Search results for "Kinetics"
showing 10 items of 2224 documents
Superparamagnetic recoverable flowerlike Fe3O4@Bi2O3 core–shell with g-C3N4 sheet nanocomposite: synthesis, characterization, mechanism and kinetic s…
2019
In the present research study, a simple method was developed for the synthesis of three-dimensional flowerlike Fe3O4@Bi2O3 core–shell with g-C3N4 sheet nanocomposites. The X-ray diffraction, Fourier transform infrared spectroscopy, scanning electronic microscopy, transmission electron microscope, vibrating sample magnetometer, dynamic laser scattering analyzer and UV–Vis diffuse reflection spectroscopy were employed for the characterization of structure, purity and morphology of the resultant samples. The degradation of indigo carmine as a model of organic dye pollutant is applied for photo-catalytic activity. The parameters which are affecting the efficiency of various parameters, such as;…
Peculiarities of the diffusion-controlled radiation defect accumulation kinetics under high fluencies
2020
We are grateful to A. Lushchik and E. Shablonin for numerous and valuable discussions. This work has been carried out within the framework of the EUROfusion Consortium and has received funding from the Euratom research and training programme 2014-2018 and 2019-2020 under grant agreement No 633053. The views and opinions expressed herein do not necessarily reflect those of the European Commission. The raw/processed data required to reproduce these findings cannot be shared at this time as the data also forms part of an ongoing study.
Thermal annealing of radiation damage produced by swift 132Xe ions in MgO single crystals
2020
Abstract The annealing kinetics of the electron-type F+ and F color centers in highly pure MgO single crystals irradiated by 0.23-GeV 132Xe ions with fluences covering three orders of magnitude (Φ = 5 × 1011 –3.3 × 1014 ions/cm2) are studied experimentally via dependence of the optical absorption on preheating temperature. The annealing data are analyzed in terms of the diffusion-controlled bimolecular reactions between F-type centers and complementary interstitial oxygen ions. The behavior of the main kinetic parameters – the migration energies and pre-exponential factors – for different irradiation fluences is discussed and compared with that for other wide-gap binary materials from previ…
The peculiarities of the radiation damage accumulation kinetics in the case of defect complex formation
2020
Abstract The kinetics of radiation defect accumulation under irradiation by heavy particles is theoretically analysed under the assumption of defect complex genesis, particularly, the ones of anion and cation vacancies. The obtained analytical mathematical model and revealed peculiarities of radiation dose dependencies can be used for analysis of the experimental results for different crystalline materials for solid-state electronics and photonics.
Sub-nanosecond excitonic luminescence in ZnO:In nanocrystals
2019
The financial support of research European Union ERA.NET RUS_ST20170-51 . This work was partly supported by Russian Foundation for Basic Research, Russia , project No. 18-52-76002 . The sample preparation was carried out as part of SFERA II project -Transnational Access activities ( European Union 7th Framework Programme Grant Agreement N3126430 ).
Nanoscale Etching of GaAs and InP in Acidic H<sub>2</sub>O<sub>2</sub> Solution: A Striking Contrast in Kinetics and Surface …
2018
In this study of nanoscale etching for state-of-the-art device technology the importance of the nature of the surface oxide, is demonstrated for two III-V materials. Etching kinetics for GaAs and InP in acidic solutions of hydrogen peroxide are strikingly different. GaAs etches much faster, while the dependence of the etch rate on the H+ concentration differs markedly for the two semiconductors. Surface analysis techniques provided information on the surface composition after etching: strongly non-stoichiometric porous (hydr)oxides on GaAs and a thin stoichiometric oxide that forms a blocking layer on InP. Reaction schemes are provided that allow one to understand the results, in particular…
Quasi-RRHO approximation and DFT study for understanding the mechanism and kinetics of nitration reaction of benzonitrile with nitronium ion
2021
Abstract The nitration reaction of benzonitrile with nitronium cation, NO2+, has been studied within the Molecular Electron Density Theory at the MN15-L/aug-cc-pVTZ level of theory. For this electrophilic aromatic substitution (EAS) reaction, three regioisomeric reaction paths have been studied. Quasi-RRHO approximation was applied to consider the vibrational contribution to entropy and correct the Gibbs free energy profile of the reaction in the solvent phase. Benzonitrile is less nucleophilically activated than benzene due to the presence of the electron-withdrawing CN group the meta position is the more favorable reaction path of this EAS reaction. The analysis of ELF and AIM demonstrate…
Unexpected Substituent Effects in the Iso-Heterocyclic Boulton-Katritzky Rearrangement of 3-Aroylamino-5-methyl-1,2,4-oxadiazoles: A Mechanistic Stud…
2019
The kinetics of the iso-heterocyclic mononuclear rearrangement of some 3-aroylamino-5-methyl-1,2,4-ozadiazoles was carefully examined under largely variable acidic or alkaline conditions. This reaction may proceed via two different mechanistic pathways (an uncatalyzed and a base-catalyzed one), as accounted for also by the evaluation of the relevant activation parameters. Substituent effects, as quantified by means of the Hammett’s equation, appear relatively modest; however, they reveal some interesting anomalies, which enabled us to draw a very precise picture of the intimate reaction course.
Unravelling the kinetics and molecular mechanism of the degenerate Cope rearrangement of bullvalene
2020
The kinetics and molecular mechanism of the gas phase degenerate Cope rearrangement (DCR) of bullvalene have been investigated by applying quantum mechanical calculations. Highly accurate energies (CBS-QB3 and CBS-APNO) and RRKM calculations were employed to study the kinetics and ‘fall-off’ behavior. It was found that the DCR of bullvalene (C3v) occurs through a bishomoaromatic transition structure (C2v) with an energy barrier of ∼49 kJ mol−1. The calculated activation energy and enthalpy were in good agreement with the available values in the literature, but lower than those of common Cope rearrangement; this result is related to the high stabilization energy due to the interaction of the…
Heavy enzymes and the rational redesign of protein catalysts
2019
Abstract An unsolved mystery in biology concerns the link between enzyme catalysis and protein motions. Comparison between isotopically labelled “heavy” dihydrofolate reductases and their natural‐abundance counterparts has suggested that the coupling of protein motions to the chemistry of the catalysed reaction is minimised in the case of hydride transfer. In alcohol dehydrogenases, unnatural, bulky substrates that induce additional electrostatic rearrangements of the active site enhance coupled motions. This finding could provide a new route to engineering enzymes with altered substrate specificity, because amino acid residues responsible for dynamic coupling with a given substrate present…