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(11/10) Ученые из ИФХЭ РАН и МГУ под руководством Ольги Виноградовой поняли, как «полосатая» гидрофобность..
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(11/10) Ученые обнаружили пути проникновения вирусов гриппа и ВИЧ в организм
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(17/04) Курс “Анализ геномных данных”, Москва, 2 – 11 июля 2012
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(12/03) Впервые получено изображение атомов, движущихся в молекуле
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Results 21 - 30 of 134

Quantum Chemical Modeling of the Adsorption of Chloride Ion and Water Molecule on Group 1B Metals

I. V. Nechaev and A. V. Vvedenskii


Voronezh State University, Universitetskaya pl. 1, Voronezh, 394006 Russia

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Received July 7, 2008


Abstract — Quantum chemical modeling (at DFT-B3LYP level) of the adsorption of Clframe0 and H2O particles on top and into hollow sites of defect-free low index faces of copper, silver, and gold simulated by n-atomic clusters with n = 9 to 17 is carried out. The validity of simulations is confirmed by the comparison to the available literature data on the work function of the metals and the calculated gas-phase adsorption of chlorine. Relative effects of the chemical (metal nature), macrostructural (crystal face), and coordination (adsorption site) factors on the parameters of the chemisorption bond and molecular characteristics of the adsorbate and adsorbent, namely, the frame1ads adsorption energy at frame2 = 0K, R(Meframe3Clframe4) and R(Me–O) adsorption bond lengths, Q effective charges of chlorine atom and water molecule, O–H distance and frame5frame6frame7 angle in frame82frame9 molecule, deviation of the H2O dipole moment vector from normal orientation to the cluster surface, and frame10frame11frame12frame13frame14 energies of the highest occupied molecular orbital of frame15frame16n, [MenCl]frame17, MenH2O, and [MenClH2O]frame18 clusters, are considered. The inner hydration shell of Clframe19 is shown to involve six water molecules, the most stable configuration of (frame202frame21)6 cluster being prism-like. An electron density shift from chlorine and water molecule to the metal cluster is found to accompany the adsorption and be more pronounced in the case of anion. The character of differences in the hydrophilicity of the group 1B metals and their diverse crystal faces is discussed. The role of hydration effects in the chemisorption of chloride ion on copper, silver, and gold is analyzed in terms of the continuum, molecular, and combined molecular–continuum models.

PACS numbers: 68.43.-h


DOI: 10.1134/S2070205109020026
10/04/2009 | 1081 Hits | Print


Critical Phenomena at Electrosorption of Organic Compounds on Electrodes

R. N. Kuklin


Frumkin Institute of Physical Chemistry and Electrochemistry, Russian Academy of Sciences,
Leninskii pr. 31, Moscow, 119991 Russia

Received June 5, 2008


Abstract - Problems associated with the effect of surfactants on polarization characteristics of a liquid metal electrode–electrolyte interface, as well as the fluctuations of its adsorption coverage, are considered. For the effective adsorption potential, the analytical dependence of which on the state parameters is determined by a nonequilibrium surface pressure, an expression derived earlier in terms of a quasichemical approximation is proposed. It is shown that the excessive differential capacitance of the interface, associated with the specific adsorption of surfactants, turns to infinity on the spinodal. The relaxation and correlation of equilibrium fluctuations of the adsorption process completeness in the interface plane at different electrode potentials are studied. Expressions for the correlation length of fluctuation are obtained. Their fundamental importance as the natural scale for the size and the duration of a nanochemical process is discussed. It is shown that the relaxation time and the correlation radius of fluctuations turn to infinity at the adsorption phase stability limit.


PACS numbers: 68.43.-h

DOI: 10.1134/S2070205109020038
10/04/2009 | 1096 Hits | Print


Adsorption of Hexane and Benzene on Fluorinated Silicas: The Effect of the Perfluoralkyl Chain Length

T. M. Roshchina*, N. K. Shoniya*, A. B. Nikol’skaya*, M. S. Lagutova*, and A. Yu. Fadeev**


*Moscow State University, Faculty of Chemistry, Vorob’evy Gory, Moscow, 119992 Russia

