National Institute Of Materials Physics - Romania
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531. Synthetic fabrics coated with zinc oxide nanoparticles by electroless deposition: Structural characterization and wetting properties
Authors:
Frunza, L; Preda, N; Matei, E; Frunza, S; Ganea, CP; Vlaicu, AM; Diamandescu, L; Dorogan, A
Published: OCT 1 2013, JOURNAL OF POLYMER SCIENCE PART B-POLYMER PHYSICS, 51, +, DOI: 10.1002/polb.23346
Electroless deposition was successfully applied in developing crystalline particles of zinc oxide onto polyester textile materials; this deposition is here presented in comparison with other materials made from poly(lactic acid), polyamide or hemp. Structural and spectroscopic characterization of the raw and deposited samples has been performed. The structure of zinc oxide particles was that of wurtzite type as indicated by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Crystallites were 20-500 nm in diameter and up to 1 mu m in length. The grown particles cover the fibers not only on the fabric surface but in the textile depth. 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 superhydrophobic properties onto polyester fabrics, for which water contact angles exceed 150 degrees. The other functionalized samples also become more hydrophobic after deposition. Cassie-Baxter model was found suitable to describe the behavior, though the fraction of surface occupied by the water-solid interface is high enough. The electroless deposition technique applied previously for cotton fabrics was once more proven to be highly reproducible, easy scalable, and cheap, allowing a wide range of applications. (c) 2013 Wiley Periodicals, Inc.
532. Direct sintering of SiC-W composites with enhanced thermal conductivity
Authors:
Galatanu, M; Popescu, B; Enculescu, M; Tiseanu, I; Craciunescu, T; Galatanu, A
Published: OCT 2013, FUSION ENGINEERING AND DESIGN, 88, 2602, DOI: 10.1016/j.fusengdes.2013.05.036
Different types of SiC-W composites have been realized by spark plasma sintering in a single step process starting with beta SiC nanometric powder, W nanometric and micrometric sized powders, and W foils. SEM, EDX, XRD and X-ray tomography have been used to analyze the sample morphology while the thermal properties of the resulting materials have been investigated up to 1000 degrees C using a LFA thermal analyzer. The results show the possibility to produce dense W-SiC composites, with enhanced thermal conductivity using a relatively simple route. (C) 2013 Elsevier B.V. All rights reserved.
533. Antimicrobial activity of biopolymer-antibiotic thin films fabricated by advanced pulsed laser methods
Authors:
Cristescu, R; Popescu, C; Dorcioman, G; Miroiu, FM; Socol, G; Mihailescu, IN; Gittard, SD; Miller, PR; Narayan, RJ; Enculescu, M; Chrisey, DB
Published: AUG 1 2013, APPLIED SURFACE SCIENCE, 278, 213, DOI: 10.1016/j.apsusc.2013.01.062
We report on thin film deposition by matrix assisted pulsed laser evaporation (MAPLE) of two polymer-drug composite thin film systems. A pulsed KrF* excimer laser source (lambda = 248 nm, tau = 25ns, nu = 10 Hz) was used to deposit composite thin films of poly(D,L-lactide) (PDLLA) containing several gentamicin concentrations. FTIR spectroscopy was used to demonstrate that MAPLE-transferred materials exhibited chemical structures similar to those of drop cast materials. Scanning electron microscopy data indicated that MAPLE may be used to fabricate thin films of good morphological quality. The activity of PDLLA-gentamicin composite thin films against Staphylococcus aureus bacteria was demonstrated using drop testing. The influence of drug concentration on microbial viability was also assessed. Our studies indicate that polymer-drug composite thin films prepared by MAPLE may be used to impart antimicrobial activity to implants, medical devices, and other contact surfaces. (C) 2013 Elsevier B.V. All rights reserved.
