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991.
992.
Chaoying Wan Feng Zhao Xujin Bao Bala Kandasubramanian Matt Duggan 《Journal of Polymer Science.Polymer Physics》2009,47(2):121-129
Polyamide 12/Trisilanolphenyl‐POSS (PA 12/POSS) composites were prepared via melt‐compounding. The effect of polyhedral oligomeric silsesquioxane (POSS) on crystalline structure and crystalline transition of PA 12 was investigated by wide‐angle X‐ray diffraction (WAXD) and real time fourier transform infrared spectroscopy (FTIR). WAXD results indicated that PA 12 crystallized into γ‐form as slowly cooling from melt and the presence of POSS did not influence the crystalline structure of PA 12. Both PA 12 and PA 12/POSS composites underwent Brill transitions when they were heated from room temperature to melt point. Real time FTIR patterns showed that an absorption band at 697 cm?1 ascribed to Amide V (α) mode was emerged along with the disappearance of Amide VI (γ) band at 628 cm?1 with the increase of the temperature for PA 12 and PA 12/POSS composites, which suggested that the γ‐form crystalline has transformed into α form. The Brill bands were identified and the transformed mechanism was discussed based on the real FTIR results. The addition of POSS enhanced the tensile strength and thermal stability of PA 12. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 121–129, 2009 相似文献
993.
V. S. Burakov N. A. Savastenko N. V. Tarasenko E. A. Nevar 《Journal of Applied Spectroscopy》2008,75(3):394-401
Composite copper-containing carbon nanosized structures were synthesized in the plasma of a pulsed electrical discharge, initiated
between two graphite electrodes in an aqueous copper chloride solution. We studied the effect of laser radiation on the morphology
of the nanoparticles formed, whose properties we studied by optical absorption spectroscopy and transmission electron microscopy.
We discuss the mechanisms for nanoparticle formation in a discharge submerged in a liquid, and the possibilities for laser-induced
modification of the nanoparticles. We estimated the temperature of the nanoparticles when exposed to laser radiation pulses.
__________
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 75, No. 3, pp. 372–378, May–June, 2008. 相似文献
994.
Robert Rotzoll Philipp Vana 《Journal of polymer science. Part A, Polymer chemistry》2008,46(23):7656-7666
Reversible addition‐fragmentation chain transfer (RAFT) polymerization was used to produce poly(methyl acrylate) (pMA) loops grafted onto silica nanoparticles using doubly anchored bifunctional RAFT agents 1,4‐bis(3′‐trimethoxysilylpropyltrithiocarbonylmethyl)benzene (Z‐group approach) and 1,6‐bis(o,p‐2′‐trimethoxysilylethylbenzyltrithiocarbonyl)hexane (R‐group approach) as mediators. In both cases, molecular weights of the resulting surface‐confined polymer loops increased with monomer conversion, whereas the grafting density was significantly higher in the case of the R‐group supported RAFT polymerization due to mechanistic differences of the RAFT process at the surface. This result was evident from thermogravimetric analysis and supported by scanning electron microscopy. Polymer loops with molecular weights up to 53,000 g mol?1 were accessible with polydispersities of about 2.0 without and 1.5 with the addition of free RAFT agent. UV signals of the detached pMA loops measured via size exclusion chromatography were shifted to higher molecular weights compared with the corresponding RI signals, indicating branching reactions caused by the close proximity of growing radicals and polymer at the surface of the silica nanoparticles. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7656–7666, 2008 相似文献
995.
Preparation of poly(amino‐amide) particles complexed with ZnO particles using silane coupling agents
Yayoi Yoshioka 《Journal of polymer science. Part A, Polymer chemistry》2009,47(19):4908-4918
Poly(amino‐amide) particles were prepared by reacting 4,4′‐diphenyldicarbonyl chloride and 3,3′‐diaminobenzidine using a precipitation polymerization method with ultrasonic irradiation. The resulting particles had a narrow size distribution with an average diameter of 334 nm and showed excellent dispersion stability in water. The particles obtained were then modified with silane coupling agents (GPES) by reacting the amino groups of the poly(amino‐amide) particles with the epoxide rings of the GPES molecules in N,N‐dimethylformamide or N‐methylpyrrolidone using di‐n‐butyltin dilaurate as a catalyst. The amount of GPES covalently bonded to the poly(amino‐amide) particles was found to depend strongly on the reaction solvent and catalyst used. The resulting particles showed a narrow size distribution and the connections among the particles were not observed. On the other hand, the particles before and after modification showed different thermal properties and dispersion stability in water. The GPES‐modified aromatic polyamide particles were then complexed with ZnO particles with an average diameter of about 20 nm in aqueous acetic acid solution. It was found that the surface of the aromatic polyamide particles was covered with ZnO particles via hydrolysis reaction. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 4908–4918, 2009 相似文献
996.
