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Bulk Quantities (bulk + quantity)
Selected AbstractsAtomic Layer Deposition of UV-Absorbing ZnO Films on SiO2 and TiO2 Nanoparticles Using a Fluidized Bed Reactor,ADVANCED FUNCTIONAL MATERIALS, Issue 4 2008David M. King Atomic layer deposition (ALD) was used to apply conformal, nanothick ZnO coatings on particle substrates using a fluidized bed reactor. Diethylzinc (DEZ) and water were used as precursors at 177,°C. Observed growth rates were ca. 2.0 Å/cycle on primary particles as verified by HRTEM. ICP-AES and XPS were used to quantify Zn:substrate ratios. Layers of 6, 18, and 30 nm were deposited on 550 nm SiO2 spheres for UV blocking cosmetics particles. TiO2 nanoparticles were coated in the second part of this work by ZnO shells of 2, 5, and 10 nm thickness as novel inorganic sunscreen particles. The specific surface area of powders changed appropriately after nanothick film deposition using optimized conditions, signifying that high SA particles can be functionalized without agglomeration. The ZnO layers were polycrystalline as deposited and narrowing of the FWHM occurred upon annealing. Annealing the ZnO-TiO2 nanocomposite powder to 600,°C caused the formation of zinc titanate (Zn2TiO4) in both oxygen-rich and oxygen-deficient environments. The non-ideal surface behavior of the DEZ precursor became problematic for the much longer times required for high surface area nanoparticle processing and results in Zn-rich films at this growth temperature. In situ mass spectrometry provides process control capability to functionalize bulk quantities of nano- and ultrafine particles without significant precursor waste or process overruns. ZnO overlayers can be efficiently deposited on the surfaces of primary particles using ALD processing in a scalable fluidized bed reactor. [source] 1D Conducting Polymer Nanostructures: One-Dimensional Conducting Polymer Nanostructures: Bulk Synthesis and Applications (Adv. Mater.ADVANCED MATERIALS, Issue 14-15 200915/2009) One-dimensional conducting polymer nanostructures hold great promise for many technological applications and can be chemically synthesized in bulk quantities using either template or template-free strategies. Richard Kaner and co-workers highlight on page 1487 recent research activities in this field and present their perspectives on the main challenges and future research directions for this new class of nanomaterials. [source] One-Dimensional Conducting Polymer Nanostructures: Bulk Synthesis and ApplicationsADVANCED MATERIALS, Issue 14-15 2009Henry D. Tran Abstract This Progress Report provides a brief overview of current research activities in the field of one-dimensional (1D) conducting polymer nanostructures. The synthesis, properties, and applications of these materials are outlined with a strong emphasis on recent literature examples. Chemical methods that can produce 1D nanostructures in bulk quantities are discussed in the context of two different strategies: 1) procedures that rely on a nanoscale template or additive not inherent to the polymer and 2) those that do not. The different sub-classifications of these two strategies are delineated and the virtues and vices of each area are discussed. Following this discussion is an outline of the properties and applications of 1D conducting polymer nanostructures. This section focuses on applications in which nanostructured conducting polymers are clearly advantageous over their conventional counterparts. We conclude with our perspective on the main challenges and future research directions for this new class of nanomaterials. This Progress Report is not intended as a comprehensive review of the field, but rather a summary of select contributions that we feel will provide the reader with a strong basis for further investigation into this fast emerging field. [source] Stille Reactions with Tetraalkylstannanes and Phenyltrialkylstannanes in Low Melting Sugar-Urea-Salt MixturesADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 15 2006Giovanni Imperato Abstract The transfer of simple alkyl groups in Stille reactions usually requires special solvents (HMPA) or certain organotin reagents (stannatranes, monoorganotin halides) to be efficient. Using low-melting mixtures of sugar, urea and inorganic salt as solvent, a fast and efficient palladium-catalyzed alkyl transfer with tetraalkyltin reagents was observed. The high polarity and nucleophilic character of the solvent melt promotes the reaction. Stille biaryl synthesis using electron-poor and electron-rich aryl bromides proceeds with quantitative yields in the sugar-urea-salt melt. Catalyst loading may be reduced to 0.001 mol,% and the catalyst melt mixture remains active in several reaction cycles. Showing the same or improved performance for Stille reactions than organic solvents and allowing a very simple work up, sugar-urea-salt melts are a non-toxic and cheap alternative reaction medium available in bulk quantities for the catalytic process. [source] A mechanistic investigation into the covalent chemical derivatisation of graphite and glassy carbon surfaces using aryldiazonium saltsJOURNAL OF PHYSICAL ORGANIC CHEMISTRY, Issue 6 2008Poobalasingam Abiman Abstract Modification of carbon materials such as graphite and glassy carbon in bulk quantities using diazonium salts is developed. We used both 4-nitrobenzenediazonium tetrafluoroborate and 1-antharaquinonediazonium chloride to modify graphite and glassy carbon surfaces. Experiments were carried out in the presence and absence of hypophosphorous acid and the mechanism involved in both cases were studied using cyclic voltammetry. The observed peak potentials for both the 4-nitrophenyl and 1-anthraquinonyl modified materials were found to differ depending on whether or not the hypophosphorous acid reducing agent was used. In the absence of hypophosphorous acid the derivatisation reaction was inferred to go through a cationic intermediate, whilst in the presence of the hypophosphorous acid the mechanism likely involves either a purely radical intermediate or a mixture of radical and cationic species. Derivatisation experiments from 5 to 70°C allowed us to determine the optimum derivatisation temperature for both cases, in the presence and absence of hypophosphorous acid. Optimum temperature was 20°C for the former and 35°C for the later. Copyright © 2008 John Wiley & Sons, Ltd. [source] Production of ,-Galactosyl Epitopes via Combined Use of Two Recombinant Whole Cells Harboring UDP-Galactose 4-Epimerase and ,-1,3-GalactosyltransferaseBIOTECHNOLOGY PROGRESS, Issue 4 2000Xi Chen ,-Galactosyl epitopes (or ,-Gal, oligosaccharides with a terminal Gal,1,3Gal sequence) are a class of biologically important oligosaccharides in great demand in bulk quantities for basic and clinical studies on preventing hyperacute rejection in pig-to-primate organ xenotransplantaion. A truncated bovine ,-1,3-galactosyltransferase, the key enzyme responsible for the biosynthesis of the terminal structure of ,-Gal, was cloned and overexpressed previously. The acceptor specificity was further studied in the present paper, and lactose and galactose derivatives were found to be good acceptors. To develop a more proficient reaction process, we report herein an example of an efficient enzymatic synthesis of ,-Gal oligosaccharides catalyzed by the combination of two recombinant Escherichia coli whole cells harboring the genes of a UDP-galactose 4-epimerase and the ,-1,3-galactosyltransferase, respectively. Using lactosyl azide (LacN3) as the acceptor for the glycosyltransferase, the combined use of the two recombinant cells efficiently produced ,-Gal epitope Gal,1,3LacN3 in 60,68% yield. [source] | |||||||||||||