534. Silicon bump arrays by near-field enhanced femtosecond laser irradiation in fluorine liquid precursors
Authors:
Ulmeanu, M; Anghel, I; Jipa, F; Filipescu, M; Enculescu, M; Zamfirescu, M
Published: AUG 1 2013, APPLIED SURFACE SCIENCE, 278, 304, DOI: 10.1016/j.apsusc.2013.01.050
A simple approach to fabricate periodic arrays of conical bumps on silicon (Si) substrate is reported. In the process, a single pulse from a 200 fs laser at 387 nm wavelength was applied on a self-assembled monolayer of 700 nm and 390 nm diameter silica spheres on a n-doped Si (1 0 0) wafer. The surface was irradiated at normal incidence by immersing the silicon substrates in a glass container filled with 1, 1, 2 trichlor-trifluorethan liquid precursors. After laser irradiation, at laser fluences in the range from 1 to 40 J/cm(2), a regular array of conical Si bumps was fabricated. The density of the Si bumps can be varied by varying the particle size diameter. The influence of the medium on the near-field interactions for both sizes silica particles layer is investigated. (C) 2013 Elsevier B.V. All rights reserved.
535. Self-assembled homojunction In2O3 transparent thin-film transistors
Authors:
Gherendi, F; Nistor, M; Antohe, S; Ion, L; Enculescu, I; Mandache, NB
Published: AUG 2013, SEMICONDUCTOR SCIENCE AND TECHNOLOGY, 28, DOI: 10.1088/0268-1242/28/8/085002
Homojunction transparent thin-film In2O3 transistors were fabricated at room temperature. Self-assembled In2O3 source-channel-drain structures were grown by pulsed electron beam deposition using a shadow mask with a 300 mu m diameter wire as an obstacle placed at similar to 100 mu m distance from the substrate for growing the channel region behind it. The film resistivity varies from similar to 7 x 10(8) Omega cm in the channel region to similar to 10(-3) Omega cm in the source-drain regions. We explain this fact by the relative depletion of the indium incorporated in the channel region of the film due to the reduced flux of ablated species arriving on the substrate behind the obstacle, leading to a relative enrichment in oxygen compared to the source and drain regions. The gate insulator is a Y2O3 film grown by RF magnetron sputtering. The transistor operates in enhanced mode. The subthreshold swing is similar to 0.26 V/decade with an on/off current ratio of 1.5 x 10(7), and the saturation channel mobility is greater than 45 cm(2) V-1 s(-1).
536. Magnetic configurations of Ni-Cu alloy nanowires obtained by the template method
Authors:
Matei, E; Enculescu, I; Toimil-Molares, ME; Leca, A; Ghica, C; Kuncser, V
Published: AUG 2013, JOURNAL OF NANOPARTICLE RESEARCH, 15, DOI: 10.1007/s11051-013-1863-3
High aspect ratio nanowires of Ni-Cu alloys have been synthesized by potentiostatic electrochemical deposition in etched ion-track membranes. The nickel-to-copper ratio in the nanowires was controlled via the deposition potential and electrochemical bath composition. We present a detailed study of nanowire properties including morphology, composition, and magnetic behavior. We report the magnetic configurations measured as function of the nanowire composition and discuss domain formation, anisotropy aspects, and local easy axis distributions.
537. Mechanisms of the Charge Transfer in IrQ(ppy)(2)-5Cl Dual-Emitter Compound
Authors:
Polosan, S; Radu, IC
Published: JUL 2013, JOURNAL OF NANOSCIENCE AND NANOTECHNOLOGY, 13, 5208, DOI: 10.1166/jnn.2013.7513
The synthesis of IrQ(ppy)(2)-5Cl has the advantage of a dual phosphorescence (green and red) which comes from the two ligands, phenylpyridine and quinoline. Their spectroscopic properties evidences the absorption range between 350 nm to 700 nm which is composed from the singlet and triplet states, as a result of hybridizations between Ir and the two ligands, the first one being at 625 nm. The first low energy state comes from the quinoline ligand and is responsible for the red phosphorescence at 660 nm, as results from the Density Functional Theory (DFT) analysis. The hybridization between Ir 5d orbitals and pi ligand orbitals shows strong metallic character with phenylpyridine orbitals (66% and 43%) and weak metallic character with quinoline ligand (16.8%). This fact suggests weak phosphorescence intensity in the emission spectra. Population analysis of each metallic orbital shows a small charge delocalization on the quinoline ligand for the first molecular orbital and a strong delocalization on the phenylpyridine ligands. Solvation effects induce a tuning process for the phosphorescence by changing of the matrix of the organometallic compounds which can be adjusted by the strength of intermolecular dipole-dipole interactions, using a doped guest-host molecular organic thin film system.
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