A Novel Approach for Introducing Bio-Materials Into Cells 总被引:1,自引:0,他引:1
A novel approach was developed to introduce biological materials into cells for gene transfection and gene therapy applications. The method is based on the technique of electrospraying bio-materials into cells. A prototype apparatus was constructed for a feasibility study. The features of the gene transfector include: (1) A dual-capillary assembly to spray suspensions of biological materials. The outer capillary provided sheathing liquid that controlled the charge level on individual particles without altering the properties of suspensions. (2) An air–CO2 gas mixture was used for suppressing possible corona discharge and kept the same gas composition as those in incubators. (3) The designed chamber enabled the spray to operate at reduced pressure for increasing sprayed particle velocity. In the feasibility study, both suspensions of plasmid and plasmid-coated gold particles were used. The plasmid used was the commercially available Enhanced Green Fluorescent Protein gene. COS-1 cells were used as the target and the liquid media was evacuated immediately prior to the spraying process. Electrospraying was conducted at ambient pressure and the duration was no more than 2 min. After the spray transfection, the media was immediately replaced and the cell samples were returned to the incubator for 36 h. Transgene expression was detected by cellular fluorescence. This technology promises to have great potential for gene transfection and therapy studies. 相似文献
997.
998.
A. Srinivasan M. N. Huda A. K. Ray 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2006,39(2):227-236
Fullerene-like silicon nanostructures with twenty and twenty-four carbon
atoms on the surface of the Si60 cage by substitution, as well as
inside the cage at various orientations have been studied within the
generalized gradient approximation to density functional theory. Full
geometry optimizations have been performed without any symmetry constraints
using the Gaussian 03 suite of programs and the LANL2DZ basis set. Thus, for the
silicon atom, the Hay-Wadt pseudopotential with the associated basis set is
used for the core electrons and the valence electrons, respectively. For the
carbon atom, the Dunning/Huzinaga double zeta basis set is employed.
Electronic and geometric properties of these nanostructures are presented
and discussed in detail. Optimized silicon-carbon fullerene like
nanostructures are found to have increased stability compared to the bare
Si60 cage and the stability depends on the number and the orientation
of carbon atoms, as well as on the nature of silicon-carbon and
carbon-carbon bonding. 相似文献
999.
Composite structures have been widely concerned in the preparation of surface enhanced Raman scattering (SERS) substrates. In this paper, by solving the problem that the magnetic material was difficult to glow in magnetron sputtering, ferro-nickel (NiFe) alloy was deposited on the cicada wing (CW) and the NiFe/CW substrate was obtained. The results of sliver nanoparticles (Ag NPs) modified on the substrate were subsequently compared, and the SERS properties of the new Ag/NiFe/CW substrate were analyzed. Obviously, the intensity of SERS signals has been greatly improved after the modification of Ag NPs, and the substrate exhibits excellent reproducibility. The Ag NPs modified substrates were also applied to the detection of toxic crystal violet (CV) solution, which showed remarkable SERS activity. It has been proved that the strategy of modifying Ag NPs on the substrate to form a composite structure has great potential for improving the SERS performance of the substrate. 相似文献
1000.
Cellulose microparticles from ginkgo seed shells were treated by ultrasonic treatments within the selected output powders (150–600 W) and durations (10–60 min) to produce cellulose nanoparticles. The main aim of this study was to investigate effects of ultrasonic conditions on the interfacial property and emulsifying property of those cellulose nanoparticles. Compared to ultrasonic output powers, ultrasonic durations showed the greater influence on morphology and physical properties of cellulose nanoparticles. Atomic force microscopy revealed that noodle-like cellulose particles with 1100 nm in length gradually became the short rod-like nanoparticles with 300 nm in length with increasing of ultrasonic duration from 10 min to 60 min. Moreover, results of contact angles indicated that ultrasound could significantly improve hydrophobicity of cellulose nanoparticles. The interfacial shear rheology showed that although all cellulose nanoparticles exhibited the similar interface adsorption behavior which showed the initial lag-phase of adsorption, followed by the interface saturation, the time of this initial lag-phase was affected by ultrasonic conditions. The increase of ultrasonic duration and ultrasonic power could shorten the time of this initial lag-phase, suggesting the resulting cellulose nanoparticles easier adsorption at the O/W interface. It was probably attributed to its small size and high hydrophobicity induced by intense ultrasonic treatments. Meanwhile, the cellulose nanoparticles with small size and higher hydrophobicity exhibited the better emulsifying ability to stabilize oil-in-water emulsions due to the formation of the viscoelastic interfacial film. This study improved understanding about changes in interfacial and emulsifying properties of cellulose nanoparticles caused by ultrasonic treatments. 相似文献