RAS Frumkin Institute of Physical Chemistry and Electrochemistry
RAS Frumkin Institute of Physical Chemistry and Electrochemistry
Dolinnyi A.I.,RAS Frumkin Institute of Physical Chemistry and Electrochemistry
Journal of Physical Chemistry C | Year: 2015
Using a generalized multiparticle Mie theory, we calculated the optical properties of gold nanoparticle (Au NP) pairs of 8-80 nm in diameter (D) and 0.1-120 nm in interparticle gap (s) under typical experimental conditions: an unpolarized incident light and random orientation of the pairs in space. By analyzing the extinction spectra of coupled spheres, three ranges of interparticle separations (long, middle and short) with different plasmon coupling regimes were distinguished. For long interparticle distances, a single plasmon peak in the spectrum at wavelength λp red-shifts exponentially relative to that of an isolated particle at wavelength λ0 as a function of x = s/D: Δλ/λ0 = (λp - λ0)/λ0 = a exp(-x/t), with a decay constant (t = 0.19) being nearly independent of nanoparticle diameters at D < 50 nm. Stronger shifts (0.04 < a < 0.08) are observed for 30-60 nm Au NPs. In the middle distance range (0.02 < s/D < (s/D)split), the extinction spectra of dimers have two plasmon peaks: transverse and longitudinal. The shift of long-wavelength peak can be reasonably approximated by the equation Δλ/λ0 = a0 + a1 exp(-x/t1), where the parameters a1 (= 0.352) and t1 (= 0.032) do not depend on the nanoparticle sizes, and a0 increases with particle size. The boundary between the long and middle interparticle distance ranges, (s/D)split, strongly varies with the Au NP diameter. At s/D < 0.02, the birth and evolution of third plasmon peak that is located between the transverse and longitudinal peaks has a strong effect upon the spectral properties of closely coupled NPs. Now the fractional shift of the longitudinal peak obeys the equation Δλ/λ0 = a0 + a1 exp(-x/t1) + a2 exp(-x/t2), where t2 = 0.004 and a2 = 0.643. The constancy of coefficients ai and ti for Au NPs of different sizes means that the fractional shifts of plasmon resonances of coupled pairs corrected by parameter a0 have to fall on a common curve. The obtained results clearly point that the Au NPs pairs can be used as the highly sensitive instruments to measure both absolute distances and their changes in the nanometric range of lengths. © 2015 American Chemical Society.
Krishtalik L.I.,RAS Frumkin Institute of Physical Chemistry and Electrochemistry
Biochimica et Biophysica Acta - Bioenergetics | Year: 2011
A low static dielectric permittivity of proteins causes the low reorganization energies for the charge transfer reactions inside them. This reorganization energy does not depend on the pre-existing intraprotein electric field. The charge transferred inside the protein interacts with its aqueous surroundings; for many globular proteins, the effect of this surroundings on the reorganization energy is comparable with the effect of reorganization of the protein itself while for the charge transfer in the middle of membrane the aqueous phase plays a minor role. Reorganization energy depends strongly on the system considered, and hence there is no sense to speak on the "protein reorganization energy" as some permanent characteristic parameter. We employed a simple algorithm for calculation of the medium reorganization energy using the numerical solution of the Poisson-Boltzmann equation. Namely, the reaction field energy was computed in two versions - all media having optical dielectric permittivity, and all the media with the static one; the difference of these two quantities gives the reorganization energy. We have calculated reorganization energies for electron transfer in cytochrome c, various ammine-ruthenated cytochromes c, azurin, ferredoxin, cytochrome c oxidase, complex of methylamine dehydrogenase with amicyanin, and for proton transfer in α-chymotrypsin. It is shown that calculation of the medium reorganization energy can be a useful tool in analysis of the mechanisms of the charge transfer reactions in proteins. © 2011 Elsevier B.V. All rights reserved.
Belyaev A.V.,RAS Frumkin Institute of Physical Chemistry and Electrochemistry |
Vinogradova O.I.,RWTH Aachen
Physical Review Letters | Year: 2011
We give a general theoretical description of electro-osmotic flow at striped superhydrophobic surfaces in a thin double layer limit, and derive a relation between the electro-osmotic mobility and hydrodynamic slip-length tensors. Our analysis demonstrates that electro-osmotic flow shows a very rich behavior controlled by slip length and charge at the gas sectors. In the case of an uncharged liquid-gas interface, the flow is the same or inhibited relative to the flow in a homogeneous channel with a zero interfacial slip. By contrast, it can be amplified by several orders of magnitude provided slip regions are uniformly charged. When gas and solid regions are oppositely charged, we predict a flow reversal, which suggests the possibility of a huge electro-osmotic slip even for electroneutral surfaces. On the basis of these observations we suggest strategies for practical microfluidic devices. © 2011 American Physical Society.
