synthesis of polypyrrole (PPY) onto the DWNTs surface is assessed. Using scanning electron microscopy (SEM) we demonstrate that the electrosynthesis of PPY doped with H3PMo12O40 heteropolyanions (PPY-PMo12) results in the generation of a globular morphology. Considering the variations induced of DWNTs in the IR and Raman spectra of PPY doped with H3PMo12O40 heteropolyanions, a functionalization process of carbon nanotubes with macromolecular compound is invoked. According to SEM investigations, DWNTs allow the realization of connections between the globular structures of the macromolecular compound. The changes induced of folic acid (FA) during the oxidation-reduction processes at the interface of the DWNTs functionalized with PPY doped with H3PMo12O40 heteropolyanions (SPCE-DWNT/PPY-PMo12) with electrolyte solution are reported.

The specific roles played by both support and noble metals in light absorption, charge separation, and the formation of center dot OH and O-2(-) (ROS) are analyzed for light-triggered oxidation of phenol (Ph) over pristine and over noble metal (Ag, Au, Pt) -loaded TiO2. Experiments show that the supported noble metals act as a light visible absorber, assist the separation of photo-charges and reduction of O-2 to O-2(-). The O-2(-) oxidizes mildly Ph to oxygenated products (hydroquinone, benzoquinone, and 1,2-dihydroxibenzene). In a parallel process, center dot OH radicals, yielded by TiO2, mineralize Ph to CO2 by fast reaction sequences. Radical quenching and photo electrochemical measurements (surface photovoltage) confirm independently that the production of center dot OH and O-2(-) scale with oxidative conversion of Ph. The selectivity to CO2 and mild oxidation products is the result of the interplay between catalyst activity for center dot OH and for O-2(-) production.