Search results for "stoichiometry"
showing 10 items of 270 documents
Effect of the Mo atom flow on the molybdenum growth on TiO2 (110) surface
2004
Abstract Molybdenum has been deposited at room temperature on stoichiometric TiO 2 (1 1 0) surfaces with two deposition rates: 0.1 equivalent monolayer (eqML) and 1.5 eqML min −1 . X-ray photoelectron spectroscopy and high-resolution transmission electron microscopy studies clearly reveal an effect of the deposition rate upon the growth mode and the interfacial reaction. Indeed, whereas a strong interfacial reaction between Mo and TiO 2 involves a Stranski–Krastanov growth mode with the formation of amorphous molybdenum oxide monolayers for the lowest deposition rate, no reaction can be observed for the highest deposition rate. Moreover in this latter case, the growth mode seems to be a 3D …
Defektanalyse von a-C- und CNx-Schichten mittels Röntgen-Photoemissions-Elektronenmikroskopie (X-PEEM)Characterization of stoichiometric defects in d…
2001
Amorphe Kohlenstoff- und Kohlenstoffnitridschichten werden vielseitig als Schutzschichten in der Industrie verwandt. Insbesondere werden in der Magnetfestplattenspeicherindustrie verschleisfeste sauerstoffundurchlassige Schutzschichten von wenigen Nanometern Dicke benotigt. Rontgen-Photoemissions-Elektronenmikroskopie (X-PEEM) stellt eine Analysetechnik zur Charakterisierung u.a. von Kohlenstoffschutzschichten dar, da sich Informationen uber die lokale Bindungsumgebung aus der Rontgenabsorptions-Nahkantenstruktur (XANES) gewinnen lassen. CVD-DLC- sowie a-C- und CNx-Schichten wurden analysiert. Fur die a-C-Schichten auf Si (100) wurde der Anteil sp2-hybridisierter Atome bestimmt und mit den …
Influence of Silver Deposits on the Photocatalytic Activity of Titania
1997
The objectives of depositing metals over semiconductor photocatalysts are to improve the electron-hole pair separation and to increase the rate of the reduction process due to the catalytic properties of the metal itself. Most of the deposited (noble) metals that have been studied belonged to group VIII. Very few studies concerned silver deposits. In the present work, the influence of deposited silver over anatase or rutile has been followed in three different types of reactions: (i) metal deposition, (ii) oxidation, and (iii) dehydrogenation. The final solids obtained in the last reaction (Pt/Ag/TiO{sub 2}) were also used as catalysts in two other test reactions to make comparison with TiO…
Symmetry and models of single-walled TiO2 nanotubes with rectangular morphology
2011
Abstract The formalism of line symmetry groups for one-periodic (1D) nanostructures with rotohelical symmetry has been applied for symmetry analysis of single-walled titania nanotubes (SW TiO2 NTs) formed by rolling up the stoichiometric two-periodic (2D) slabs of anatase structure. Either six- or twelve-layer (101) slabs have been cut from TiO2 crystal in a stable anatase phase. After structural optimization, the latter keeps the centered rectangular symmetry of initial slab slightly compressed along a direction coincided with large sides of elemental rectangles. We have considered two sets of SW TiO2 NTs with optimized six- and twelve-layer structures, which possess chiralities (−n, n) an…
Characterization and determination of poly(vinylpyrrolidone) by complexation with an anionic azo-dye and nonequilibrium capillary electrophoresis
2009
Using capillary zone electrophoresis in nonequilibrium conditions, the complexes of poly(vinylpyrrolidone) (PVP) with anionic azo-dyes dissociate following a first-order kinetics. Two peaks due to the remaining PVP-dye complexes and the equilibrium concentration of the free dye, plus an exponential region due to the dye liberated by the complexes during the electrophoretic run, are obtained. This behaviour was closely similar to that described in the literature for protein-probe and DNA-protein mixtures, upon application of the technique known as nonequilibrium capillary electrophoresis of equilibrium mixtures or NECEEM. Using Congo Red and Acid Blue 113, information about the maximal stoic…
