National Institute Of Materials Physics - Romania

Publications

5714 articles found

3001. Development Of Magnetic Fe@C Nanocomposites Obtained Via The Laser Pyrolysis: Structural And Disaggregation Properties

Authors: Morjan, I; Alexandrescu, R; Dumitrache, F; Fleaca, C; Birjega, R; Soare, I; Luculescu, CR; Prodan, V; Kuncser, V; Filoti, G; Xu, H; Wang, D

Published: 2010, BONSAI PROJECT SYMPOSIUM: BREAKTHROUGHS IN NANOPARTICLES FOR BIO-IMAGING, 1275, +, DOI: 10.1063/1.3505074

Fe@C) nanoparticles have been successfully synthesized using the laser pyrolysis method and variable nozzle geometries. At large nozzle diameters, XRD and SAED analysis clearly identified distinct alpha-Fe and Fe3C phases. TEM and HRTEM indicated that these Fe-based nanoparticles have an average grain size of 3.5-10.2 nm. Temperature dependent Mossbauer spectra further confirm their distinct nanophases. By using a multi-step reduction procedure, Fe@C powders can be disaggregated into stable, water soluble nanoparticles.

3002. HIGHLY TEXTURED (001) AlN NANOSTRUCTURED THIN FILMS SYNTHESIZED BY REACTIVE MAGNETRON SPUTTERING FOR SAW AND FBAR APPLICATIONS

Authors: Stan, GE; Pasuk, I; Galca, AC; Dinescu, A

Published: OCT-DEC 2010, DIGEST JOURNAL OF NANOMATERIALS AND BIOSTRUCTURES, 5, 1054, DOI:

Highly oriented (001) AlN (wurtzite type) thin films have been successfully deposited on silicon, platinized silicon and glass substrates by reactive radio-frequency magnetron sputtering at low temperature (150 degrees C). X-ray diffraction, spectroscopic ellipsometry and scanning electron microscopy techniques have been employed to asses the structural characteristics of the AlN films. We have investigated both the influence of AlN film's thickness and of the substrate nature on crystallinity. The thicker films present a better c axis alignment, a minimum orientation dispersion of 3.5. being reached for 1 mu m AlN on silicon. The micro-and macrostrain of the AlN lattice relaxes as the film thickness increases. The film deposited onto platinum has the maximum value of tensile strain along c axis. The film on glass exhibited the poorest texturing and the highest defect concentration. From an optical point of view the film deposited on Pt is the denser one and that deposited on glass is the most rarefied. One can conclude that when using a low deposition temperature and a base pressure of similar to 10(-4) Pa the increase of film thickness leads to improved AlN structure on Si or Pt supports.

3003. INFLUENCE OF PREPARATION METHOD ON STRUCTURAL PROPERTIES OF GeSiO NANOSYSTEMS

Authors: Stavarache, I; Lepadatu, AM; Teodorescu, V; Stoica, T; Pasuk, I; Stan, G; Iancu, V; Ciurea, ML

Published: 2010, 2010 INTERNATIONAL SEMICONDUCTOR CONFERENCE (CAS), VOLS 1 AND 2, 80, DOI: 10.1109/SMICND.2010.5650255

GeSiO nanosystems were obtained using two different preparation methods, sol-gel and magnetron-sputtering. Transmission electron microscopy measurements were performed to investigate the films structure. Amorphous and crystalline Ge dots embedded in amorphous silicon dioxide were observed. The Ge concentration in the GeSiO films was by Energy-dispersive X-ray spectroscopy.

3004. 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.

3005. 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.

3006. 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.

3007. 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.

3008. 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.

3009. 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.

3010. 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.