Search results for "borohydride"
showing 10 items of 34 documents
Combined small-angle x-ray scattering/extended x-ray absorption fine structure study of coated Co nanoclusters in bis(2-ethylhexyl)sulfosuccinate
2009
Chemically stable cobalt nanostructures have been prepared with Co(II) reduction in the confined space of cobalt bis(2-ethylhexyl)sulfosuccinate, Co(AOT)2, reverse micelles dispersed in n-heptane. The reaction was carried out by adding a solution of sodium borohydride in ethanol (1% weight) to a 0.2M micellar solution of Co(AOT)2 in n-heptane at a reductant to Co(II) molar ratio of 4. This procedure involves the rapid formation of surfactant-coated Co nanoparticles followed by their slow separation as nanostructures embedded in a sodium bis(2-ethylhexyl)sulfosuccinate matrix. The resulting composites, characterized by extended x-ray absorption fine structure and small-angle x-ray scattering…
Gold Nanoparticles on 3D-Printed Filters : From Waste to Catalysts
2019
Three-dimensionally printed solid but highly porous polyamide-12 (PA12) plate-like filters were used as selective adsorbents for capturing tetrachloroaurate from acidic solutions and leachates to prepare PA12–Au composite catalysts. The polyamide-adsorbed tetrachloroaurate can be readily reduced to gold nanoparticles by using sodium borohydride, ascorbic acid, hydrogen peroxide, UV light, or by heating. All reduction methods led to polyamide-anchored nanoparticles with an even size distribution and high dispersion. The particle sizes were somewhat dependent on the reduction method, but the average diameters were typically about 20 nm. Particle sizes were determined by using a combination of…
Nanoconfined mixed Li and Mg borohydrides as materials for solid state hydrogen storage
2012
Abstract Several mixtures of LiBH4 and Mg(BH4)2 borohydrides in different stoichiometric ratios (1:0, 2:1, 1:1, 1:2, 0:1), prepared by high energy ball milling, have been investigated with X-ray powder diffraction and thermal programmed desorption (TPD) volumetric analysis to test the dehydrogenation kinetics in correlation with the physical mixture composition. Afterwards mixed and unmixed borohydrides were dispersed on high specific surface area ball milled graphite by means of the solvent infiltration technique. BET and statistical thickness methods were used to characterize the support surface properties, and SEM micrographs gave a better understanding of the preparation techniques. It …
Silver nanoparticles stabilized by a polyaminocyclodextrin as catalysts for the reduction of nitroaromatic compounds
2015
Abstract Silver nanoparticles stabilized by means of poly -(6- N , N -dimethyl-propylenediamino)-(6-deoxy)-β-cyclodextrin were synthesized, characterized by different techniques (UV–vis spectroscopy, Dynamic Light Scattering, High Resolution Transmission Electron Microscopy, Fourier-transform IR Spectroscopy) and used as catalysts for the reduction of various nitrobenzene derivatives with sodium borohydride. The nanocomposites obtained appear to have an organized structure, with a metal core surrounded by a layer-structured coating shell. Kinetic data, rationalized in terms of a modified Langmuir–Hinshelwood model, evidenced a non-linear dependence of the reaction rate on the concentration …
Determination of ultratrace bismuth in milk samples by atomic fluorescence spectrometry.
2003
Abstract A sensitive procedure was developed for determination of bismuth (Bi) in milk samples by hydride generation atomic fluorescence spectrometry (HG–AFS) after microwave-assisted sample digestion with HNO3 and H2O2. The method provides a sensitivity of 1832 fluorescence units (ng/mL) with a detection limit of 0.01 ng/mL, which corresponds to 20 pg absolute limit of detection, equivalent to 0.50 ng/g in the original sample. Application of the methodology to cow milk samples from the Spanish market showed the presence of Bi at a concentration of 11.8–28.8 ng/g, which compared well with data obtained after dry ashing of samples and with data obtained by inductively coupled plasma–mass spe…
Fullerene-ionic-liquid conjugates: a new class of hybrid materials with unprecedented properties.
2015
A modular approach has been followed for the synthesis of a series of fullerene-ionic-liquid (IL) hybrids in which the number of IL moieties (two or twelve), anion, and cation have been varied. The combination of C60 and IL give rise to new unique properties in the conjugates such as solubility in water, which was higher than 800 mg mL(-1) in several cases. In addition, one of the C60 -IL hybrids has been employed for the immobilization of palladium nanoparticles through ion exchange followed by reduction with sodium borohydride. Surprisingly, during the reduction several carbon nanostructures were formed that comprised nano-onions and nanocages with few-layer graphene sidewalls, which have…
Straightforward preparation of highly loaded MWCNT-polyamine hybrids and their application in catalysis
2020
Multiwalled carbon nanotubes (MWCNTs) were easily and efficiently functionalised with highly cross-linked polyamines. The radical polymerisation of two bis-vinylimidazolium salts in the presence of pristine MWCNTs and azobisisobutyronitrile (AIBN) as a radical initiator led to the formation of materials with a high functionalisation degree. The subsequent treatment with sodium borohydride gave rise to the reduction of imidazolium moieties with the concomitant formation of secondary and tertiary amino groups. The obtained materials were characterised by thermogravimetric analysis (TGA), elemental analysis, solid state 13C-NMR, Fourier-transform infrared spectroscopy (FT-IR), transmission ele…
Chromatographic and mass spectrometric characteristics of 20-dihydroaldosterone.
1992
The 20 alpha-reduced derivative of aldosterone, 20 alpha-dihydroaldosterone, was needed as reference compound in order to continue the studies on 18-hydroxylation in the Y-1 adrenal cell line. It was obtained by reduction of aldosterone with sodium borohydride. Analysis of the products of the reaction as methoxime trimethylsilyl (MO-TMS) derivatives by gas chromatography (GC) and GC-mass spectrometry (GC-MS) showed three possible forms of the compound. Their identification was confirmed by comparison with the products obtained by stereospecific reduction of aldosterone using 3 alpha,20 beta-hydroxysteroid dehydrogenase. Chromatographic behavior and mass spectra are given for the three forms…
Free and bound hydroxyl and carboxyl groups in the cutin of Quercus suber leaves
1984
Abstract The number of free and bound hydroxyl and carboxyl groups of the cutin of Quercus suber leaves was investigated by the lithium borohydride hydrogenolysis of mesyl-cutin compared with the lithium borohydride hydrogenolysis of untreated cutin. Fifty per cent of the vic -diol groups of the trihydroxy C 18 acid component and twenty five per cent of the secondary hydroxyl groups of the dihydroxy C 16 acid component are free. The rest of the secondary and all of the primary hydroxyl groups are esterified; all carboxyl groups are esterified.
5-Substituted 4,5-Dihydro-1,2,4-triazin-3(2H)-ones from the Unprecedented Reaction between α-N-Protected Amino Acid Hydrazides and NaBH4
2006
α-N-Protected amino acid hydrazides (1) readily reacted with NaBH4 to afford 5-substituted 4,5-dihydro-1,2,4-triazin-3(2H)-one derivatives 2 in good yields. Unfortunately, the reaction caused partial racemization at the α-amino acidic carbon atom of the starting hydrazide. A mechanism, supported by experimental evidence, has been proposed in an attempt to explain this to date unprecedented reaction. The structure of compounds 2 was confirmed by X-ray structural analysis. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)