**Department of Chemistry and Biochemistry, Seton Hall University, South Orange, New Jersey, 07079 USA

Received June 5, 2008


Abstract — By means of the gas chromatography and a static adsorption method, the extent of fluorination of the carrier surface, determined by the length of the grafted radical chain, affects the adsorption properties of silicas with perfluorohexyl, perfluoropropyl, and trifluoromethyl coatings. The analysis of data on the original carrier and chemically hydrophobized silicas, including a sample with grafted octyl groups used as the reference, shows that modification leads to the decrease in both the adsorption (a at 298 K and the Henry constants (KH) in a wide temperature range for hexane and benzene. However, in contrast to silicas with perfluoropropyl or perfluorohexyl coatings, the a and KH values on trifluorometylsilica became equal (n-alkanes) or even somewhat lower (aromatic hydrocarbons) than those observed on the non-polar octylsilica surface. Irrespective of the degree of fluorination of the silica surface, the substitution and screening of silanol groups in silica lead to weakening the polarity of polyfluoroalkylsilicas as compared with the original carrier.


PACS numbers: 68.43.-h

DOI: 10.1134/S207020510902004X
10/04/2009 | 1179 Hits | Print


Calculations of the Similarity Factor and Initial Adsorption Heats of Substances on LiX, NaX, and KX Zeolites

V. P. Kolganov


Russian State Agriculture University—Timiryazev Agricultural Academy, Kaluga Branch, Kaluga, Russia

Received June 5, 2008


Abstract — Based on an electrostatic model, the energies interaction between substances with different electron structures on one hand, and the LiX, NaX, and KX zeolites, on the other hand, as well as the similarity factors of characteristic adsorption curves of substances, are calculated.

PACS numbers: 68.43.-h


DOI: 10.1134/S2070205109020051
10/04/2009 | 1213 Hits | Print


DFT Modeling of the Adsorption of Benzene, Methanol, and Ethanol Molecules in Activated Carbon Nanopores

A. M. Tolmachev, D. A. Firsov, T. A. Kuznetsova, and K. M. Anuchin


Chemistry Department, M.V. Lomonosov Moscow State University, Leninskie Gory, Moscow, 119991 Russia

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Received June 9, 2008


Abstract — Changes in energetic and structural characteristics of benzene, methanol, and ethanol molecules at their adsorption in nanosize slit-like pores of active carbon are estimated in quantum chemical calculations in the density functional approximation. The most energetically favorable arrangement of benzene molecules is found to be that when the molecular planes are parallel to each other and to the nanopore walls. Alcohol molecules are predominantly arranged so that C–O and C–C bonds are nearly parallel to the nanopore walls, while O–H bond is directed toward the nearest wall. At the adsorption of two alcohol molecules, they form a hydrogen bond and their skeletons are also parallel to the nanopore wall.


PACS numbers: 68.43.-h

DOI: 10.1134/S2070205109020063
10/04/2009 | 1194 Hits | Print


Bridge Polysilsesquioxane Xerogels with a Bifunctional Surface Layer of the frame0Si(CH2)3NH2/frame1Si(CH2)3SH Composition

N. V. Stolyarchuk*, I. V. Mel’nik, Yu. L. Zub*, M. Barczak**, A, Dabrowski**, and B. Alonso***


*Chuiko Institute of Surface Chemistry, National Academy of Sciences of Ukraine,
ul. Generala Naumova 17, Kiev, 03164 Ukraine

**Faculty of Chemistry, University of Maria Curie-Sklodowska, Pl. M. Curie-Sklodiwskiej 3, Lublin, 20-031 Poland

***Institute Charles Gerhardt – UMR 5253 (CNRS/ENSCM/UM2/UM1) 8, rue de l’Ecole Normale,
Montpellier cedex 5, 34296 France

Received June 5, 2008

Abstract — Xerogels with a bifunctional surface layer of the Si(CH2)3NH2/Si(CH2)3SH composition are synthesized by hydrolytic co-polycondensation of bis(triethoxy)silane (C2H5O)3Si(CH2)2Si(OC2H5)3 and two trifunctional silanes, namely, 3-aminopropyltriethoxysilane and 3-mercaptopropyltrimethoxysilane. Using IR, 1HMAS NMR, and 13C CP/MAS NMR spectroscopic techniques, it is shown that in addition to complexing groups, the surface layer also contains water, silanol groups that are involved in the hydrogen bond formation and also residual ethoxysilyl groups. According to 29SiCP/MAS NMR spectroscopic data, the degree of polycondensation of synthesized xerogels exceeds 80%. It is found that the use of 1,2-bis(triethoxysilyl)ethane as the structuring agent in place of tetraethoxysilane allows one to synthesize bifunctional xerogels with the highly developed biporous structure (Ssp = 607–680 m2/g, Vc = 1.38–1.47 cm3/g, d = 2.9–3.1 and 18.3 nm). Changing the ratio structuring-silane/functionalizing-silane-mixture from 2 : 1 to 4 : 1 in the reaction system has virtually no effect on the porous structure parameters of final xerogels.


