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Nanoparticle Formation (nanoparticle + formation)

Distribution by Scientific Domains

Polymers and Materials Science	40%
Chemistry	40%

Selected Abstracts

Alkynyl Ethers of Glucans: Substituent Distribution in Propargyl-, Pentynyl- and Hexynyldextrans and -amyloses and Support for Silver Nanoparticle Formation,

MACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 15 2010
M. Nazir Tahir
Abstract Alkynyldextrans with a DS in the range 0.1,1.67 have been prepared as reactive intermediates for further polymer-analogous functionalisation. DS and substituent distribution were determined by GLC and GLCMS after hydrolysis and acetylation, or methanolysis and trimethylsilylation. Reactivity was in the order O-2,>,O-4,,,O-3 with pronounced differences in the distinct patterns for propargyl ethers and its higher homologous. A large deviation from a random substituent distribution was observed. Propargyldextrans were not stable during long-time storage in the solid state, while terminal pentynyl and hexynyl ethers are. Pentynyldextrans showed structure formation of various geometries. They bound silver efficiently, yielding silver nanoparticles by reduction. [source]

Kinetics of Core-Shell Nanoparticle Formation by Two-Dimensional Nuclear Magnetic Resonance

MACROMOLECULAR RAPID COMMUNICATIONS, Issue 11 2009
Alaitz Ruiz de Luzuriaga
Abstract We have studied the kinetics of polymeric nanoparticle formation for poly(styrene- block -4-vinylpyridine) [P(S- b -4-VPy)], chains in a non-selective solvent using 1,4-dibromobutane (DBB) as a cross-linker by means of different nuclear magnetic resonance (NMR) spectroscopy techniques. The kinetic process was followed using 1H, 13C, and 2-D Heteronuclear Single Quantum Correlation (HSQC) NMR experiments. The kinetic data obtained from 2-D HSQC and 1H NMR experiments were in good agreement between them, proving the reliability of the 2-D HSQC NMR technique for the in situ study of the kinetics of core-shell nanoparticle formation. A value of 1.5,×,10,5 s,1 was determined for the apparent kinetic constant of the P(S- b -4-VPy)-DBB core-shell nanoparticle formation process. [source]

Nanoparticle formation through solid-fed flame synthesis: Experiment and modeling

AICHE JOURNAL, Issue 4 2009
W. Widiyastuti
Abstract The preparation of silica nanoparticles through solid-fed flame synthesis was investigated experimentally and theoretically. Monodispersed submicrometer- and micrometer-sized silica powders were selected as solid precursors for feeding into a flame reactor. The effects of flame temperature, residence time, and precursor particle size were investigated systematically. Silica nanoparticles were formed by the nucleation, coagulation, and surface growth of the generated silica vapors due to the solid precursor evaporation. Numerical modeling was conducted to describe the mechanism of nanoparticle formation. Evaporation of the initial silica particles was considered in the modeling, accounting for its size evolution. Simultaneous mass transfer modeling due to the silica evaporation was solved in combination with a general dynamics equation solution. The modeling and experimental results were in agreement. Both results showed that the methane flow rate, carrier gas flow rate, and initial particle size influenced the effectiveness of nanoparticle formation in solid-fed flame synthesis. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source]

Nanoparticle formation of organic compounds with retained biological activity

JOURNAL OF PHARMACEUTICAL SCIENCES, Issue 6 2010
Gunilla B. Jacobson
Abstract Many pharmaceuticals are formulated as powders to aid drug delivery. A major problem is how to produce powders having high purity, controlled morphology, and retained bioactivity. We demonstrate the use of supercritical carbon dioxide as an antisolvent for meeting this need for two model drug systems, quercetin, a sparingly soluble antioxidant, and short interfering RNA (siRNA), which can silence genes. In both cases we achieve retention of bioactivity as well as a narrow particle size distribution in which the particles are free of impurities. © 2009 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 99: 2750,2755, 2010 [source]

Nanoparticle formation through solid-fed flame synthesis: Experiment and modeling

Kinetics of Core-Shell Nanoparticle Formation by Two-Dimensional Nuclear Magnetic Resonance

Augmented biosynthesis of cadmium sulfide nanoparticles by genetically engineered Escherichia coli

