National Institute Of Materials Physics - Romania

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5781 articles found

3071. SYNTHESIS AND CHARACTERIZATION OF BIO-COMPATIBLE MAGHEMITE NANOPARTICLES

Authors: Predoi, D; Andronescu, E; Radu, M; Munteanu, MC; Dinischiotu, A

Published: JUL-SEP 2010, DIGEST JOURNAL OF NANOMATERIALS AND BIOSTRUCTURES, 5, 786, DOI:

The bio-compatible magnetic nanoparticles of maghemite were prepared by a chemical co-precipitation method and dextran was selected as the surfactant to suspend them. By transmission electron microscopy (TEM), the iron oxide nanoparticles appeared nearly spherical with an average diameter of about 8.0 +/- 1 nm. SAED pattern of iron oxide nanoparticles is indexed by a cubic gamma-Fe(2)O(3), the diffraction rings are attributed to the (220), (311), (400), (422), (511) and (440) planes, respectively. Regular fringes are clearly observed in the nanoparticle with a spacing of 0.24 nm, whigh is the (311) interplanar distance of the cubic maghemite. This is in perfect agreement with the X-Ray Diffraction (XRD) results, indicating that the nanoparticles are well crystallyzed in spite of their ultrafine sized. The attachment of the dextran on the particle surface was confirmed by Fourier Transform Infrared (FTIR) Spectroscopy. The biocompatibility of maghemite nanoparticles covered by dextran with HepG2 cells was checked by MTT test. Cell viability was > 98% when the iron concentration was 12.0 mu g iron/ml and 24.0 mu g iron/ml respectively. In conclusion, these nanoparticles presented a good biocompatibility with HepG2 cells, which was proportionally with the dilution level.

3072. Investigations of the Correlation Between the Preparation Method and the Properties of Anilinic Derivative Functionalised Polymer Thin Films for Non-Linear Optical Applications

Authors: Stanculescu, A; Socol, M; Albu, AM; Rasoga, O; Stanculescu, F; Ionita, I; Enculescu, I

Published: 2010, ADVANCED MATERIALS FORUM V, PT 1 AND 2, 636-637, +, DOI: 10.4028/www.scientific.net/MSF.636-637.798

This paper presents a study of two copolymers, maleic anhydride and methylmethacrilate/maleic anhydride and vinyl benzyl chloride, functionalised with polar chromophoric groups such as 2,4 dinitroaniline. Thin films have been prepared by vacuum evaporation and spin coating methods on silicon and glass substrates. UV-VIS, FTIR, XRD and Photoluminescence Spectroscopy have been used to comparatively investigate the effect of the preparation method on the properties of the thin films obtained with functionalized copolymer. SEM has evidenced differences in the morphologies of the layers suggesting a degradation of the polymeric chain during the evaporation process to fragments that conserve unchanged the chromophoric group. This explains the presence of two types of non-linear phenomena, the second harmonic emission and two-photon luminescence emissions for both vacuum evaporated and spin coated films.

3073. LOW POWER LASER INDUCED OPTICAL NONLINEARITIES IN ORGANIC MOLECULES

Authors: Dancus, I; Vlad, VI; Petris, A; Frunza, S; Beica, T; Zgura, I; Nicolescu, FA; Jerca, VV; Vuluga, DM

Published: 2010, ROMANIAN REPORTS IN PHYSICS, 62, 580, DOI:

Experimental demonstration of low power laser induced optical nonlinearities in two different types of specially designed materials: dye doped liquid crystals and copolymers with new pendant azobenzene moieties, is presented. Saturation of the nonlinear refractive index change is observed for some of the samples. The origin of the huge nonlinearity and its saturation in the continuous wave laser regime and at low power levels are analyzed.