Gokhshtein A.Y.,RAS Frumkin Institute of Physical Chemistry and Electrochemistry
Journal of Solid State Electrochemistry | Year: 2012
Contrary to some recent publications, the trivial definition of the surface charge density q0Q/A does not give any information about the charge Q and area A. Therefore this definition cannot be used as a "simple check," rejecting results of electrochemical experiments where the values Q and A are the independent variables. Experimental confirmation and practical applications can be the two selfcontained checks for the equations of solid-state electrocapillarity. Along with thermodynamics, the kinetic aspect is important here since the charge and area can oscillate in the large frequency range. Cycling the surface charge gives the three different contributions to the alternating surface tension of solids, corresponding to the double layer charging, reversible chemisorption, and discrete transitions closed within the rigid surface layer. The derivative of the charge density with respect to elastic deformation represents chemisorption and can be decreased to negligibly small value at the point of zero charge by increasing the frequency. On the base of the solid-state electrocapillarity, the dependence between the adsorption energy and elastic deformation was measured for the first time. It was thus found that stretching reinforces the bonding of hydrogen to the platinum surface. Acting inside the rigid surface monolayer, the alternating surface tension of solids is an independent tool in solving some complex problems of electrochemistry and solid-state physics. Two consecutive transitions are discovered on platinum instead of two coexistent hydrogen states which earlier were associated with two waves of the charging current. There are three consecutive hydrogen states separated along the potential axis by transitions from one state to another. Similar surface transitions are observed also on iridium, rhodium, and palladium. The number of transitions coincides with the number of finite radial nodes of the wave functions formed by d-electrons of these metals. © Springer-Verlag 2012.
Kulova T.L.,RAS Frumkin Institute of Physical Chemistry and Electrochemistry
Russian Journal of Electrochemistry | Year: 2013
The main principles of operation of modern lithium-ion batteries and the modern trends in development of new-generation batteries are described. © 2013 Pleiades Publishing, Ltd.
Boinovich L.,RAS Frumkin Institute of Physical Chemistry and Electrochemistry
Current Opinion in Colloid and Interface Science | Year: 2010
Further progress has taken place in the theory of surface forces beyond the conventional DLVO theory. The major recent advances are related to more accurate accounting for the ionic nature of liquid interlayer in the calculations of van der Waals forces and for the impact of dispersion interaction of ions with other ions or confining phases on the peculiarities of ion-electrostatic interactions in liquid films. © 2010 Elsevier Ltd.
Roldughin V.I.,RAS Frumkin Institute of Physical Chemistry and Electrochemistry
Colloid Journal | Year: 2013
Gas flow has been considered in a porous membrane with nanosized channels, for which the influence of surface forces and relevant effects must be taken into account. The problem of entropy production in such systems has been discussed. It has been shown that, when calculating the total entropy production in such a system, it is necessary to take into account the entropy production at the inlets and outlets of the channels of the porous body. The entropy production has been determined, and the phenomenological equations describing the heat and mass transfer through the porous body-gas interface have been found. © 2013 Pleiades Publishing, Ltd.
Boinovich L.,RAS Frumkin Institute of Physical Chemistry and Electrochemistry |
Emelyanenko A.,RAS Frumkin Institute of Physical Chemistry and Electrochemistry
Advances in Colloid and Interface Science | Year: 2012
In most fields of technological application of superhydrophobic materials, such as protection against corrosion, icing, and capillary condensation, or micro fluidics applications, a superhydrophobic surface has to operate in contact with aggressive aqueous media. Therefore, the peculiarities of behaviour of hydrophobic and superhydrophobic surfaces on prolonged contact with water and the mechanisms of possible degradation of superhydrophobicity need to be discussed. In this study, a consideration of the physicochemical processes accompanying the contact of hydrophobic and superhydrophobic materials with water, acid, alkaline and saline aqueous solutions is presented on the basis of experimental data on three-phase equilibrium obtained by the sessile drop method. It is shown that simultaneous analysis of the contact angle and contact diameter of the sessile drop and liquid/vapour surface tension allows one to attribute degradation of the superhydrophobic and hydrophobic state to reversible and irreversible processes such as hydrolysis of hydrophobic molecules, growth of an oxide layer and so on. A method for estimating both the portion of wetted area and the intrinsic wettability state (hydrophobic versus hydrophilic) of texture elements for a heterogeneous wetting regime is proposed and discussed. © 2012 Elsevier B.V.
Malkin A.I.,RAS Frumkin Institute of Physical Chemistry and Electrochemistry
Colloid Journal | Year: 2012
The fundamental regularities and contemporary concepts of the nature of Rehbinder's effect, i.e., adsorption-induced reduction of strength, are reviewed. Experimental data on the effect of adsorption-active environment on the fracture of solids, the strength of which is controlled by different interatomic bonds, are generalized. The reasons for the chemical selectivity and the influence of solid supramolecular structures and test conditions on the character of the effect are discussed. © Pleiades Publishing, Ltd., 2012.
Larin A.V.,RAS Frumkin Institute of Physical Chemistry and Electrochemistry
Colloid Journal | Year: 2012
An exact solution obtained for the direct problem concerning the elution dynamics of adsorption in terms of the model of an equilibrium adsorption layer using the gamma function is analyzed. Analytical expressions derived for the functions of moments comprise adsorbent layer lengths, mobile phase velocities, and adsorption constants. The functions are found to be interrelated via the slope coefficients of linear equa- tions. The correctness of the results obtained is confirmed by good agreement between the theory and exper- imental data presented as tabulated values of the moments measured previously for the elution dynamics of Freon 13B1 adsorption on active carbon layers of different lengths. © Pleiades Publishing, Ltd., 2012.