National Institute Of Materials Physics - Romania

Publications

5714 articles found

2131. Luminescent liquid crystalline materials based on palladium(II) imine derivatives containing the 2-phenylpyridine core

Authors: Micutz, M; Ilis, M; Staicu, T; Dumitrascu, F; Pasuk, I; Molard, Y; Roisnel, T; Circu, V

Published: 2014, DALTON TRANSACTIONS, 43, 1161, DOI: 10.1039/c3dt52137k

In this work we report our studies concerning the synthesis and characterisation of a series of imine derivatives that incorporate the 2-phenylpyridine (2-ppy) core. These derivatives were used in the cyclo-metalating reactions of platinum(II) or palladium(II) in order to prepare several complexes with liquid crystalline properties. Depending on the starting materials used as well as the solvents employed, different metal complexes were obtained, some of them showing both liquid crystalline behaviour and luminescence properties at room temperature. It was found that, even if there are two competing coordination sites, the cyclometalation process takes place always at the 2-ppy core with (for Pt) or without (for Pd) the imine bond cleavage. We successfully showed that it is possible to prepare emissive room temperature liquid crystalline materials based on double cyclopalladated heteroleptic complexes by varying the volume fraction of the long flexible alkyl tails on the ancillary benzoylthiourea (BTU) ligands.

2132. MICROSTRUCTURE OF THE a-C: H/W LAYERS DEPOSITED BY PLASMA ASSISTED SEQUENTIAL DEPOSITION METHOD

Authors: Acsente, T; Negrea, RF; Lazea-Stoyanova, A; Nistor, LC; Dinescu, G

Published: APR-JUN 2014, DIGEST JOURNAL OF NANOMATERIALS AND BIOSTRUCTURES, 9, 450, DOI:

A study regarding the microstructure of a-C: H/W mixed materials deposited by plasma assisted sequential deposition method is presented. The deposition of layers was performed by cyclic exposing a substrate, for predefined time intervals, to two deposition processes, working in alternative sequences: Magnetron Sputtering (MS) for metal deposition and Plasma Enhanced Chemical Vapor Deposition (PECVD) for carbon deposition. During the deposition the plasma parameters were kept constant while the durations of the individual MS and PECVD steps were systematically modified. The deposited samples were investigated using both transmission and scanning electron microscopy methods. Nanocomposite structures are obtained if each metal deposition step is interrupted in the island stage of the layer formation followed by coverage with a continuous layer of carbon. Multilayer structures are obtained when the full development of a continuous metallic layer is allowed. The spatial periodicity of the multilayers can be adjusted in between tens and hundreds of nanometers by proper setting the duration of substrate exposure to plasma sources.

2133. AZO THIN FILMS SYNTHESIZED BY RF-MAGNETRON SPUTTERING: THE ROLE OF DEPOSITION POWER

Authors: Besleaga, C; Ion, L; Antohe, S

Published: 2014, ROMANIAN REPORTS IN PHYSICS, 66, 1001, DOI:

Transparent c-axis textured aluminum doped zinc oxide (AZO) films were deposited at room temperature onto glass substrates by radio-frequency magnetron sputtering. The effect of sputtering power on the properties of the AZO sputtered thin films was investigated. Our results indicated that the sputtering power has a great influence on the crystalline quality and electrical parameters of AZO films, thus being a useful tool for tuning their functional properties.

2134. Size Effects in Nanostructures Basics and Applications Preface

Authors: Kuncser, V; Miu, L

Published: 2014, SIZE EFFECTS IN NANOSTRUCTURES: BASICS AND APPLICATIONS, 205, VII, DOI:

2135. THERMAL EFFECTS PRODUCED AT CRYOGENIC TEMPERATURES IN MATERIALS USED AS BOLOMETRIC DETECTORS FOR DARK MATTER

Authors: Lazanu, I; Lazanu, S

Published: 2014, ROMANIAN REPORTS IN PHYSICS, 66, 972, DOI:

In the modern cryogenic technique the heat deposited as phonons, the ionization and/or light from scintillation signals could be used for detection. Also, the formation of defects in the lattice structure of material is possible. In the case when the ionization signal is used for detection, a bias voltage must be applied and thus the generalised Luke-Neganov effect must be considered with contributions from the energy stored in the semiconductor lattice as stable defects in the form of Frenkel pairs. In the process of interaction between the projectile particle and the target, the transient phenomena by which the energy is transferred producing ionization, heat and defects was investigated in the frame of a thermal spike model. A detailed discussion of the associated difficulties of this analysis is done and the results put in evidence the interplay between the primary energies deposited in the electronic and lattice subsystems. This process affects the effective number of defects and the energy stored, which is taken into consideration in the balance of energy conservation in Luke Neganov effect

2136. MOSSBAUER SPECTROSCOPY STUDY ON YVO4:Eu LUMINESCENT MATERIAL

Authors: Bibicu, I; Constantinescu, S; Diamandescu, L; Voiculescu, AM; Cotoi, E

Published: 2014, ROMANIAN REPORTS IN PHYSICS, 66, 1017, DOI:

The information about the local neighborhood of Eu Mossbauer isotope locating in yttrium vanadate nanoparticles was obtained by the room temperature measurements, in transmission and electron backscattering geometry. The Eu has the valence state 3+ and two different quadrupole elementary patterns can be distinguished up to around T-0 = 700 degrees C. At higher temperatures, the Mossbauer spectra consist in a single quadrupole pattern. Electron-backscattering spectra revealed a tendency to change T-0 and a higher distortion of the Eu neighborhood.

