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Structure of Nd10W22O81 from high-resolution electron microscopy and X-ray powder diffraction (2001)

Grenthe, Carl ; Guagliardi, Antonietta ; Sundberg, Margareta ; [et al.]

Copenhagen : International Union of Crystallography (IUCr)

Acta crystallographica 57 (2001), S. 13-19

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ISSN: 1600-5740

Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001

Topics: Chemistry and Pharmacology , Geosciences , Physics

Notes: The crystal structure of Nd10W22O81, neodymium tungstate, has been determined using a combination of high-resolution transmission electron microscopy and X-ray powder diffraction methods. The unit-cell dimensions determined from X-ray data are a = 3.8613 (1), b = 35.9431 (1), c = 21.8900 (1) Å, V = 3038.05 Å3, Z = 2, space group Pbcm. The structure is built up of pentagonal columns (PCs) connected to ReO3-type fragments consisting of three octahedra, thus forming W9O32 units. These units form `pillars' along a. These `pillars' are joined by pairs of tilted octahedra (W2O11 groups) to form corrugated layers perpendicular to b. The Nd atoms are located in the space between these layers and form the only link between them. Interstitial O atoms are located between two of the Nd atoms. The formula Nd10W22O81 can thus be alternatively given as Nd5W11O39 + x (x ∼ 1.5), where x represents the interstitial O atoms. Nd10W22O81 is a new type of PC structure.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1107/S0108768100013203

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Catalytic properties of layered gold-palladium colloidsDedicated to Professor Max Herberhold on the occasion of his 60th birthday (1996)

Schmid, GÜNter ; West, Heike ; Malm, Jan-Olle ; [et al.]

Weinheim : Wiley-Blackwell

Chemistry - A European Journal 2 (1996), S. 1099-1103

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ISSN: 0947-6539

Keywords: catalysis ; colloids ; gold-palladium colloids ; HRTEM ; hydrogenations ; Chemistry ; General Chemistry

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Notes: Layered bimetallic gold-palladium colloids in the size range of 20-56 nm have been synthesized by the seed=growth method: gold seeds were convered by palladium layers of various thickness and vice vaers. The outer metal was coordinated by trisulfonated triphenylphosphine and sodium sulfanilate ligands to stabilize the bimetallic particles to such an extent that they could be isolated in the solid state. Owing to the hydrophilic ligand shell, redispersion in water was posible in any concentration. High-resolution transmission electronn microscopy and energy-dispersive X-ray analysis was used to characterized the colloids. Stabilized and nonstabilized gold-palladium and palladium-gold systems on a TiO2 support were used as heterogeneous catalysts for the hydrogenation of hex-2-yne to cis-hex-2-ene. Both the palladium-plated gold seeds and the gold-plated palladium particles showed considerably increased activities compared with the pure metals. The ligand shell seems not to influence the catalytic behavior because protected and unprotected colloids behave very similarly.

Additional Material: 6 Ill.