Search results for "GST"
showing 10 items of 874 documents
Synthesis, characterization, and hierarchical organization of tungsten oxide nanorods: spreading driven by Marangoni flow.
2009
Tungsten oxide nanorods were synthesized by a soft chemistry approach using tungsten alkoxide and trioctyl amine and oleic acid as the surfactants. The optical properties of the nanorods were studied. The nanorods were found to be soluble in a wide range of solvents like chloroform, cyclohexane, and so on. Upon solvent evaporation, the nanorods formed hierarchically organized solid state structures. Depending on the solvent used, the nanorods organized in different mesostructures. Moreover, the organization of the nanorods from mixtures of polar and nonpolar solvents was studied. Here, the Marangoni effect resulting from differences in the surface tensions of the two solvents was found to p…
Dalton communication. Crystal structure and oxo-transfer properties of [NH4]2[WVIO2{O2CC(S)Ph2}2]
1994
The complex [NH4]2[WVIO2{O2CC(S)Ph2}2] is the first example of a non-dithiolene tungsten complex capable of oxidising benzoin to benzil in methanol; the reduced complex product formed, presumably a monomeric WVIO species, was reoxidised with nitrate ions, regenerating the starting WVIO2 complex which then acts as a true homogeneous catalyst.
A New Heptanuclear Cobalt(II) Cluster Encapsulated in a Novel Heteropolyoxometalate Topology: Synthesis, Structure, and Magnetic Properties of [Co7(…
2004
The synthesis and the structural and magnetic characterization of a novel heptanuclear cobalt cluster encapsulated in a heteropolyoxotungstate is reported. This complex shows how it is possible to control the nuclearity of the Co clusters formed in a tungstate solution by slightly changing the synthetic conditions, and the relevance of pH in this regard. This heptanuclear complex [Co7(H2O)2(OH)2P2W25O94]16- (Co7) crystallizes in the triclinic space group P1 (a = 12.3403(6) A, b = 22.5966(11) A, c = 23.2645(12) A, α = 68.7830(11)°, β = 83.7981(12)°, γ = 78.5423(13)°, V = 5922.4(5) A3, Z = 2) and is formed by six CoO6 octahedra from two Co3 trimers sustained by Keggin trivacant fragments held…
Modes of complexation of non-substituted and substituted tetraazamacrocycles with Group 6 metal carbonyls. X-ray structure of [(permethylcyclam)Mo(CO…
1995
Abstract Reactions of complexation of tetraazamacrocycles L with Group 6 metal carbonyls [M(CO)6](M = Cr, Mo, or W) lead to [LM(CO)4], [LM(CO)3] or [LM(CO)2] entities, depending both on the size of the macrocycle and on the metal M. The structure of one representative complex [(permethylcyclam)Mo(CO)4] has been determined by X-ray diffraction (permethylcyclam: 1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane).
Aminobis(phenolate)s of imidomolybdenum(VI) and -tungsten(VI)
2009
Abstract The reactions of trans-[MoO(ONOMe)Cl2] 1 (ONOMe = methylamino-N,N-bis(2-methylene-4,6-dimethylphenolate) dianion) and trans-[MoO(ONOtBu)Cl2] 2 (ONOtBu = methylamino-N,N-bis(2-methylene-4-methyl-6-tert-butylphenolate) dianion) with PhNCO afforded new imido molybdenum complexes trans-[Mo(NPh)(ONOMe)Cl2] 3 and trans-[Mo(NPh)(ONOtBu)Cl2] 4, respectively. As analogous oxotungsten starting materials did not show similar reactivity, corresponding imido tungsten complexes were prepared by the reaction between [W(NPh)Cl4] with aminobis(phenol)s. These reactions yielded cis- and trans-isomers of dichloro complexes [W(NPh)(ONOMe)Cl2] 5 and [W(NPh)(ONOtBu)Cl2] 6, respectively. The molecular st…
Cluster-model density functional study of a W–Cu(100) STM junction
1999
Abstract In this article, we investigate the electronic properties of different clusters modelling a tungsten tip, the Cu(1 0 0) surface and interacting W–Cu(1 0 0) systems in STM configuration. Electronic structure calculations are carried out within the LDA approximation of the Density Functional Theory (DFT). Both integrated (densities of states) and local properties (electronic density and electrostatic potential) are considered. The study is performed for top and hollow surface sites and two different tip–sample separations.
Between Solid America and Fragile Chinatown in Maxine Hong Kingston’s The Woman Warrior
2021
The article traces mixed affiliations of the narrator of Maxine Hong Kingston’s The Woman Warrior (1976), permanently split between the world of Chinatown and broader American society outside Chinatown, both places crucial for the narrator in the on-going process of subjectivity construction. While both of these worlds constantly interpellate her, each of them entails a fair measure of hindrance and empowerment. The article undermines the criticism leveled at Kingston’s The Woman Warrior by a section of the Chinese American community represented primarily by Frank Chin. Chin accused Kingston of pandering to white tastes and white readers’ expectations of Chinese American authors. That, acco…
Fuel Cell Performances of Bio-Membranes Made of Chitosan-Polyelectrolyte Thin Films and Nanowires into Anodic Alumina Membranes
2012
Chitosan (CS) / Phosphotungstic acid (PTA) polyelectrolytes in the shape of thin films and nanowires supported by Anodic Alumina Membranes (AAM) have been fabricated through solution cast and filtration techniques, respectively. Their ability to function in a H2/O2 fuel cell under mild conditions (room temperature, low humidity and low Pt loading) is proved for the first time. The fabricated membrane electrode assemblies produce power peaks of ~20 mW cm-2 for both films and nanowires. The CS/PTA films (20-40 μm thick) are able to produce a quite constant power density of ~10 mW cm-2 recorded for at least 7 h. The gradual decrease of the power output with time observed for CS/PTA nanowires i…
Influence of synthesis conditions on the performance of chitosan–Heteropolyacid complexes as membranes for low temperature H2–O2 fuel cell
2015
Flat, free-standing chitosan/phosphotungstic acid (PTA) polyelectrolyte membranes were prepared by in-situ ionotropic gelation process at room temperature on porous alumina support firstly impregnated by H3PW12O40. Scanning electron microscopy revealed the formation of compact and homogeneous membranes, whose thickness resulted to be dependent on chitosan concentration and reticulation time. X-ray diffraction and Fourier transform infrared spectroscopy (FTIR) evidenced the formation of almost amorphous membrane without appreciable concentration of not protonated NH2 groups and PTA3- ions with preserved Keggin structure. Membranes were tested as proton conductor in low temperature H2-O2 fuel…
Chitosan-phosphotungstic acid complex as membranes for low temperature H2-O2 fuel cell
2015
Abstract Free-standing Chitosan/phosphotungstic acid polyelectrolyte membranes were prepared by an easy and fast in-situ ionotropic gelation process performed at room temperature. Scanning electron microscopy was employed to study their morphological features and their thickness as a function of the chitosan concentration. The membrane was tested as proton conductor in low temperature H 2 –O 2 fuel cell allowing to get peak power densities up to 350 mW cm −2 . Electrochemical impedance measurements allowed to estimate a polyelectrolyte conductivity of 18 mS cm −1 .