Search results for "physical chemistry"

Vibrational spectroscopy of trans and cis deuterated formic acid (HCOOD): Anharmonic calculations and experiments in argon and neon matrices

2010

The absorption spectra of trans and cis conformers of deuterated formic acid (HCOOD) isolated in argon and neon matrices are analyzed in the mid-infrared and near-infrared spectral regions (7900–450 cm � 1 ). Vibrational excitation by narrow-band IR radiation is used to convert the lower-energy trans conformer to the higher-energy cis form. A large number of overtone and combination bands are identified. The results of anharmonic vibrational calculations (CC-VSCF) for both conformers are reported and compared to the experimental spectra.

Adsorption on a stepped substrate.

1994

Donor and acceptor substituted triphenylamines exhibiting bipolar charge-transporting and NLO properties

2017

Donor-acceptor type triphenylamine-based malonodinitriles were synthesized and their thermal, optical, photophysical, electrochemical and nonlinear optical properties were studied. The synthesized compounds formed glasses with the glass transition temperatures ranging from 38 to 107 °C. The ionization potentials of the samples of the compounds established by cyclic voltammetry were found to be in the range of 5.50–5.57 eV, while those estimated by photoelectron emission spectrometry ranged from 5.36 to 5.74 eV. The electron affinity values of the compounds were found to be in the range of −3.41–−3.05 eV. The ambipolar charge-transporting properties were observed for the layers of triphenyla…

Benzene monitoring by micro-machined sensors with SnO2 layer obtained by using micro-droplet deposition technique

2011

International audience; SnO2 thin layers were deposited by the way of the micro-droplet technique. The sensor substrate consisted of a thin membrane developed on oxidised silicon wafer. The sensing layers were deposited by means of the micro-droplet technique into thin layers of about 100 nm. Such devices were tested for benzene detection. The obtained results showed a very high sensitivity for this chemical compound since 500 ppb were detected. The results presented in this paper were not focused on the reactional mechanism of benzene detection but rather on the development of a cheap and sensitive sensor using sol-gel and micro-droplet processes. Since these layers were elaborated using s…

Ab initio calculations of MgF2 (001) and (011) surface structure

2010

We present the results of calculations of surface relaxations, rumplings, and charge distribution for the MgF2 (0 0 1) and (0 1 1) surfaces using ab initio code Crystal-2003 and the hybrid exchange-correlation B3PW functional. These two neutral and polar surfaces show very small relaxation and negligible increase of covalent contribution to the chemical bonding thus remaining considerably ionic. The calculated bulk optical band gap is in a good agreement with the experimental value, whereas optical band gap for the polar (0 1 1) surface is reduced by 0.6 eV compared with the calculated bulk value, in contrast to the (0 0 1) surface gap which remains very close to the bulk.

Structural features of selected protic ionic liquids based on a super-strong base

2019

Protic ionic liquids (PIL) were prepared from a super-strong base 1,7-diazabicyclo[5.4.0]undec-7-ene (DBU) and super-strong acids, trifluoromethane sulfonic acid (TfOH), and (trifluoromethanesulfonyl)-(nonafluorobutylsulfonyl)imide, (IM14H), ([DBUH][TfO] and [DBUH][IM14], respectively; the latter for the first time) and their chemical and physical properties and structural features have been explored using a synergy of experimental and computational tools. The short range order in neat DBU, as well as the long range structural correlations induced by charge correlation and hydrogen bonding interactions in the ionic liquids, have been explored under ambient conditions, where these compounds …

11B-MAS NMR approach to the boron adsorption mechanism on a glucose-functionalised mesoporous silica matrix

2018

[EN] Boron chemistry has raised much interest because, despite the difference between necessities and toxicity being very narrow, it is still widely used in industrial processes. In a previous work we reported an adsorbent for boron extraction from water by the functionalisation of a UVM-7 mesoporous silica matrix with gluconamide moieties. The ability of this material to adsorb boron is based on its well-known affinity for coordinating the cis-diols present in attached saccharide. Although much research on the formation of boron esters with sugars and sugar derivatives in solution has been done, very few reports have dealt with the adsorption mechanism of boron onto functionalised material…

The influence of molecular properties of additives on the stability of polyethylene in high electric fields

2003

Results are presented of studies of some molecular properties, i.e., dipole moment, total polarizability, and electronic polarizability, of dihalide and diamine derivatives of phenylene, p,p'-bi-phenylene and carbazole, which are used as additives for physical modification of polyethylene. The diffusion coefficients of these substances from a polyethylene matrix were estimated, and the stability of modified polyethylene in high electric fields (50 Hz) was found. The mechanism of action of high-voltage stabilizers in polyethylene was verified. >

Nitrogen Hydrate Cage Occupancy and Bulk Modulus Inferred from Density Functional Theory-Derived Cell Parameters

2021

International audience; Gas clathrate hydrate solid materials, ubiquitous in nature as found either on the ocean floor, permafrost on the Earth, or in extraterrestrial planets and comets, are also technologically relevant, for example, in energy storage or carbon dioxide sequestration. Nitrogen hydrate, in particular, is of great interest as a promoter of the kinetics of the methane replacement reaction by carbon dioxide in natural gas hydrates. This hydrate may also appear in the chemistry of planets wherever nitrogen constitutes the majority of the atmosphere. A fine understanding of the stability of this hydrate under various thermodynamic conditions is thus of utmost importance to asses…

A Grand Canonical Monte Carlo Study of the N2, CO, and Mixed N2–CO Clathrate Hydrates

2018

In this paper we report the use of Grand Canonical Monte Carlo (GCMC) simulations to characterize the competitive trapping of CO and N2 molecules into clathrates, for various gas compositions in the temperature range from 50 to 150 K. The simulations evidence a preferential trapping of CO with respect to N2. This leads to the formation of clathrates that are preferentially filled with CO at equilibrium, irrespective of the composition of the gas phase, the fugacity, and the temperature. Moreover, the results of the simulations show that the small cages of the clathrate structure are always filled first, independent of either the guest structure or the temperature. This issue has been associ…