PACS numbers: 68.43.-h

DOI: 10.1134/S2070205109020075
10/04/2009 | 1234 Hits | Print


Sorption Processes in the Nanostructures of Mesomorphous Polymers

S. F. Grebennikov, Yu. S. Chulkova, and E. I. Zaitseva


State University of Technology and Design, Bol’shaya Morskaya ul. 18, St. Petersburg, 191065 Russia

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Received June 5, 2008


Abstract — A correlation between the coefficients of the thermal equation of the vapor absorption by polymers and the parameters of the molecular and supramolecular structures of the polymers is analyzed.

PACS numbers: 68.43.-h

DOI: 10.1134/S2070205109020087
10/04/2009 | 1209 Hits | Print


Chemical and Phase Composition of Nanosized Oxide and Passive Films on Niframe0Cr Alloys. II. XPS Analysis of Films Produced by Anodic Passivation of Alloys in 1 N H2SO4


Yu. Ya. Andreev, E. A. Skryleva, and I. A. Safonov

Moscow State Institute of Steel and Alloys, Leninskii pr. 4, Moscow, 119991 Russia

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Received July 18, 2008


Abstract — XPS data of thin (1 to 2 nm) oxide films formed by the anodic passivation of Ni–2 at % Cr and Ni6at % Cr alloys in 1 N H2SO4 are discussed. Thermodynamic calculations of the solid-phase chemical reaction 3NiO + 2Cr = Cr2O3 + 3Ni are carried out taking into account the changes in the surface energy at the alloyoxide film interface along with the Gibbs energy change in the alloy oxidation reaction.


PACS numbers: 81.07.-b

DOI: 10.1134/S2070205109020099
10/04/2009 | 1158 Hits | Print


Static and Dynamic Models of the Structure of Magic Silver Nanoclusters


D. L. Tytik

Frumkin Institute of Physical Chemistry and Electrochemistry, Russian Academy of Sciences,
Leninskii pr. 31, Moscow, 119991 Russia

Received August 13, 2008


Abstract — The relationship between static and dynamic models of the nanoparticle structure is considered based on the analysis of magic properties of silver clusters (results of molecular dynamics experiments). Dynamics of silver nanoclystals with cuboctahedral morphology in the nanosize range is characterized by the cooperative motion of atoms in the layers equidistant from the nanoparticle mass center. In this case, the cub-octahedral nanoparticles pass in a more stable icosahedral shape. The motion of atoms in a stable icosahedral cluster passes into a stationary oscillation mode (diffusion is absent). The distribution of middle positions around which atoms in a cluster oscillate suggests that the clusters simultaneously exhibit the properties of a liquid (reduced density that approaches the melt density) and a solid. The clusters have the regular non-crystalline structure (the shells of atoms equidistant from the cluster center form the Platonic and Archimedean bodies).


PACS numbers: 61.43.Bn, 61.50. Ah

DOI: 10.1134/S2070205109020105
10/04/2009 | 1170 Hits | Print


Developing the Synthesis of Homogeneously Microporous Carbon Membranes for Selective Extraction and Accumulation of Organic Molecules with a Carbon Unit as a Carrier


V. A. Drozdov*, O. N. Baklanova, V. A. Likholobov*, O. A. Chirkova, and T. I. Gulyaeva

* Omsk Scientific Center, Siberian Division, Russian Academy of Sciences, Omsk, Russia

Institute of Problems of Hydrocarbon Processing, Siberian Division, Russian Academy of Sciences,
ul. Neftezavodskaya 54, Omsk, 644040 Russia

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Received June 5, 2008


Abstract — The composite carbon–carbon membranes (CMS membranes) obtained by polymer modification of a mesoporous carbon substrate through the formation of an activated carbon layer have microporous structures (specific micropore volume 0.11 0.05 cm3/g). The size distribution of micropores shows two distinct peaks at 4.5 to 6.5 and 7.0 to 9.0 Å. The micropores with these widths adsorb well CO2 and frame0frame14, respectively.


PACS numbers: 68.43.-h

DOI: 10.1134/S2070205109020117
10/04/2009 | 900 Hits | Print


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