BIOTECHNOLOGY PROGRESS, Issue 5 2009
Yen-Lin Chen
Abstract Microorganisms can complex and sequester heavy metals, rendering them promising living factories for nanoparticle production. Glutathione (GSH) is pivotal in cadmium sulfide (CdS) nanoparticle formation in yeasts and its synthesis necessitates two enzymes: ,-glutamylcysteine synthetase (,-GCS) and glutathione synthetase (GS). Hereby, we constructed two recombinant E. coli ABLE C strains to over-express either ,-GCS or GS and found that ,-GCS over-expression resulted in inclusion body formation and impaired cell physiology, whereas GS over-expression yielded abundant soluble proteins and barely impeded cell growth. Upon exposure of the recombinant cells to cadmium chloride and sodium sulfide, GS over-expression augmented GSH synthesis and ameliorated CdS nanoparticles formation. The resultant CdS nanoparticles resembled those from the wild-type cells in size (2,5 nm) and wurtzite structures, yet differed in dispersibility and elemental composition. The maximum particle yield attained in the recombinant E. coli was ,2.5 times that attained in the wild-type cells and considerably exceeded that achieved in yeasts. These data implicated the potential of genetic engineering approach to enhancing CdS nanoparticle biosynthesis in bacteria. Additionally, E. coli -based biosynthesis offers a more energy-efficient and eco-friendly method as opposed to chemical processes requiring high temperature and toxic solvents. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2009 [source]

Dichloro-Bis(aminophosphine) Complexes of Palladium: Highly Convenient, Reliable and Extremely Active Suzuki,Miyaura Catalysts with Excellent Functional Group Tolerance

CHEMISTRY - A EUROPEAN JOURNAL, Issue 13 2010
Jeanne
Abstract Dichloro-bis(aminophosphine) complexes are stable depot forms of palladium nanoparticles and have proved to be excellent Suzuki,Miyaura catalysts. Simple modifications of the ligand (and/or the addition of water to the reaction mixture) have allowed their formation to be controlled. Dichlorobis[1-(dicyclohexylphosphanyl)piperidine]palladium (3), the most active catalyst of the investigated systems, is a highly convenient, reliable, and extremely active Suzuki catalyst with excellent functional group tolerance that enables the quantitative coupling of a wide variety of activated, nonactivated, and deactivated and/or sterically hindered functionalized and heterocyclic aryl and benzyl bromides with only a slight excess (1.1,1.2,equiv) of arylboronic acid at 80,°C in the presence of 0.2,mol,% of the catalyst in technical grade toluene in flasks open to the air. Conversions of >95,% were generally achieved within only a few minutes. The reaction protocol presented herein is universally applicable. Side-products have only rarely been detected. The catalytic activities of the aminophosphine-based systems were found to be dramatically improved compared with their phosphine analogue as a result of significantly faster palladium nanoparticle formation. The decomposition products of the catalysts are dicyclohexylphosphinate, cyclohexylphosphonate, and phosphate, which can easily be separated from the coupling products, a great advantage when compared with non-water-soluble phosphine-based systems. [source]

Comparison between laser-induced nucleation of ZnS and CdS nanocrystals directly into polymer matrices

POLYMER COMPOSITES, Issue 6 2010
Athanassia Athanassiou
The nucleation of two kinds of crystalline nanoparticles, zinc sulfide (ZnS), and cadmium sulfide (CdS), is achieved directly into specific sites of polymer matrices after their irradiation with UV laser pulses. The starting samples consist of polymers doped with precursors of Zn or Cd thiolate that are proved to decompose after the absorption of UV light, resulting into the nanoparticles formation. The growth of the crystalline nanostructures is followed throughout the irradiation of the samples with successive incident pulses, by different methods, such as transmission electron microscopy, atomic force microscopy, confocal microscopy, and X-ray diffraction. Special attention is paid to the difference of the formation pathways of the two kinds of nanoparticles studied, because the Cd thiolate precursor exhibits much higher absorption efficiency than the Zn thiolate one, at the applied UV wavelength. Indeed, CdS nanoparticles become evident after the very first incident UV pulses, whereas the formation of ZnS nanocrystals requires rather prolonged irradiation, always through a macroscopically nondestructive procedure for the polymer matrix. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers [source]