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Nm Particles (nm + particle)
Selected AbstractsSelective Hydrogenation of Amides using Ruthenium/ Molybdenum CatalystsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 5 2010Graham Beamson Abstract Recyclable, heterogeneous bimetallic ruthenium/molybdenum catalysts, formed in situ from triruthenium dodecacarbonyl [Ru3(CO)12] and molybdenum hexacarbonyl [Mo(CO)6], are effective for the selective liquid phase hydrogenation of cyclohexylcarboxamide (CyCONH2) to cyclohexanemethylamine (CyCH2NH2), with no secondary or tertiary amine by-product formation. Variation of Mo:Ru composition reveals both synergistic and poisoning effects, with the optimum combination of conversion and selectivity at ca. 0.5, and total inhibition of catalysis evident at ,1. Good amide conversions are noted within the reaction condition regimes 20,100,bar hydrogen and 145,160,°C. The order of reactivity of these catalysts towards reduction of different amide functional groups is primary>tertiary,secondary. In situ HP-FT-IR spectroscopy confirms that catalyst genesis occurs during an induction period associated with decomposition of the organometallic precursors. Ex situ characterisation, using XRD, XPS and EDX-STEM, for active Mo:Ru compositions, has provided evidence for intimately mixed ca. 2.5,4,nm particles that contain metallic ruthenium, and molybdenum (in several oxidation states, including zero). [source] Ketoprofen nanoparticle gels formed by evaporative precipitation into aqueous solutionAICHE JOURNAL, Issue 7 2006Xiaoxia Chen Abstract Aqueous nanoparticle gels of a poorly-water soluble drug, ketoprofen, were produced by evaporative precipitation into aqueous solution (EPAS). Liquid droplets of surfactant stabilized ketoprofen containing residual solvent were dispersed in water from 60 to 90°C below the melting point of pure ketoprofen. The carboxylic acid group in ketoprofen dissociates in pure water, providing electrostatic stabilization of the droplets to complement steric stabilization. Stable amorphous ketoprofen particles with a mean size of 135 nm, measured by dynamic light scattering, were formed with only 0.1% w/v poloxamer 407, resulting in an exceptionally high drug-to-surfactant ratio of 10:1. For 5% w/v poloxamer 407, interactions with ketoprofen produced a bluish, transparent gel composed of ,50 nm particles. In 2 min, 98% of the ketoprofen in the gel nanoparticles dissolved. The favorable interactions between the ketoprofen and poloxamer 407, along with the electrostatic and steric stabilization, lead to gelation, which further stabilizes the unusually small particles. The rapidly dissolving wet gels with extremely small particle sizes, one month stability, and relatively low viscosities, are of interest in transdermal and parenteral delivery; furthermore, the gels may be dried for oral delivery. © 2006 American Institute of Chemical Engineers AIChE J, 2006 [source] Amphiphilic PEG/alkyl-grafted comb polylactidesJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 22 2007Xuwei Jiang Abstract Amphiphilic polylactides (PLAs) with well-defined architectures were synthesized by ring-opening polymerization of AB monomers (glycolides) substituted with both a long chain alkyl group and a triethylene glycol segment terminated in either a methyl or benzyl group. The resulting amphiphilic PLAs had number average molecular weights >100,000 g/mol. DSC analysis revealed a first-order phase transition at , 20 °C, reflecting the crystalline nature of the linear alkyl side chains. Polymeric micelles were prepared by the solvent displacement method in water. Dynamic light scattering measurements support formation of a mixture of 20-nm-diameter unimolecular micelles and 60-nm particles comprised of an estimated 25 polymer molecules. UV,vis characterization of micelles formed from acetone,water solutions containing azobenzene confirmed encapsulation of the hydrophobic dye, suggesting their potential as new amphiphilic PLAs as drug delivery vehicles. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5227,5236, 2007 [source] Synthesis and Comparative Study of Nano-TiO2 Over Degussa P-25 in Disinfection of WaterPHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 3 2010S. Swetha Nanostructured TiO2 crystals were synthesized by gel to crystalline conversion. The crystals obtained were anatase form of titania averaging in 30 nm particles with an intrinsic band gap of 3.1 eV. The photocatalytic behavior was evaluated for the bactericidal effect in water, contaminated with the indicator organism Escherichia coli. The 100% photoinactivation of E. coli was achieved within 60 min with suspended nano-TiO2. The catalytic activity of synthesized nanosample was observed to be 2.6 times more than that of commercial TiO2 sample referred to as Degussa P-25. The photoinactivation of E. coli was tested with irradiation source of different wavelengths to substantiate the influence of particle size and nano crystallinity on electronic band structure. The photoactivity of nano titania enhanced to 1.625 times when the source of irradiation shifted from 360 to 400 nm while Degussa P-25 showed no change. [source] Rapid Expansion from Supercritical to Aqueous Solution to Produce Submicron Suspensions of Water-Insoluble DrugsBIOTECHNOLOGY PROGRESS, Issue 3 2000Timothy J. Young Stable suspensions of submicron particles of cyclosporine, a water-insoluble drug, have been produced by rapid expansion from supercritical to aqueous solution (RESAS). To minimize growth of the cyclosporine particles, which would otherwise occur in the free jet expansion, the solution was sprayed into an aqueous Tween-80 (Polysorbate-80) solution. Steric stabilization by the surfactant impedes particle growth and agglomeration. The particles were an order of magnitude smaller than those produced by RESS into air without the surfactant solution. Concentrations as high as 38 mg/mL for 400,700 nm particles were achieved in a 5.0% (w/w) Tween-80 solution. [source] | |||||||||||||