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Nitrogen Flow (nitrogen + flow)
Selected AbstractsPreparation and properties of polyethoxysilsesquioxane-C60 hybridsJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 15 2007Takahiro Gunji Abstract Free-standing films of C60 -polyethoxysiloxane hybrids were prepared, and their optical limiting properties were evaluated. Triethoxysilylated C60, with a formula of H3C60[Si(OEt)3]3, was synthesized by the hydrolysilylation of C60 with triethoxysilane in the presence of platinum catalyst. C60 -polyethoxysiloxanes were prepared by a cohydrolytic polycondensation of triethoxysilylated C60 with tetraethoxysilane in a molar ratio of Si/C60 = 10,1000 under nitrogen flow. The molecular weight of C60 -polyethoxysiloxane increased with a decrease of Si/C60. Transparent and flexible free-standing films were prepared by aging an ethanol solution of C60 -polyethoxysiloxane at 80 °C for 6,8 days. The mechanical strength and Young's modulus increased with a decrease in Si/C60. These free-standing films showed an optical limiting property, for which the threshold value decreased from 1163 mJ/cm2 (Si/C60 = 1000) to 130 mJ/cm2 (Si/C60 = 10) with a decrease of Si/C60. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3273,3279, 2007 [source] Polycaprolactone- b -Poly(ethylene oxide) Biocompatible Micelles as Drug Delivery Nanocarriers: Dynamic Light Scattering and Fluorescence ExperimentsMACROMOLECULAR SYMPOSIA, Issue 1 2005Cristiano Giacomelli Abstract Summary: Dynamic light scattering (DLS) and fluorescence experiments were carried out to study PCL44 - b -PEO114 biocompatible micelles used as nanocarriers in drug delivery. Micelles prepared by a simple procedure (THF removal under nitrogen flow) exhibited a narrow size distribution with an average diameter of 100 nm. For micelles containing a hydrophobic model compound (pyrene) within the PCL core, a smaller average micellar size of 80 nm was observed, with a simultaneous broadening in the size distribution profile. In parallel to DLS results, fluorescence experiments showed evidence of pyrene encapsulation, and that the onset of the micellization process occurs at approximately 10/90 (v/v) THF/water mixtures in the case of PCL44 - b -PEO114 polymer. [source] High-output-power AlGaN/GaN ultraviolet-light-emitting diodes by activation of Mg-doped p-type AlGaN in oxygen ambientPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 6 2010Kengo Nagata Abstract We demonstrated activation annealing of Mg-doped p-type Al0.17Ga0.83N in different gases. The hole concentration of Al0.17Ga0.83N annealed in oxygen is higher than that annealed in nitrogen or air. A hole concentration of 1.3,×,1016,cm,3 at room temperature was achieved by annealing in oxygen flow at 900,°C. Secondary ion mass spectroscopy shows that hydrogen dissociation from Mg-doped Al0.17Ga0.83N is found to be enhanced by annealing in a flow of oxygen, compared with annealing in a flow of nitrogen. We confirmed the effect of activation annealing in oxygen flow on the performance of UV light-emitting diode (LED). At a DC current of 100,mA, the output power of the LED annealed in oxygen flow at 900,°C is four times higher than that of the LED annealed in nitrogen flow at 800,°C. [source] Post-annealing effect upon phosphorus-doped ZnTe homoepitaxial layers grown by MOVPEPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 5 2007Katsuhiko Saito Abstract The effect of post-annealing treatment upon the photoluminescence (PL) spectra of phosphorus-doped ZnTe homoepitaxial layers grown by metalorganic vapour phase epitaxy using tris-dimethylaminophosphorus (TDMAP) has been investigated. PL properties at 4 K of the layers are dramatically improved by the post-annealing in nitrogen flow, i.e. donor,acceptor pair emission vanishes and instead free-to-bound transition emission (FB) and broadened acceptor-related excitonic emission (Ia) appear. PL intensity at room temperature is enhanced remarkably by the treatment. While the post-annealing treatment in hydrogen flow also gives an increase in PL intensity at room temperature of the layer, PL spectrum at 4 K is almost unchanged. The intensity ratio of FB to broadened Ia for the layer after post-annealing treatment in nitrogen flow increases and the broadened Ia shifts towards longer wavelength side with increasing TDMAP transport rate. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Effect of growth conditions on grown-in defect formation and luminescence efficiency in Ga(In)NP epilayers grown by molecular-beam epitaxyPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 2 2008D. Dagnelund Abstract A detailed study of the impact of different growth conditions (i.e. ion bombardment, nitrogen flow and In content) on the defect formation in Ga(In)NP epilayers grown on GaP substrates by solid-source molecular beam epitaxy is performed. Reduced nitrogen ion bombardment during the growth is shown to significantly reduce formation of defects acting as competing recombination centers, such as a Ga interstitial defect and other unidentified defects revealed by optically detected magnetic resonance. Further, high nitrogen flow is found to be even more effective than the ion bombardment in introducing the defects. The incorporation of In by 5.1% is, on the other hand, found not to affect the introduction of defects. The results provide a useful insight into the formation mechanism of the defects that will hopefully shed light on a control of the defect introduction in the alloys by optimizing growth conditions. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Crystallization of the pneumococcal autolysin LytC: in-house phasing using novel lanthanide complexesACTA CRYSTALLOGRAPHICA SECTION F (ELECTRONIC), Issue 4 2010Inmaculada Pérez-Dorado LytC, one of the major autolysins from the human pathogen Streptococcus pneumoniae, has been crystallized as needles by the hanging-drop technique using 10%(w/v) PEG 3350 as precipitant and 10,mM HEPES pH 7.5. LytC crystals were quickly soaked in mother liquor containing 2,mM of the complex Gd-HPDO3A to produce derivatized crystals (LytCGd-HPDO3A). Both native LytC and isomorphous LytCGd-HPDO3A crystals were flash-cooled in a nitrogen flow at 120,K prior to X-ray data collection using an in-house Enraf,Nonius rotating-anode generator (, = 1.5418,Å) and a MAR345 imaging-plate detector. In both cases, good-quality diffraction patterns were obtained at high resolution. LytCGd-HPDO3A crystals allowed the collection of a SAD X-ray data set to 2.6,Å resolution indexed in terms of a P21 monoclinic unit cell with parameters a = 59.37, b = 67.16, c = 78.85,Å, , = 105.69°. The anomalous Patterson map allowed the identification of one heavy-atom binding site, which was sufficient for the calculation of an interpretable anomalous map at 2.6,Å resolution. [source] | |||||||||||||