Search results for "Chemisorption"

Formation and Characterization of Self-Assembled Films of Thiol-Derivatized Poly(Dimethylsiloxane) on Gold

1997

Poly(dimethylsiloxane) (PDMS) copolymers containing propanethiol side chain “stickers” for forming self-assembled films on gold surfaces have been studied by various experimental techniques including ellipsometry, contact angle measurements, FT-IR, angle-dependent XPS, and ToF−SIMS. The results show that the thiol-containing side chains do not all chemisorb to the gold surfaces. In addition, the concentration of these sticker units was found to have a dominant effect on the polymer film thickness, the surface wetting properties, and the orientation of the PDMS backbone. Ab initio calculations reveal that the IR-active PDMS Si−O stretching bands can be used as indications of chain orientatio…

Cluster calculations for H2dissociation on Cu and Ni

1988

Self-consistent cluster calculations have been carried out for hydrogen dissociation on Cu and Ni clusters using local-density theory and the LCAO-DVM expansion. We find physisorption, chemisorption and dissociation minima in the resulting two-dimensional potential energy surfaces, and for the Ni cluster, also an indication of the associative molecular chemisorption state. For Cu we find a considerable barrier at the seam separating the molecular chemisorption and dissociative minima. The analysis of one-electron levels supports the picture of Harris and Andersson that the s to d conversion present on Ni surfaces does not similarly lower the barrier on Cu surface.

Surface properties of AlInGaN/GaN heterostructure

2016

Abstract Surface structural, electronic and electrical properties of the quaternary alloy AlInGaN/GaN heterostructures are investigated. Surface termination, atomic arrangement, electronic and electrical properties of the (0001) surface and (10–11) V-defect facets have been experimentally analyzed using various surface sensitive techniques including spectroscopy and microscopy. Moreover, the effect of sub-band gap (of the barrier layer) illumination on contact potential difference (VCPD) and the role of oxygen chemisorption have been studied.

Ten Facets, One Force Field: The GAL19 Force Field for Water - Noble Metal Interfaces

2020

<div>Understanding the structure of the water/metal interfaces plays an important role in many are as ranging from surface chemistry to environmental processes. Due to their intrinsic complexity, the water/metal interfaces cannot yet be adequately described by quantum mechanical approaches and accurate force-fields are therefore needed. We develop and parametrize GAL19, a novel force-field to describe the interaction of water with two facets (111 and 100) of five metals (Pt, Pd, Au, Ag, Cu). To increase transferability compared to its predecessor GAL17, the water-metal interaction is described as a sum of pair-wise terms. The interaction energy has three contributions: (i) physisorption …

Reversible Chemisorption of Sulfur Dioxide in a Spin Crossover Porous Coordination Polymer

2013

The chemisorption of sulfur dioxide (SO2) on the Hofmann-like spin crossover porous coordination polymer (SCO-PCP) {Fe(pz)[Pt(CN)4]} has been investigated at room temperature. Thermal analysis and adsorption-desorption isotherms showed that ca. 1 mol of SO2 per mol of {Fe(pz)[Pt(CN)4]} was retained in the pores. Nevertheless, the SO2 was loosely attached to the walls of the host network and completely released in 24 h at 298 K. Single crystals of {Fe(pz)[Pt(CN)4]}·nSO2 (n ≈ 0.25) were grown in water solutions saturated with SO2, and its crystal structure was analyzed at 120 K. The SO2 molecule is coordinated to the Pt(II) ion through the sulfur atom ion, Pt-S = 2.585(4) Å. This coordination…

Tuning the magneto-structural properties of non-porous coordination polymers by HCl chemisorption.

2011

Responsive materials for which physical or chemical properties can be tuned by applying an external stimulus are attracting considerable interest in view of their potential applications as chemical switches or molecular sensors. A potential source of such materials is metal-organic frameworks. These porous coordination polymers permit the physisorption of guest molecules that can provoke subtle changes in their porous structure, thus affecting their physical properties. Here we show that the chemisorption of gaseous HCl molecules by a non-porous one-dimensional coordination polymer instigates drastic modifications in the magnetic properties of the material. These changes result from profoun…

Iodine on a magnetized iron film evidence for a magnetic coupling

1993

Abstract Spin-resolved photoelectron spectra of iodine chemisorbed on a magnetized iron (110) surface have been taken using unpolarized VUV light. The partial spin spectra reveal the I 5p x and 5p z signals being split by up to 0.35 eV. This exchange splitting occurs due to hybridization of adsorbate and substrate bands as a consequence of the chemical bond of the halogen atoms to the iron surface.

Oxidative Addition of Halogens on Open Metal Sites in a Microporous Spin-Crossover Coordination Polymer

2009

Selective chemisorption of carbon monoxide by organic-inorganic hybrid materials incorporating cobalt(III) corroles as sensing components.

2007

Twenty-one hybrid materials incorporating cobalt(III) corrole complexes were synthesized by a sol–gel process or by grafting the metallocorrole onto a mesostructured silica of the SBA-15 type. All the materials show an almost infinite selectivity for carbon monoxide with respect to dinitrogen and dioxygen in the low-pressure domain where the chemisorption phenomenon is predominant. This peculiar property is of prime importance for an application as a CO sensor. The selectivity slightly decreases at high pressures where nonselective physisorption phenomena mainly occur. The percentage of active sites for CO chemisorption ranges from 22 to 64 %. This low percentage may be attributable to inte…

Activity of SiO2 supported gold-palladium catalysts in CO oxidation

2003

Abstract Bimetallic Au-Pd catalysts supported on silica with different Au/Pd atomic ratios were prepared by simultaneous reduction of palladium and gold precursors by ethanol in the presence of the polymer, polyvinylpyrrolidone (PVP). Formation of alloyed particles was detected by means of X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM) and CO chemisorption measurements. The catalysts were tested in the catalytic oxidation of CO using a plug–flow reactor. The CO conversion was determined as a function of temperature. The monometallic palladium and the palladium-rich catalysts behaved quite similarly and were the most active catalysts. …