National Institute Of Materials Physics - Romania

Publications

5714 articles found

1891. INVESTIGATIONS OF PULSED LASER DEPOSITED TiN THIN FILMS FOR TITANIUM IMPLANTS

Authors: Popescu-Pelin, G; Craciun, D; Socol, G; Cristea, D; Floroian, L; Badea, M; Socol, M; Craciun, V

Published: 2015, ROMANIAN REPORTS IN PHYSICS, 67, 1502, DOI:

TiN thin films were deposited at room temperature on polished Ti samples by PLD. GIXRD investigations showed that films were crystalline, with grain sizes around 25 run. Simulations of XRR curves indicated that the layers were dense and only slightly rougher than Ti substrates. Nanoindentation results showed that TiN films possessed a hardness of 26.8 GPa, much harder than Ti substrate, while scratch and wear tests found that films were adherent and exhibited a low friction coefficient of 0.16. Electrochemical tests performed in SBF indicated that the coated Ti samples exhibited significantly better behavior against corrosion than bare Ti samples.

1892. Titanium dioxide layer deposited at low temperature upon polyester fabrics

Authors: Zgura, I; Frunza, S; Frunza, L; Enculescu, M; Florica, C; Ganea, CP; Negrila, CC; Diamandescu, L

Published: JUL-AUG 2015, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 17, 1063, DOI:

TiO2 deposition by sputtering or sol-gel techniques was applied onto less thermal stable polyester textiles and onto a related poly(lactic acid) material. The temperature of deposition and of the further treatment was low enough as allowed by the support nature. Structural and spectroscopic characterization of the raw and coated samples has been performed. TiO2 coated particles are amorphous as indicated by X-ray diffraction and scanning electron microscopy. Sputtered layers consist in aggregates randomly distributed on the substrate while the sol gel layers show a uniform coverage of nanoparticles having a mosaic-like structure. The morphology of the sputtered layers depends on the deposition pressure as well. The loading degree estimated on the basis of the thermogravimetric data is rather low (ca. 2%), but the fabric properties are much influenced by the deposition. Photocatalytic activity also present on the coated surfaces was evaluated in the methylene blue degradation. TiO2 layer is quite adherent as checked by an ultra-sonication method.

1893. Image molecular dipoles in surface enhanced Raman scattering

Authors: Teodorescu, CM

Published: 2015, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 17, 21314, DOI: 10.1039/c4cp05082g

The surface enhanced Raman scattering (SERS) effect is explained using the interaction of a polarized molecule with its instantaneous image dipole in a metal surface. This model explains why SERS is obtained mostly on noble metals (Au, Ag), since these metals usually have lower inherent contamination as compared with other more reactive metals; thus, molecules may be found closer to the metal surface. It is shown how stronger SERS amplifications may be obtained using nanostructured surfaces, once the excited molecules are localized in concave sites. The dependence on the fourth power of the incoming radiation electric field is obtained by taking into account the dynamics of adsorption-desorption processes of molecules. The SERS effect is maximal when the excitation frequency is red-shifted with respect to the bulk plasmon resonance. Also, the SERS amplification factor may be dictated by the polarizability of the investigated molecule, alpha, in a much more critical way than just a power law alpha(2) or even alpha(4). By comparing the dipole induced charge density with the amplitudes of plasma waves, the domain of validity of the present theory is derived to be in the low separation regime, where the distance between molecules and metal substrates is below a few nanometres. Some data from the literature are analyzed in the framework of this model, namely the distance, frequency and temperature dependence of the SERS signal, all confirming the validity of the model.

1894. Antimicrobial Activity Evaluation on Silver Doped Hydroxyapatite/Polydimethylsiloxane Composite Layer

Authors: Ciobanu, CS; Groza, A; Iconaru, SL; Popa, CL; Chapon, P; Chifiriuc, MC; Hristu, R; Stanciu, GA; Negrila, CC; Ghita, RV; Ganciu, M; Predoi, D

Published: 2015, BIOMED RESEARCH INTERNATIONAL, 2015, DOI: 10.1155/2015/926513

The goal of this study was the preparation, physicochemical characterization, and microbiological evaluation of novel hydroxyapatite doped with silver/polydimethylsiloxane (Ag:HAp-PDMS) composite layers. In the first stage, the deposition of polydimethylsiloxane (PDMS) polymer layer on commercially pure Si disks has been produced in atmospheric pressure corona discharges. Finally, the new silver doped hydroxyapatite/polydimethylsiloxane composite layer has been obtained by the thermal evaporation technique. The Ag: HAp-PDMS composite layers were characterized by various techniques, such as Scanning Electron Microscopy (SEM), Glow Discharge Optical Emission Spectroscopy (GDOES), and X-ray photoelectron spectroscopy (XPS). The antimicrobial activity of the Ag:HAp-PDMS composite layer was assessed against Candida albicans ATCC 10231 (ATCC-American Type Culture Collection) by culture based and confirmed by SEM and Confocal Laser Scanning Microscopy (CLSM) methods. This is the first study reporting the antimicrobial effect of the Ag: HAp-PDMS composite layer, which proved to be active against Candida albicans biofilm embedded cells.