Dinuclear and tetranuclear complexes of copper coordinated by an anthracene-based new μ-bis(tridentate) ligand: Synthesis, structure, spectroscopy an…
2016
Abstract Copper(II) complexes of an anthracene-based new μ-bis(tridentate) ligand, N,N′-bis[anthracene-2-ylmethyl]-N,N′-bis[carboxymethyl]-1,3-diaminopropan-2-ol (H3acdp) with mixed donating groups, have been studied in solid state as well as in solution. The reaction of stoichiometric amounts of CuSO4·5H2O and the ligand H3acdp in the presence of NaOH at ambient temperature in methanol-dichloromethane, afforded a new dinuclear copper complex, [Cu2(acdp)(MeO)(MeOH)2] (1). On the other hand, the reaction of stoichiometric amounts of Cu(OAc)2·H2O and the ligand H3acdp in the presence of NaOH at ambient temperature in methanol-dichloromethane yielded, a novel tetranuclear copper complex, [Cu4(…
Solubility and stability of liebigite, Ca2UO2(CO3)3·10H2O(cr), in dilute to concentrated NaCl and NaClO4 solutions at T = 22–80 °C
2019
Abstract The solubility and thermodynamic stability of a synthetic liebigite was investigated in NaCl and NaClO4 solutions within a wide range of ionic strength (0.03 m ≤ Im ≤ 5.61 m), pH (7 ≤ pHm ≤ 9, with pHm = –log [H+]) and temperature (22 °C ≤ T ≤ 80 °C) conditions. A comprehensive characterization of the synthetic solid phase using XRD, quantitative chemical analysis, TG–DTA, SEM–EDS, IR and Raman spectroscopy confirmed the stoichiometry of Ca2UO2(CO3)3·10H2O(cr). At room temperature, liebigite remains stable and controls the solubility of U(VI) in the investigated NaCl and NaClO4 systems with Im ≤ 0.51 m. For the same temperature but high ionic strength (5.61 m NaCl), liebigite trans…
Application of the Generalized Molar-Ratio Method to the Determination of the Stoichiometry and Apparent Binding Constant of Nanoparticle-Organic Cap…
2015
A generalization of the molar-ratio method is applied to the determination of the stoichiometry and apparent binding constant of metal nanoparticle-organic capping complexes (MmLx) using voltammetric data for the oxygen reduction reaction (ORR) in air-saturated aqueous phosphate buffer solutions. The method is applied to the formation of binary nanohybrids consisting of gold nanoparticles (AuNPs) capped with a rigid spacer, cucurbit[7]uril (CB), termed AuNP@CB, as well as to the formation of their ternary complexes (MmLxBz) with methylene blue (MB), termed AuNP@CB@MB. The obtained stoichiometries correspond to binding of four Au surface atoms for each CB unit.
Complexes of Tungsten(VI) with Mucic Acid: a Spectrophotometric and Polarimetric Study in Aqueous Solution
1986
Abstract Spectrophotometric work on mucic acid-W(VI) system shows the formation of three different oxoanion complexes in aqueous solution; their stability is dependent upon pH. One of the complexes is monomeric tungstodimucate and the other two are 2/2 species. An anomalous cryoscopic behaviour, similar to that of W(VI) tartaric system, has been observed for the dimeric complex formed at higher pH. The stoichiometries and conditional dissociation constants have been polarimetrically determined by means of competitive reactions between the mucic and tartaric ligands. 1 H and 13 C NMR spectra have been interpreted for the similar complex species of both mucic and tartaric acids.
Induced-Fit Molecular Recognition with Water-Soluble Cavitands
2000
Synthesis of novel water-soluble cavitands 1 and 2 and their complexes—the caviplexes—is described. The solubility in water derives from four primary ammonium groups on the lower rim and eight secondary amide groups on the upper rim. Cavitands 1 and 2 exist as D2d velcraplex dimers in aqueous solution but the addition of lipophilic guests 15–24 induces conformational changes to the vase-like structures. The internal cavity dimensions are 8×10 A, and the exchange rates of guests in the caviplexes are slow on the NMR timescale (room temperature and 600 MHz). The direct observation of bound species and the stoichiometry of the complexes is reported. The association constants (Ka) between 0.4×1…