Water Adsorption Microcalorimetry Model: Deciphering Surface Energies and Water Chemical Potentials of Nanocrystalline Oxides

2014 ◽  
Vol 118 (19) ◽  
pp. 10131-10142 ◽  
Author(s):  
John W. Drazin ◽  
Ricardo H. R. Castro
Keyword(s):  
Water Adsorption ◽  
Adsorption Microcalorimetry ◽  
Surface Energies ◽  
Chemical Potentials ◽  
Nanocrystalline Oxides

scholarly journals A comparative study of surface energies and water adsorption on Ce-bastnäsite, La-bastnäsite, and calcite via density functional theory and water adsorption calorimetry

2017 ◽  
Vol 19 (11) ◽  
pp. 7820-7832 ◽  
Author(s):  
Sriram Goverapet Srinivasan ◽  
Radha Shivaramaiah ◽  
Paul R. C. Kent ◽  
Andrew G. Stack ◽  
Richard Riman ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Comparative Study ◽  
Density Functional ◽  
Rational Design ◽  
Water Adsorption ◽  
Structural Features ◽  
Adsorption Calorimetry ◽  
Functional Theory ◽  
Surface Energies

Rational design of bastnäsite specific collector molecules must exploit its surface structural features.

Structure, Stability and Water Adsorption on Ultra-Thin TiO2 Supported on TiN

2019 ◽  
Author(s):  
Jose Julio Gutierrez Moreno ◽  
Marco Fronzi ◽  
Pierre Lovera ◽  
alan O'Riordan ◽  
Mike J Ford ◽  
...  
Keyword(s):  
Density Functional ◽  
Water Adsorption ◽  
Chemical Potential ◽  
Energy Gap ◽  
Molecular Water ◽  
Structure Stability ◽  
Ambient Conditions ◽  
Rutile Structure ◽  
The Stability ◽  
The One

<p></p><p>Interfacial metal-oxide systems with ultrathin oxide layers are of high interest for their use in catalysis. In this study, we present a density functional theory (DFT) investigation of the structure of ultrathin rutile layers (one and two TiO<sub>2</sub> layers) supported on TiN and the stability of water on these interfacial structures. The rutile layers are stabilized on the TiN surface through the formation of interfacial Ti–O bonds. Charge transfer from the TiN substrate leads to the formation of reduced Ti<sup>3+</sup> cations in TiO<sub>2.</sub> The structure of the one-layer oxide slab is strongly distorted at the interface, while the thicker TiO<sub>2</sub> layer preserves the rutile structure. The energy cost for the formation of a single O vacancy in the one-layer oxide slab is only 0.5 eV with respect to the ideal interface. For the two-layer oxide slab, the introduction of several vacancies in an already non-stoichiometric system becomes progressively more favourable, which indicates the stability of the highly non-stoichiometric interfaces. Isolated water molecules dissociate when adsorbed at the TiO<sub>2</sub> layers. At higher coverages the preference is for molecular water adsorption. Our ab initio thermodynamics calculations show the fully water covered stoichiometric models as the most stable structure at typical ambient conditions. Interfacial models with multiple vacancies are most stable at low (reducing) oxygen chemical potential values. A water monolayer adsorbs dissociatively on the highly distorted 2-layer TiO<sub>1.75</sub>-TiN interface, where the Ti<sup>3+</sup> states lying above the top of the valence band contribute to a significant reduction of the energy gap compared to the stoichiometric TiO<sub>2</sub>-TiN model. Our results provide a guide for the design of novel interfacial systems containing ultrathin TiO<sub>2</sub> with potential application as photocatalytic water splitting devices.</p><p></p>

Some Approximate Atomic and Molecular Energy Formulas

2003 ◽  
Vol 68 (1) ◽  
pp. 61-74 ◽  
Author(s):  
Peter Politzer ◽  
Abraham F. Jalbout ◽  
Ping Jin
Keyword(s):  
Density Functional ◽  
Electrostatic Potentials ◽  
Hartree Fock ◽  
Chemical Potentials ◽  
Approximate Formulas

