摘要:

AbstractIt was found that level of structural substance organization, amount of embodied information, and consequently, substance properties are determined by the degree of the substance polyatomicity. This substantiates the fact that both covalent and noncovalent supermolecular individuals, which are the matter of the chemistry of highly organized compounds, fulfil the same general chemical but different specific regularities. Among the former there is extended Prust's law, which was re‐established by the fact of production and identification of solids with the constant composition. It was also found that formation of any individuals is due to production and realization of a certain amount of information sufficient for their structural organization. Chemical modeling of biosynthesis was chosen as the common approach for developing the processes of production and realization of information. It was shown that well‐known processes of chemical buildup (CB) and molecular self‐assembling (MSA) are those chemical models. The application of announced regularities has opened up a new perspective to create chemical‐information technology (CIT), allowing us to produce material resources making no perturbations in the planet ec

ISSN:1022-1360    

DOI:10.1002/masy.19981360103

出版商:WILEY‐VCH Verlag GmbH&Co. KGaA    

年代:1998

数据来源: WILEY

摘要:

AbstractTwo types of chemically modified silica gels with covalently bonded hydrophobic (alkyl, SiO2‐C8) and hydrophilic (aminoalkyl, SiO2‐NH2) groups were studied by dielectric relaxation method. For SiO2‐C8two relaxation maxima were detected at 140 and 238K. From comparison with bulk silica the lower temperature maximum was assigned to cooperative re‐orientation of residual silanols and higher one to melting of physically adsorbed water. Both maxima are much weaker for SiO2‐C8then for bulk silica. In Arrhenius coordinates relaxation at 238K exhibits similar behavior as OH groups in polyvinyl alcohol and so it was assigned to mobility of orientation defects in mono‐dimensional chain of physically adsorbed water. For SiO2‐NH2no low temperature relaxation effect was observed. Intensive relaxation was measured at 248 K only. Strong interaction between supramolecules of silanol groups, bonded aminogroups and adsorbed wate

ISSN:1022-1360    

DOI:10.1002/masy.19981360104

出版商:WILEY‐VCH Verlag GmbH&Co. KGaA    

年代:1998

数据来源: WILEY

摘要:

AbstractUltrafine lead sulfide clusters are produced by the reaction of long‐chain thiols with lead ions in non‐aqueous medium, and according to X‐ray diffraction (XRD) data reveal the different steps of he bulk‐like rocksalt lattice growth. XRD pattern is simulated by the Debye formula for four model clusters (27, 75, 125, 729 atoms) and the correspondence of model and experimental clusters is shown that allows to estimate their size.Ab initioMOLCAO calculations result in energetical parameters and charge distribution for the clusters with 27 atoms. The value of energy gap indicates the true tendency of variation for the clusters of different size but left yet higher than maxima in the optical absorption at the fixe

ISSN:1022-1360    

DOI:10.1002/masy.19981360105

出版商:WILEY‐VCH Verlag GmbH&Co. KGaA    

年代:1998

数据来源: WILEY

摘要:

AbstractA computational method for the band structure of nanowires having approximately cylindrical symmetry is developed. The effective one‐electron potential is supposed to have spherical symmetry in the region of the atomic centres and is assumed to be constant in the interstitial region. The corresponding electronic density is supposed to be localised inside the region of cylindrical shape. The base wave functions are obtained by sewing together solutions of the Schrödinger equation for an electron in the empty cylinder (cylindrical waves) with spherically symmetrical solutions for the muffin‐tin spheres. Under the condition of the continuity of the base functions and their first derivatives overlap integrals and Hamiltonian matrix elements are obtained. Dispersion curves and electronic densities of states for chains of transition metals and those of nanowires from metals from K to Zn are calcul

ISSN:1022-1360    

DOI:10.1002/masy.19981360106

出版商:WILEY‐VCH Verlag GmbH&Co. KGaA    

年代:1998

数据来源: WILEY

摘要:

AbstractA comparative study of DNA interaction with different counterions in solution has been conducted by the following methods: flow birefringence (FB), low‐gradient viscometry, circular dichroism (CD), and UV‐spectroscopy. The influence of counterions on the persistence length and polyelectrolyte swelling of DNA has been investigated. The process of DNA packing during the interaction with trivalent ions in solution has been studied, as well as the influence of Mn2+on the binding of trivalent ions with

ISSN:1022-1360    

DOI:10.1002/masy.19981360107

出版商:WILEY‐VCH Verlag GmbH&Co. KGaA    

年代:1998

数据来源: WILEY

摘要:

AbstractThe work is focused on the preparation and characterisation of rare‐earth containing stearic acid Langmuir‐Blodgett (LB) films. Stearic acid monolayer behavior on the rare‐earth containing aqueous subphase have been analyzed by thermodynamic measurements. The compression isotherm shape changed substantially under varying the anion type at the constant rare‐earth cation content in aqueous subphase. The structure of formed multilayer rare‐earth containing LB films was studied using small angle X‐rays diffraction. The considerable structural defects in multilayer films were found when rare‐earth chloride solution was exploited as aqueous subphase, caused presumably by electrostatic interactions at the monolayer surface under high binding of rare‐earth cations. The use of monodentate complexones like acetic acid was proposed to form bulk phase quasi‐neutral rare‐earth complexes. The electroneutral ligand exchange reactions of such complexes with stearic acid monolayer allowed to neutralise monolayer surface under rare‐earth cations binding and to form condenced monolayer below the triple‐point temperature. The compression of such monolayer to the state of minimal compressibility and subsequent monolayer deposition resulted in the formation of high ordered LB films with high content of adsorbed multivalent rare‐earth cations arranged in two‐di