3074. Radiation induced defects in Tl+-doped LiF crystals

Authors: Polosan, S; Secu, M; Logofatu, C; Somma, F; Montereali, RM; Vincenti, MA

Published: 2010, 11TH EUROPHYSICAL CONFERENCE ON DEFECTS IN INSULATING MATERIALS (EURODIM 2010), 15, DOI: 10.1088/1757-899X/15/1/012081

Tl+-doped lithium fluoride crystals exhibit very interesting properties concerning the formation of colour centres after X-rays irradiation. The presence of Tl+ ions, even in small concentrations, increases the number of traps which stabilize the H-centre aggregates. These H-centre aggregates become smaller and their number increases, inducing two sets of trapping levels. Photoluminescence measurements after subsequent thermal bleaching of the thermoluminescence peaks show a faster decreasing of the F-3(+) centres, in three steps, compared with the F-2 ones. The F-H recombination processes may induce the excitation-emission transitions of Tl+-ions.

3075. PHYSICO-CHEMICAL STUDIES OF SUCROSE THIN FILMS

Authors: Predoi, D

Published: APR-JUN 2010, DIGEST JOURNAL OF NANOMATERIALS AND BIOSTRUCTURES, 5, 377, DOI:

Sucrose is a natural osmolyte accumulated in cells of organisms as they adapt to environmental stress. In vitro sucrose increases protein stability and forces partially unfolded structures to refold. Thin films of sucrose (C12H22O11) were deposited on thin cut glass substrates by thermal evaporation technique (p similar to 10(-5) torr). Characteristics of thin films were putted into evidence by Fourier Transform Infrared Spectroscopy (FTIR), scanning electron microscopy (SEM) and differential thermal analysis and thermal gravimetric analysis (TG/DTA). The experimental results confirm a uniform deposition of an adherent layer.

3076. POLYMER-LIKE AND DIAMOND-LIKE CARBON COATINGS PREPARED BY RF-PECVD FOR BIOMEDICAL APPLICATIONS

Authors: Stan, GE; Marcov, DA; Popa, AC; Husanu, MA

Published: JUL-SEP 2010, DIGEST JOURNAL OF NANOMATERIALS AND BIOSTRUCTURES, 5, 718, DOI:

Hydrogenated amorphous carbon (a-C: H) films were grown by radio-frequency (1.78 MHz) plasma enhanced chemical vapour deposition technique onto medical grade Ti6Al4V substrates. By varying the deposition pressure (13.33 Pa and 53.33 Pa, respectively) and methane dilution (20% and 60%, respectively) several types of carbonic films were obtained, presenting different bonding structures, surface energies and morphological features reflected in their biological behaviour. FTIR, Raman, UV-Vis, XPS and AFM measurements were used for characterizing these structures. The surface energy was determined by contact angle measurements, and their thrombogenicity was tested by the activated partial thromboplastin time (aPTT) method. We have noticed that at the same values of methane in argon dilution but at different pressure values, the film structure was totally changed: soft polymer-like carbon (PLC) type at the higher pressure and hard diamond-like carbon (DLC) type at the lower pressure. Raman spectroscopy and XPS suggested that the highest sp(3) ratio (similar to 52%), was found for DLC films prepared in a 60% methane dilution in argon. It has been found that for both PLC and DLC structures the surface energy has a decreasing tendency with the methane concentration increase in the deposition atmosphere. Excellent aPTT results were obtained for the DLC-60 (18.6.+/- 0.3 min) and PLC-20 (17.4 +/- 0.5 min) structures, superior to those recorded for Ti6Al4V and PMMA commercial materials. These values recommend the prepared carbonic structures for medical applications: harder coatings (DLC) for metal prostheses (heart valves, acetabular cups etc.), while softer and flexible coatings (PLC) for the textile vessels or stents biofunctionalization.

3077. BIOGENIC PRODUCTION OF NANOPARTICLES

Authors: Popescu, M; Velea, A; Lorinczi, A

Published: OCT-DEC 2010, DIGEST JOURNAL OF NANOMATERIALS AND BIOSTRUCTURES, 5, 1040, DOI:

Nanoparticles of interest in nanotechnology (design of nanodevices) and medicine (controlled-release of drugs) can be produced both by anorganic and organic synthesis. The biogenetic production is now of high interest due to simplicity of the procedures and their versatility. Several species of bacteria and plants are able to synthesize nanoparticles or to help in the process of their production. The paper gives an overview on the biogenetic production of nanomaterials.