2137. Polyester fabrics coated with SiOx nanoparticles by vacuum deposition at small angle. Structural characterization and wetting properties

Authors: Frunza, L; Zgura, I; Enculescu, M; Frunza, S; Ganea, CP; Rasoga, O; Cotorobai, F; Dorogan, A

Published: JAN-FEB 2014, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 16, 181, DOI:

Vacuum deposition at small angle was successfully applied in deposition of SiOx particles onto polyester textile materials; this deposition is here presented in comparison with that upon other materials made from poly(lactic acid), polyamide or hemp. Structural and spectroscopic characterization of deposited samples has been performed and compared with that of the raw materials. The deposited particles are amorphous. Contact angle measurement by the sessile drop method, was used to study the wettability behavior of the investigated composite systems. The hierarchical roughness structure generates hydrophylic properties onto polyester fabrics and the other functionalized samples after deposition. The deposition technique was proven to be highly reproducible, easy scalable and cheap, allowing a wide range of applications.

2138. UV SENSING EFFECT IN LANGMUIR-BLODGETT COMPLEX FILMS CONTAINING A NOVEL SYNTHESIZED Fe(III) PORPHYRIN

Authors: Baschir, L; Fagadar-Cosma, E; Creanga, I; Palade, A; Lascu, A; Birdeanu, M; Savastru, D; Savu, V; Antohe, S; Velea, A; Fagadar-Cosma, G; Popescu, M; Simandan, ID

Published: APR-JUN 2014, DIGEST JOURNAL OF NANOMATERIALS AND BIOSTRUCTURES, 9, 857, DOI:

A novel structure of metalloporphyrin, namely: 5,10,15,20-tetrakis(3,4-dimethoxyphenyl)-porphyrin Fe(III) chloride, was successfully synthesized. UV sensitive structure based on barium stearate functionalized with the novel synthesized porphyrin and carbon nanotubes was obtained. A five monolayers structure was deposited from solution by Langmuir - Blodgett technique onto a ceramic substrate with interdigital platinum electrodes. The complex film shows sensitivity to UV radiation due to the fact that an electron is excited from a Fe d orbital into a porphyrin antibonding pi orbital and is moved onto the ligand that is attached, facilitating the charge separation, while the presence of SWCNT activates the transport of the charge carriers.

2139. Influence of 2,2 '-bipyridine on oxidative dissolution of iron monosulfide

Authors: Chirita, P; Badica, CE; Constantin, CA; Birsa, LM; Matei, E; Baibarac, M

Published: OCT-NOV 2014, SURFACE AND INTERFACE ANALYSIS, 46, 846, DOI: 10.1002/sia.5459

The 2,2'-bipyridine effects on iron monosulfide (FeS) oxidative dissolution rates have been examined by potentiodynamic polarization and electrochemical impedance spectroscopy. The adsorption of 2,2'-bipyridine to synthetic FeS was investigated by batch adsorption experiments, SEM, energy-dispersive X-ray analysis and Raman spectroscopy. The experiments were performed in air-saturated solutions at pH 5, 25 degrees C and an ionic strength of I = 0.004 M NaCl. Correlation between oxidative dissolution rates and 2,2'-bipyridine adsorption suggests that FeS oxidative dissolution is the result of two antagonistic processes: (i) the inhibiting adsorption of 2,2'-bipyridine on mineral surface and (ii) the promoting effect of 2,2'-bipyridine on the iron dissolution from FeS surface. Copyright (C) 2014 John Wiley & Sons, Ltd.

2140. Generation of Porous Alumina Layers in a Polydimethylsiloxane/Hydrogen Peroxide Medium on Aluminum Substrate in Corona Discharges

Authors: Groza, A; Surmeian, A; Diplasu, C; Luculescu, C; Negrila, C; Ganciu, M

Published: 2014, JOURNAL OF NANOMATERIALS, 2014, DOI: 10.1155/2014/578720

The porous alumina (Al2O3) layer obtained at the interface between polydimethylsiloxane/hydrogen peroxide medium and aluminum substrate under charged and neutral species injection produced in negative corona discharges in air at atmospheric pressure is analyzed by different methods in this paper. The scanning electron microscopy investigations showed the uniform distribution of the pores formed in the alumina layer and their columnar structures. Both energy dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS) measurements indicate that during the anodization process of the aluminum in the polydimethylsiloxane/hydrogen peroxide medium in corona discharge the incorporation of silicon in the structure of the alumina layer is possible.