ISSN:1022-1360    

DOI:10.1002/masy.19981360108

出版商:WILEY‐VCH Verlag GmbH&Co. KGaA    

年代:1998

数据来源: WILEY

摘要:

AbstractSurface nano‐size structures have been obtained by supporting on oxide supports (SiO2, MgO, Al2O3) some cluster carbonyls of Os, Fe, Fe‐Rh and by their following thermal conversions. Surface species were characterized by IR‐spectroscopy, high‐resolution TEM, XPS, Mössbauer spectroscopy and temperature‐programmed desorption technique. Their catalytic properties was studied in CO hydrogenatio

ISSN:1022-1360    

DOI:10.1002/masy.19981360109

出版商:WILEY‐VCH Verlag GmbH&Co. KGaA    

年代:1998

数据来源: WILEY

摘要:

AbstractThe effect of stoichiometry on various features of III‐V compounds are investigated. It is shown experimentally that the optimum vapor pressure of V elements minimizes the deviation from the stoichiometric composition. Vapor pressure control technology is applied not only to the liquid phase epitaxy and bulk crystal growth but also to the surface reaction in molecular layer epitaxy.The surface reaction and kinetic phenomena of GaAs mono‐molecular layer growth by using chemical adsorption of Ga(CH3)3(trimethyl gallium: TMG) and arsine (AsH3) was investigated. The growth feature was strongly influenced by the surface stoichiometry of arsenic during growth. For example, the diffusion of the doped impurity is affected by the AsH3amount of supply, the diffusion was prevented by controlling the stoichiometry. The control of stoichiometry was examined systematically and was applied for the device fabrication such as ballistic transis

ISSN:1022-1360    

DOI:10.1002/masy.19981360110

出版商:WILEY‐VCH Verlag GmbH&Co. KGaA    

年代:1998

数据来源: WILEY

摘要:

AbstractOne of the most important problems of modern chemistry, both preparative and theoretical one, is the creation of organized atomic ‐ molecular assemblies i.e., atoms and molecules bound in a definite manner and interacting with each other, as a jointly, they become able to behave like an assembly, a single mechanism, to perform some functions, for example, to recognize separate molecules of environment (receptors), to transform an electromagnetic signal to electric field (photosynthetic), to memorize (memory cell), catalyze function and others.The chemistry of preceding period had been developing as the science of properties and transformations of individual compounds and substances. At present the progress in the notion of the nature of chemical bonds, a new level of understanding of the chemical reactions mechanism, the knowledge of the regularities of nonstationary states in reactive media and the data on the at processes interfaces have determined the up to day problem of organized molecular assemblies with a required functionality.Thermal oxidation of silicon crystals which is the key process in the technology of integral circuits production can be represented, in its main features, by the mechanism of semiconductor dissolving in the condensed phase. A characteristic feature of silicon oxidation is that the silicon activation energy of the limiting stage is lower than that of the formation of gas ‐ phase monoxide, difference being the energy of siloxane net reorganization in silicon dioxide. The analysis shows that within the row of possible systems semiconductor ‐ dielectric, it is silicon ‐ silicon dioxide that is distinguished by a maximum self ‐ organizing effect. This is one of the main reasons why only silicon could be chosen among large number of semiconductor substances for use in the technology of integral circuits.A molecular system of amphiphilic long ‐ chain molecules, obtained according to the Langmuir ‐ Blodgett method is an example of simplest assembly on the basis of which the elements of gas sensors can be prepared, as well as the systems of quantum dots, the objects of the low ‐ dimension physics.We have investigated assemblies constructed from multimolecular compositions using the Langmuir ‐ Blodgett technique and thin ‐ layer systems based on glassy and amorphous silica films with fragments of organic molecules introduced into the matrix.Molecular engineering is a new level of the modern preparative chemistry; moreover, it is a system of concepts introducing a new culture in technology. In this sense, it is most important to realize the evolution principle in the strategy

ISSN:1022-1360    

DOI:10.1002/masy.19981360111

出版商:WILEY‐VCH Verlag GmbH&Co. KGaA    

年代:1998

数据来源: WILEY

摘要:

AbstractWe report on the recently developed method for the synthesis, optical, and structural properties of CdSe and CdTe nanocrystals. They were formed in aqueous solutions at moderate temperatures by a wet chemical route in the presence of thiol molecules as effective stabilizing agents. The size‐selective precipitation technique was applied for the post‐preparative nanoparticle fractionation into a series of CdSe and CdTe nanocrystals with extremely narrow size distributions exhibiting mean cluster sizes in the range of 2 to 4 nm. The nature of stabilizing agent (mercaptoalcohols and mercaptoacids) had an important influence on the particle size and determines largely the photoluminescence properties. The nanocrystals were characterized by means of UV‐vis absorption and photoluminescence spectroscopy, X‐ray diffraction, and high resolution transmission electron microscopy

ISSN:1022-1360    

DOI:10.1002/masy.19981360112

出版商:WILEY‐VCH Verlag GmbH&Co. KGaA    

年代:1998

数据来源: WILEY