We have tested several approximate formulas that relate atomic and molecular energies to the electrostatic potentials at the nuclei, V0 and V0,A, respectively. They are based upon the assumption that the chemical potentials can be neglected relative to V0 and V0,A. Exact, Hartree-Fock and density-functional values were used for the latter. The results are overall encouraging; the errors in the energies generally decrease markedly as the nuclear charges Z increase and the assumptions become more valid. Improvement is needed, however, in fitting the V0 and V0,A to Z.

Surface Energies of Nonionic Surfactants Adsorbed onto Nylon Fiber and a Correlation with Their Solubility Parameters

1992 ◽  
Vol 62 (9) ◽  
pp. 535-546 ◽  
Author(s):  
Philip E. Slade ◽  
Debra N. Hild
Keyword(s):  
Homologous Series ◽  
Nonionic Surfactants ◽  
Solubility Parameters ◽  
Nylon 66 ◽  
Synthetic Fibers ◽  
Surface Energies ◽  
Nylon Fiber

The surface energies of spin finishes adsorbed onto synthetic fibers are a major factor in determining the processing capabilities of these fibers. They also play a key role in determining how wettable the fibers are by other materials that may be applied to yarn or fabrics in later stages of processing, such as dyes, sizes, or anti-soiling agents. We have applied several homologous series of nonionic surfactants, which can be used as spin finish emulsifiers, to nylon 66 fibers and determined the polar, dispersion, and total surface energies of these adsorbed materials. We also propose a relationship between the measured surface energies and the calculated Hansen fractional solubility parameters.

scholarly journals A gateway for ion transport on gas bubbles pinned onto solids

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Veton Haziri ◽  
Tu Pham Tran Nha ◽  
Avni Berisha ◽  
Jean-François Boily
Keyword(s):  
Ion Transport ◽  
Metal Ion ◽  
Electrochemical Impedance ◽  
Gas Bubbles ◽  
Open Circuit ◽  
Double Layers ◽  
Water Geochemistry ◽  
Chemical Potentials ◽  
Pore Water Geochemistry ◽  
Electric Potentials

AbstractGas bubbles grown on solids are more than simple vehicles for gas transport. They are charged particles with surfaces populated with exchangeable ions. We here unveil a gateway for alkali metal ion transport between oxygen bubbles and semi-conducting (iron oxide) and conducting (gold) surfaces. This gateway was identified by electrochemical impedance spectroscopy using an ultramicroelectrode in direct contact with bubbles pinned onto these solid surfaces. We show that this gateway is naturally present at open circuit potentials, and that negative electric potentials applied through the solid enhance ion transport. In contrast, positive potentials or contact with an insulator (polytetrafluoroethylene) attenuates transport. We propose that this gateway is generated by overlapping electric double layers of bubbles and surfaces of contrasting (electro)chemical potentials. Knowledge of this ion transfer phenomenon is essential for understanding electric shielding and reaction overpotential caused by bubbles on catalysts. This has especially important ramifications for predicting processes including mineral flotation, microfluidics, pore water geochemistry, and fuel cell technology.

scholarly journals More on complex Sachdev-Ye-Kitaev eternal wormholes

2021 ◽  
Vol 2021 (3) ◽  
Author(s):  
Pengfei Zhang
Keyword(s):  
Black Hole ◽  
Ground State ◽  
Effective Action ◽  
Chemical Potential ◽  
Specific Charge ◽  
Zero Temperature ◽  
Small Coupling ◽  
Chemical Potentials ◽  
Quench Dynamics ◽  
Two Sides

Abstract In this work, we study a generalization of the coupled Sachdev-Ye-Kitaev (SYK) model with U(1) charge conservations. The model contains two copies of the complex SYK model at different chemical potentials, coupled by a direct hopping term. In the zero-temperature and small coupling limit with small averaged chemical potential, the ground state is an eternal wormhole connecting two sides, with a specific charge Q = 0, which is equivalent to a thermofield double state. We derive the conformal Green’s functions and determine corresponding IR parameters. At higher chemical potential, the system transit into the black hole phase. We further derive the Schwarzian effective action and study its quench dynamics. Finally, we compare numerical results with the analytical predictions.

