Search results for "X-Ray"
showing 10 items of 4234 documents
Study by static SIMS, XPS and UPS of the adsorption of cyanogen on (100) Ni surfaces
2000
Abstract The interaction of cyanogen with (100) Ni surfaces at room temperature was studied using secondary ion mass spectrometry in a static mode, and photoemission spectroscopies (XPS and UPS). It has been shown that cyanogen is adsorbed on this nickel surface in a dissociative mode: atomic carbon and nitrogen are present on the surface as well as CN fragments. These adsorbed species have been characterized by XPS and UPS. Increasing the temperature in the 400 K range increases the rate of the dissociation reaction of CN into atomic carbon and nitrogen. Moreover carbon is found to dissolved into the bulk for temperatures as low as 475 K. No evidence has been found of a polymerized form of…
A surface EXAFS study of thin nickel deposits on (110) TiO2 surfaces
1997
Abstract The first stages of nickel deposition on a clean (110) TiO 2 surface were studied using surface extended X-ray absorption fine structure (EXAFS). Experiments were performed on two kinds of nickel deposits, one of 0.8 equivalent monolayers and another of 1.6 equivalent monolayers. Depositions were performed on well characterized TiO 2 (110)-p(1 × 1) surfaces. The correlation of Auger experiments with EXAFS results showed that no islands were present on the surface; only two-dimensional growth of nickel was observed. Moreover, it was shown, in the case of the thinner deposit, that a model with nickel atoms forming chains in the channels determined by oxygen atoms on the surface is co…
Determination of the Absolute Density of Fe3+ and Ni2+ Ions in Langmuir-Blodgett Films
1996
By means of the Langmuir–Blodgett (LB) technique, mono- and multilayers of Ni2+ and Fe3+ containing fatty acid salts are transferred onto silicon wafers. After thermal treatment, oxidic layers can be produced. The absolute amounts of Fe3+ and Ni2+ ions per monolayer of LB film were measured and calculated by three different methods. In the case of nickel, the amount expected from theory and preparation conditions was obtained experimentally. In contrast, about twice the number of Fe3+ ions as expected is transferred. An explanation can be given by the presence of hydroxide groups bound to iron. The mean film thickness of the oxidic layers after thermal treatment was estimated where the thic…
Halogen bonding and host–guest chemistry between N-alkylammonium resorcinarene halides, diiodoperfluorobutane and neutral guests
2019
Single crystal X-ray structures of halogen-bonded assemblies formed between host N-hexylammonium resorcinarene bromide (1) or N-cyclohexylammonium resorcinarene chloride (2), and 1,4-diiodooctafluorobutane and accompanying small solvent guests (methanol, acetonitrile and water) are presented. The guests’ inclusion affects the geometry of the cavity of the receptors 1 and 2, while the divalent halogen bond donor 1,4-diiodooctafluorobutane determines the overall nature of the halogen bond assembly. The crystal lattice of 1 contains two structurally different dimeric assemblies A and B, formally resulting in the mixture of a capsular dimer and a dimeric pseudo-capsule. 1H and 19F NMR analyses …
Precatalyst or dosing-device? The [Pd2{μ-(C6H4) PPh2}2{μ-O2C(C6H5)}2] complex anchored on a carboxypolystyrene polymer as an effective supplier of pa…
2020
Abstract A new catalyst has been synthesized from the precursor [Pd2{μ-(C6H4) PPh2}2 {μ-O2C(C6H5)}2] immobilized on a carboxypolystyrene polymer that exhibits an excellent dispersion of the Pd (II) centers, reusability, and catalytic activity in front of phenyl bromides. The activity of this new material was studied in detail for the Suzuki-Miyaura reaction and compared to that of Pd nanoparticles (NPs) supported on UVM-7 (a mesoporous silica), and Pd NPs stabilized with polyvinylpirrolydone. The homogeneous/heterogeneous character of the catalytic process was determined from the results of the hot-filtration, centrifugation, poisoning, three phases tests, and from differential sensitivity …
ORR Activity and Stability of Co-N/C Catalysts Based on Silicon Carbide Derived Carbon and the Impact of Loading in Acidic Media
2018
This work was supported by the EU through the European Regional Development Fund under projects TK141 “Advanced materials and high-technology devices for energy recuperation systems” (2014-2020.4.01.15-0011), NAMUR ”Nanomaterials - research and applications” (3.2.0304.12-0397) and by the Estonian institutional research grant No. IUT20-13.
Structural Characterization of Surfactant-Coated Bimetallic Cobalt/Nickel Nanoclusters by XPS, EXAFS, WAXS, and SAXS
2011
Cobalt nickel bimetallic nanoparticles were synthesized by changing the sequence of the chemical reduction of Co(II) and Ni(II) ions confined in the core of bis(2-ethylhexyl)phosphate (2)., and Ni(DEHP)(2). The reduction was carried out by mixing, sequentially or contemporaneously, fixed amounts of n-heptane solution of Co(DEHP)2 and Ni(DEHP)2 micelles with a solution of sodium borohydride in ethanol at a fixed (reductant)/(total metal) molar ratio. This procedure involves the rapid formation of surfactant-coated nanoparticles, indicated as Co/Ni (Co after Ni), Ni/Co (Ni after Co), and Co + Ni (simultaneous), followed by their slow separation as nanostructures embedded in a sodium bis(2-eth…
Study of the role of sulfur functionalities in humic acids for uranium(VI) complexation
2009
Humic substances influence the speciation and migration behavior of toxic and radiotoxic metal ions, such as actinides, in the environment. Depending on their origin, humic substances contain different amounts of sulfur ranging from 0.1 to 3.6% and 0.5 to 1.43% in soil and aquatic humic substances, respectively [1]. Reduced, intermediately oxidized and highly oxidized sulfur functionalities occur in humic substances [1]. Although sulfur functionalities occur in small concentrations, they can play an important role in the complexation of selected metal ions. Knowledge about the impact of sulfur functionalities on the metal ion complexation by humic substances and their significance compared …
Total oxidation of naphthalene using bulk manganese oxide catalysts
2013
Several Mn2O3 catalysts have been synthesized using different preparation methods and tested for the total oxidation of naphthalene, a model polycyclic aromatic compound. The catalysts have been characterized by several physico-chemical techniques such as XRD, TPR, XPS, EDX and TEM. The surface area of the catalyst seems to be of paramount importance, since the mass normalized activity of catalysts increases as the surface area of the Mn2O3 catalysts increases. Consequently, a high surface area ordered mesoporous Mn2O3 catalyst, obtained through a nanocasting route using mesoporous KIT-6 silica as a hard template, was the most efficient catalyst for the deep oxidation of naphthalene. In add…
Long-Term Stability of TiS2–Alkylamine Hybrid Materials
2022
Layered TiS2 intercalated with linear alkylamines has recently attracted significant interest as a model compound for flexible n-type thermoelectric applications, showing remarkably high power factors at room temperature. The thermal and, particularly, environmental stability of such materials is, however, a still an open challenge. In this paper, we show that amine-intercalated TiS2 prepared by a simple mechanochemical process is prone to chemical decomposition through sulfur exsolution, and that the presence of molecular oxygen is likely to mediate the decomposition reaction. Through computational analysis of the possible reaction pathways, we propose that Ti-N adducts are formed as a con…