3078. ATOMIC STRUCTURE AND MAGNETIC PROPERTIES OF COBALT DOPED ZnO THIN FILMS PREPARED BY THE SOL-GEL METHOD

Authors: Neamtu, J; Georgescu, G; Malaeru, T; Gheorghe, NG; Costescu, RM; Jitaru, I; Ferre, J; Macovei, D; Teodorescu, CM

Published: OCT-DEC 2010, DIGEST JOURNAL OF NANOMATERIALS AND BIOSTRUCTURES, 5, 885, DOI:

The ability of a sol-gel route for the synthesis of cobalt doped ZnO (Zn 1-xCoxO, x = 0.04-0.11) films grown on Si (100) and glass substrates is investigated. A homogeneous and stable Zn (1-x) CoxO sol was prepared by dissolving zinc nitrate hexahydrate and cobalt acetate tetrahydrate in a PVP (polyvinylpyrrolidone) solution, followed by annealing at 800 degrees C. Local structure studies of the Zn1-xCoxO thin films by XANES (X-ray absorption near-edge structure) and EXAFS (extended X-ray absorption fine structure) proved the co-existence of a few amount of small metal cobalt aggregates with Co in non-stoichiometric ConOm aggregates, with n > m, and m similar to 4. Low temperature magneto-optical Kerr effect (Faraday rotation) measurements of the magnetization versus field give a direct proof of a superparamagnetic behavior of the magnetic aggregates and allowed an estimate of the number of magnetically active atoms in Co aggregates, which is close to the number of Co excess atoms inferred from XANES and EXAFS considerations: n - m similar to 3 atoms per aggregate. To this main superparamagnetic phase, a weak ferromagnetic phase with coercitive field of similar to 50 Oe is superimposed, most probably due to metal cobalt nanoclusters.

3079. Magnetic Configuration and Relaxation in Iron Based Nano-Particles: A Mossbauer Approach

Authors: Kuncser, V; Schinteie, G; Alexandrescu, R; Morjan, I; Vekas, L; Filoti, G

Published: 2010, TRENDS IN NANOPHYSICS: THEORY, EXPERIMENT AND TECHNOLOGY, 314, DOI: 10.1007/978-3-642-12070-1_13

The difficulty to stabilize a definite crystalline structure or phase, due to a large gradient of defects along the particle diameter, is unfortunately specific to particles of nanometer size. Therefore, atypical spin configurations and magnetic anisotropies as well as enhanced magnetic relaxations via thermal excitations are expected in systems of fine nano-particles. The actual work reports on various possibilities for a comprehensive characterization of the magnetic configuration and magnetic relaxation mechanisms of nano-particles, by corroborating the powerful method of Mossbauer spectroscopy with complementary magnetic and structural techniques. The capabilities of temperature and field dependent Mossbauer spectroscopy to provide valuable information about spin blocking temperatures, effective anisotropy constants, amount of uncompensated spins inside of particle and magnetic phase composition are critically discussed for both powder like systems and nano-particles dispersed in different solvents.

3080. Mossbauer measurements on SnSe(2)

Authors: Bibicu, I; Lorinczi, A; Popescu, M

Published: 2010, , DOI: 10.1117/12.881773

Tin chalcogenides SnX(2) and SnX, where X = S, Se and Te present a particularly interest for their electronic properties and applications in gas sensors. The state of tin in these materials is important for understanding of the sensing effect and improvement of the sensor performances. Mossbauer spectroscopy is a widely used technique for the analysis of the local electronic structure or chemical bonding in solids. In this paper we applied Mossbauer technique for the investigation of bulk and thin films of SnSe(2) chalcogenide. The films of SnSe2 chalcogenide were obtained by the methods: PLD ("Pulsed laser deposition") and PED ("Pulsed electron deposition"). Mossbauer measurements were performed by transmission (TMS), respectively conversion electron spectroscopy (CEMS). By CEMS spectroscopy surfaces, coatings and thin films containing Sn can be studied on substrates and to various depths up to 1000 nanometers.