Measurement, analysis and prediction of amoxicillin oral dose stability from integrated molecular description approach and accelerated predictive stability (APS)

2020 ◽  
Vol 0 (0) ◽  
Author(s):  
Camille Merienne ◽  
Chloe Marchand ◽  
Samira Filali ◽  
Damien Salmon ◽  
Christine Pivot ◽  
...  
Keyword(s):  
Oral Dose ◽  
Shelf Life ◽  
Chromatographic Analysis ◽  
Water Adsorption ◽  
Degradation Mechanism ◽  
Oral Dosage ◽  
Hydroxyl Groups ◽  
Humid Atmosphere ◽  
Intramolecular Hydrogen ◽  
The Impact

AbstractBackgroundStability of low amoxicillin oral dosage form (5 mg) used in reintroduction drug test was not fully documented. Furthermore, the impact of (1) salt moiety of amoxicillin and (2) amoxicillin – excipient interactions upon the antibiotic formulation stability during the storage was not characterized so that the estimation of the pharmaceutical expiration date from shelf-life was uncertain. Thus, the main goal of this study was to estimate the shelf-life of two formulations of amoxicillin, using a semi-predictive methodology.MethodsAmoxicillin sodium (AS) and amoxicillin trihydrate (ATH), corresponding to 5-mg amoxicillin, were compounded with microcrystalline cellulose (MCC) in oral hard capsules which were, then, submitted to four environmental conditions (25 °C / 60% or 80% relative humidity (RH); 40 °C / 75% RH; 60 °C / 5% RH) in climatic chambers for 45 and 84 days. Therefore, the characterization of amoxicillin-MCC mixture was assessed by attenuated total reflectance Fourier-transform infrared spectroscopy (ATR-FTIR) The profiles of amoxicillin content (determined by stability indicating chromatographic method) as a function of storage time, temperature and RH were fitted to pre-defined kinetic models performed by accelerated predictive stability (APS).ResultsATR-FTIR analysis of AS, ATH, MCC and bulk specimens stored in heated and humid atmosphere confirmed water sorption to cellulose described by a broad and unresolved 3600 to 3000 cm−1 band associated with (1) general intramolecular and intermolecular hydrogen bonding between water and hydroxyl groups of the cellulose, and with (2) free hydroxyl in cellulose. Moreover, a dramatic decrease of absorption at 1776 and 1687 cm−1 respectively characteristic of the β-lactam ring (νC=O) and amide group (νC=O), was revealed as a consequence of AS and ATH degradation caused by moisturization of bulk. Amoxicillin degradation was established by chromatographic analysis showing faster AS degradation than ATH throughout time exposure. The combined effects of temperature – RH were successfully modeled by APS, where AS and ATH showed accelerated (auto-catalysis degradation mechanism) and linear degradation, respectively. The faster AS degradation was assumed to be linked to lower hydrogen donor to hydrogen acceptor count ratio and polar surface than ATH, increasing the probability of AS hydrolysis by water adsorption to AS-MCC solid dispersion (e.g., by reduction of protective intramolecular hydrogen bonds between AS molecules). Furthermore, the compounding which involved a drastic homogenization of solids may have affected the crystalline degree of MCC with an increase of amorphous phase more sensitive to water adsorption.ConclusionsThe improvement of amoxicillin compounding for oral dose forms might be rationalized by taking into account the molecular descriptors of salt moiety and excipients, improved by the choice of an appropriate process of production, characterized from infrared vibrational spectroscopy and chromatographic analysis and finally predicted from accelerated stability assays.

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