National Institute Of Materials Physics - Romania

Publications

5781 articles found

1951. Optical Properties of Single-Walled Carbon Nanotubes Functionalized with Poly(2,2 '-bithiophene-co-pyrene) Copolymer

Authors: Smaranda, I; Baibarac, M; Ilie, M; Matea, A; Baltog, I; Lefrant, S

Published: 2015, CURRENT ORGANIC CHEMISTRY, 19, 661, DOI: 10.2174/1385272819666150311231454

The photoluminescent (PL) properties of composites based on single-walled carbon nanotubes (SWNTs) and poly(2,2'-bithiophene-co-pyrene) (PBTh-Py), prepared by in situ chemical polymerization of the two monomers in the presence of carbon nanotubes, are reported. We demonstrate that the functionalization of SWNTs with PBTh-Py copolymer is revealed through a gradual quenching process of PL with the increase of SWNT content (semiconducting component) in the composite mass. FTIR spectroscopy indicates the existence of several steric hindrance effects that originate in the covalent functionalization of SWNTs with PBTh-Py copolymer. The film deposition of PBTh-Py copolymer and PBTh-Py/SWNTs composite onto rough Au supports induces changes in the FTIR spectrum, which originate in an adsorption mechanism caused by the preferential orientation of molecules on the metallic support. Surface-enhanced Raman scattering (SERS) spectroscopy reveals the side-wall functionalization of SWNTs with PBTh-Py copolymer by changes in the shapes, peak position and relative intensities of different Raman lines.

1952. AB INITIO INVESTIGATION OF OPTICAL PROPERTIES IN TRIANGULAR GRAPHENE - BORON NITRIDE CORE-SHELL NANOSTRUCTURES

Authors: Nila, AA; Nemnes, GA; Manolescu, A

Published: 2015, ROMANIAN JOURNAL OF PHYSICS, 60, 700, DOI:

We calculate the optical properties of atomic-sized core-shell graphene - boron nitride nanoflakes with triangular shaped cross-section using the density functional theory. The optical properties can be tuned by using different sizes and proportions of the core-shell materials. Anisotropic effects manifested in the absorption of unpolarized light with different orientations of the optical vector are pointed out.

1953. Organic-inorganic solar cell based on ZnO nanorod arrays

Authors: Sima, M; Vasile, E; Sima, M

Published: SEP-OCT 2015, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 17, 1313, DOI:

In this study, we communicate an investigation on perovskite solar cell based on ZnO nanorod array and spiro OMeTAD film as electron and hole selective contacts. It was found that large thickness or small electrical conduction of the Li doped spiro OMeTAD layer and recombination processes at the interfaces contributed to the reduced efficiency of the solar cell.

1954. GMR ON CuNiCo THIN LAYERS DEPOSITED USING TVA METHOD

Authors: Prioteasa, I; Porosnicu, C; Lungu, CP; Jepu, I; Schinteie, G; Ciupina, V; Prodan, G; Vasile, E; Dinca, P

Published: APR-JUN 2015, DIGEST JOURNAL OF NANOMATERIALS AND BIOSTRUCTURES, 10, 436, DOI:

Thermionic vacuum arc was successfully used to prepare high quality nanostructure thin films with different fields of applicability. One advantage of this deposition technique was the ability to have a controlled range of thicknesses starting from few nanometers to hundreds of nanometers. The purity of the thin films was insured by a high vacuum pressure and a lack of any kind of buffer gas inside the coating chamber. The aim of this work was to obtain significant magnetic response and to compare the MR to the structures obtained for two different granular combinatorial structures. The samples were investigated using scaning and transmision electron mycroscopy while SEM and The magnetic properties were first studied by measuring the electrical resistance behavior for a magnetic field of 0.3 T, at different values of the sample temperature and using a non-destructive optical method called Magneto-Optical Kerr Effect (MOKE). The magnetoresistive effect obtained for the studied samples varied from 0.6% to 19% in respect sample structure and temperature for a constant magnetic field.

1955. One-step preparation of nitrogen doped titanium oxide/Au/reduced graphene oxide composite thin films for photocatalytic applications

Authors: Datcu, A; Duta, L; del Pino, AP; Logofatu, C; Luculescu, C; Duta, A; Perniu, D; Gyorgy, E

Published: 2015, RSC ADVANCES, 5, 49779, DOI: 10.1039/c5ra07853a

Titanium dioxide (TiO2) and TiO2/Au/reduced graphene oxide (rGO) nanocomposite thin films were grown by ultraviolet matrix assisted pulsed laser evaporation (UV-MAPLE) in controlled O-2 or N-2 atmospheres. An UV KrF* excimer laser (lambda = 248 nm, tau(FWHM) similar to 25 ns, nu = 10 Hz) was used for the irradiation of the MAPLE targets consisting of TiO2 nanoparticles (NPs) or mixtures of TiO2 NPs, Au NPs, and graphene oxide (GO) platelets in aqueous solutions. The effect of Au and GO addition as well as nitrogen doping on the photocatalytic activity of the TiO2 thin films was investigated. The evaluation of the photocatalytic activity was performed by photodegradation of the organic methylene blue model dye pollutant under UV-visible light, "simulated sun" irradiation conditions. Our results show that the photocatalytic properties of TiO2 were significantly improved by the addition of Au NPs and rGO platelets. Nitrogen inclusion into the rGO structure further contributes to the enhancement of the TiO2/Au/rGO nanocomposites photocatalytic activity.

1956. STRAIN DRIVEN CHANGES OF DEFECT PARAMETERS IN HEAVY ION IMPLANTED Si

Authors: Palade, C; Lepadatu, AM; Slav, A; Ciurea, ML; Lazanu, S

Published: OCT-DEC 2015, DIGEST JOURNAL OF NANOMATERIALS AND BIOSTRUCTURES, 10, 1381, DOI:

We analyse the influence of the strain field on the parameters of trapping centres. The system under study is high resistivity Si implanted with Bi6+ and I6+ ions respectively, of 28 MeV kinetic energy, 3(O) off <100> axis orientation and 5x10(11) ions/cm(2) fluence. The strain field is the consequence of size and mass difference of the irradiation ions in respect to the atoms of the lattice, and the defects are produced during the slowing-down of ions, as a result of the energy transfer from the ion to Si atoms. These results are of interest for the design and manufacturing of microelectronic devices incorporating strain, particularly for quantum computers with qubits based on the interaction of electronic and nuclear spins of group-V donors in Si.

1957. Layered materials of LDH-type containing Zn ions: dielectric measurements show rotational fluctuations of water molecules

Authors: Frunza, L; Ganea, P; Zgura, I; Frunza, S; Neatu, F; Parvulescu, VI

Published: 2015, 2015 INTERNATIONAL SEMICONDUCTOR CONFERENCE (CAS), 70, DOI:

Layered double hydroxide (LDH) materials containing Zn ions were studied by broadband dielectric spectroscopy to follow up rotational molecular dynamics of confined water. One main relaxation process was observed in the experimental window; it was assigned to fluctuations of water molecules forming a strongly adsorbed thin layer upon the oxide surface. The temperature dependence of the relaxation rates has an unusual shape characterized by the presence of a maximum. Despite the characteristic parameters, this non-monotonous dependence is shown to be a rather general feature for water confined to LDHs.

1958. 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.

1959. 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.

1960. 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.