Search results for "Surfaces"

A Novel Zeolite-Induced Population of a Planar Viologen Conformation. New Viologen Charge Transfer Complexes and Alkene/Viologen/Zeolite Arrays

2004

A rare example of a novel zeolite-induced conformational change and a mechanism for this process are suggested in order to rationalize an unexpected spontaneous intrazeolite reduction observed during preparation of a new viologen (MQ2+)-doped zeolite (NaY). In addition, the formations of six new alkene/viologen/ zeolite charge transfer (CT) arrays using NaMQY and the previously reported NaMVY are also reported. The binding constants between MQ2+ and MV2+ and 2,3-dimethyl-2-butene (TME) were determined using the Benesi-Hildebrand approach, and the stabilities of these CT complexes are compared to their intrazeolite analogue.

Stratification in Drying Polymer–Polymer and Colloid–Polymer Mixtures

2017

Drying polymer-polymer and colloid-polymer mixtures were studied using Langevin dynamics computer simulations. Polymer-polymer mixtures vertically stratified into layers, with the shorter polymers enriched near the drying interface and the longer polymers pushed down toward the substrate. Colloid-polymer mixtures stratified into a polymer-on-top structure when the polymer radius of gyration was comparable to or smaller than the colloid diameter, and a colloid-on-top structure otherwise. We also developed a theoretical model for the drying mixtures based on dynamical density functional theory, which gave excellent quantitative agreement with the simulations for the polymer-polymer mixtures a…

Structural Investigation of Water/Lecithin/Cyclohexane Microemulsions by FT-IR Spectroscopy

1995

Abstract FT-IR spectra of water/lecithin/deuterated cyclohexane microemulsions as a function of water/lecithin molar ratio R ( R = [water]/[lecithin]) at various volume fractions ( O ) of the micellar phase have been recorded at 25°C. After elimination of the small spectral contributions due to deuterated cyclohexane and normalization, the shape of the C–H stretching band due to lecithin has been found dependent upon R and O whereas that of the O–H stretching band has been found dependent only upon R . The change in shape of the C–H band was interpreted in terms of a modification of the lecithin alkyl chain packing order. The analysis of the O–H band provides evidence that the hydroxylic gr…

Photooxidation and Stabilization of Photooxidized Polyethylene and of its Monopolymer Blends

2003

The increasing use of products from recycled polymers, or from blends with recycled polymers exposed to the outdoors, implies the need for good weathering resistance. This is particularly important when the recycled material comes, in turn, from products exposed during their lifetime to the sun. In this case the presence of C=O groups in the macromolecular chains strongly increases the photooxidative degradation kinetics of these secondary materials. In this work the change of the photooxidative degradation of blends of virgin and photooxidized polyethylene was evaluated as a function of the C=O content present in the material. As expected, the presence of the C=O groups strongly increases …

Structural characterization of U(VI) surface complexes on kaolinite in the presence of humic acid using EXAFS spectroscopy.

2007

To determine the influence of humic acid (HA), pH, and presence of atmospheric CO2 on the sorption of U(VI) onto kaolinite, the structure of the surface complexes was studied by U L III-edge extended X-ray absorption fine structure (EXAFS) spectroscopy. The best fits to the experimental EXAFS data were obtained by including two uranium coordination shells with two axial (O ax) and five equatorial (O eq) oxygen atoms at 1.77+/-0.02 and 2.34+/-0.02 A, respectively, and two coordination shells with one Al/Si atom each at 3.1 and 3.3 A. As in the case of the binary system U(VI)-kaolinite, uranium forms inner-sphere surface complexes by edge sharing with aluminum octahedra and/or silicon tetrahe…

Cationic Au Nanoparticle Binding with Plasma Membrane-like Lipid Bilayers: Potential Mechanism for Spontaneous Permeation to Cells Revealed by Atomis…

2014

Despite being chemically inert as a bulk material, nanoscale gold can pose harmful side effects to living organisms. In particular, cationic Au nanoparticles (AuNP+) of 2 nm diameter or less permeate readily through plasma membranes and induce cell death. We report atomistic simulations of cationic Au nanoparticles interacting with realistic membranes and explicit solvent using a model system that comprises two cellular compartments, extracellular and cytosolic, divided by two asymmetric lipid bilayers. The membrane-AuNP+ binding and membrane reorganization processes are discovered to be governed by cooperative effects where AuNP+, counterions, water, and the two membrane leaflets all contr…

Divide and Protect: Passivating Cu(111) by Cu-(benzotriazole)2

2012

Binding of benzotriazolate anion (BTA) to copper complexes and Cu(111) surface was investigated by density functional theory calculations. [BTACuBTA]1– was found to be a very stable complex that BT...

DFT Study on the Complex Reaction Networks in the Conversion of Ethylene to Ethylidyne on Flat and Stepped Pd

2009

Adsorption and conversion of ethylene to ethylidyne on flat (111) and stepped Pd surfaces have been studied with the aim to unravel the complex chemistry of small organic molecules on Pd. These pro...

Amorphous polyphosphate nanoparticles: application of the morphogenetically active inorganic polymer for personalized tissue regeneration

2019

Preparation and Characterization of Tungsten Chalcogenide Photocatalysts

1997

Tungsten chalcogenides powders have been prepared by sulfidation of WO3 with gaseous H2S. Different mixed WS2/WO3 systems have been obtained by varying the amount of initial WO3 powder, the time, o...