1895. Anionic polymerization by an electron transfer process from a CdSe quantum dot-perylenediimide (PDI) system

Authors: Rusen, E; Mocanu, A; Nistor, LC; Hudhomme, P; Diacon, A

Published: 2015, RSC ADVANCES, 5, 28232, DOI: 10.1039/c5ra01865j

Reversible physical interactions between CdSe quantum dots (QDs) and perylenediimide (PDI) derivatives have been investigated. Original processes, dependent on the concentration of the two species, contact time, temperature and pH, were observed. The combining of the two solutions resulted in the formation of an electron transfer complex (ETC) due to the transfer of an electron from CdSe nanoparticles to PDI, followed by the formation of the final particularly stable dianion PDI2- species through another electron transfer process. The anionic species was employed for the polymerization initiation of glycidyl methacrylate (GMA). Some aspects of the anionic polymerization mechanism have been investigated.

1896. Pure and almost pure NIR emission of Tm and Tm,Yb-CeO2 under UV, X-ray and NIR up-conversion excitation: key roles of level selective antenna sensitization and charge-compensation

Authors: Avram, D; Cojocaru, B; Urda, A; Tiseanu, I; Florea, M; Tiseanu, C

Published: 2015, , DOI: 10.1039/c5cp03458b

1897. OPTICAL AND PHOTOCATALYTIC PROPERTIES OF ELECTROSPUN ZnO FIBERS

Authors: Busuioc, C; Evanghelidis, A; Enculescu, M; Enculescu, I

Published: JUL-SEP 2015, DIGEST JOURNAL OF NANOMATERIALS AND BIOSTRUCTURES, 10, 965, DOI:

ZnO nanofibers were obtained by electrospinning a solution of zinc acetate dihydrate and polyvinylpyrrolidone in N, N-dimethylformamide, followed by calcination at 500, 650 or 800 degrees C for 1 h. X-ray diffraction, selected area electron diffraction, scanning electron microscopy, transmission electron microscopy, reflectance spectroscopy and photoluminescence spectroscopy were used for the characterization of the resulting fibers. The thermally treated samples exhibit ZnO single phase with polycrystalline hexagonal structure. The morphological investigation revealed an accentuated contraction process during calcination, as well as the increase of the crystallite size and the appearance of a breaking tendency with the calcination temperature enhancement. Both UV and Visible emissions under excitation at 350 nm were showed by the optical studies, which also led to band gap values slightly lower than those reported for similar one-dimensional nanostructures. In order to assess the photocatalytic activity of ZnO fibers, the photodegradation of methylene blue in aqueous medium (10(-3) M) under UV irradiation (368 nm) was analyzed.

1898. Nanostructured Titanium Doped Iron Oxide Photoelectrodes for Water Splitting

Authors: Miclea, C; Amarande, L; Cioangher, MC; Miclea, CT; Mihailescu, M; Radu, C; Ivanov, A

Published: 2015, ROMANIAN JOURNAL OF INFORMATION SCIENCE AND TECHNOLOGY, 18, 105, DOI:

Water splitting by means of semiconducting photoelectrodes and solar light represents a promising alternative to conventional fossil fuel economy. In this process the photoactive electrode absorb sunlight directly thus initiating the photochemical reaction which create excess electrons in the conduction band of the semiconducting electrode. Titanium doped iron oxide seems to be a promising semiconducting material for photoelectrodes. Consequently, we investigated the effect of Ti doping on the structure, electrical and photoelectrochemical properties alpha-Fe2O3. The Ti doped alpha-Fe2O3 were prepared by a slightly modified mixed oxide route, consisting in a prolonged mixing of the raw materials in a high energy planetary ball mill until the particles decreased to the nanometric sizes. Optimum results were obtained for samples doped with 5 at. % titanium and sintered at 1200 degrees C. Photocurrents as high as 8.4 mA/cm(2), for illumination from a 300 W xenon lamp, were recorded for such samples. It is hoped that such photoelectrodes show promise for water splitting.

1899. Silver Azide Nanoparticles Embedded into Silica as Energetic Nano-materials

Authors: Ghica, C; Damian, R; Culita, D; Turcu, I; Ionita, P

Published: 2015, MATERIALS SCIENCE-MEDZIAGOTYRA, 21, 332, DOI: 10.5755/j01.ms.21.3.6926

Silver azide is a primary high explosive that can be initiated by different means. In this work, silver azide nanoparticles were obtained, embedded into silica, and further derivatized with biotin. TEM, DLS, and IR measurements were used to characterize the hybrid energetic nanoparticles. The hybrid nanoparticles are made from an explosive core (silver azide) and a shell (silica), to which has been attached through an organic linker a biological target vectot (biotin). These hybrid nanoparticles can be used as models to study smart energetic nano-materials

1900. Evolution of surface oxides on GaAs

Authors: Ghita, RV

Published: NOV-DEC 2015, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 17, 1709, DOI:

A real GaAs surface is covered with a relatively thick layer (a few nanometers) of native oxide. As2O3, As2O5, and Ga2O3 will form when a clean GaAs surface is exposed to air and light. It was put into evidence the presence of a Ga-As-O precursor oxide in an XPS measurement on native oxide at room temperature. An extended ARXPS study on native oxide on GaAs was performed for native oxides. The influence of thermal treatment on native oxides was put into evidence by an ARXPS study from Room temperature to 700 degrees C. In the thermal evolution of As and Ga oxide is observed the disappearance of As oxide at 400 degrees C and the Ga oxide at 700 degrees C. The spectral data in ARXPS analysis indicated the same evolution for As and Ga oxides.