Publications (229)580.52 Total impact
 [Show abstract] [Hide abstract] ABSTRACT: We carried out Monte Carlo simulations of the twopatch colloids in twodimensions. Similar model investigated theoretically in threedimensions exhibited a reentrant phase transition. Our simulations indicate that no reentrant transition exists and the phase diagram for the system is of a swanneck type and corresponds solely to the fluidsolid transition.

Article: Mixtures of ions and amphiphilic molecules in slitlike pores: A density functional approach
[Show abstract] [Hide abstract] ABSTRACT: We investigate microscopic structure and thermodynamic properties of a mixture that contains amphiphilic molecules and charged hard spheres confined in slitlike pores with uncharged hard walls. The model and the density functional approach are the same as described in details in our previous work [Pizio et al., J. Chem. Phys. 140, 174706 (2014)]. Our principal focus is in exploring the effects brought by the presence of ions on the structure of confined amphiphilic particles. We have found that for some cases of anisotropic interactions, the change of the structure of confined fluids occurs via the firstorder transitions. Moreover, if anions and cations are attracted by different hemispheres of amphiphiles, a charge at the walls appears at the zero value of the wall electrostatic potential. For a given thermodynamic state, this charge is an oscillating function of the pore width.  [Show abstract] [Hide abstract] ABSTRACT: Using Monte Carlo simulation method in the canonical ensemble, we have studied the commensurateincommensurate transition in twodimensional finite mixed clusters of Ar and Kr adsorbed on graphite basal plane at low temperatures. It has been demonstrated that the transition occurs when the argon concentration exceeds the value needed to cover the peripheries of the cluster. The incommensurate phase exhibits a similar domainwall structure as observed in pure krypton films at the densities exceeding the density of a perfect $(\sqrt{3}\times\sqrt{3})R30^\circ$ commensurate phase, but the size of commensurate domains does not change much with the cluster size. When the argon concentration increases, the composition of domain walls changes while the commensurate domains are made of pure krypton. We have constructed a simple onedimensional FrenkelKontorovalike model that yields the results being in a good qualitative agreement with the Monte Carlo results obtained for twodimensional systems.
 [Show abstract] [Hide abstract] ABSTRACT: We investigate the electric double layer formed between charged walls of a slitlike pore and a solvent primitive model (SPM) for electrolyte solution. The recently developed version of the weighted density functional approach for electrostatic interparticle interaction is applied to the study of the density profiles, adsorption and selectivity of adsorption of ions and solvent species. Our principal focus, however, is in the dependence of differential capacitance on the applied voltage, on the electrode and on the pore width. We discuss the properties of the model with respect to the behavior of a primitive model, i.e., in the absence of a hardsphere solvent. We observed that the differential capacitance of the SPM on the applied electrostatic potential has the camellike shape unless the ion fraction is high. Moreover, it is documented that the dependence of differential capacitance of the SPM on the pore width is oscillatory, which is in close similarity to the primitive model.
 [Show abstract] [Hide abstract] ABSTRACT: We present a version of density functional approach for the system of patchy colloidal particles confined in slitlike pores with hard walls. Each particle possesses two offcenter sites of the type A and B and in addition to single AA and BB bonds formation of the double ABA and BAB bonds is allowed. The proposed approach is based on the fundamental measure theory and the second order perturbation theory of Wertheim. For the model in question a reentrant phase behavior in bulk system has been found [Kalyuzhnyi Y.V.; Cummings, P.T., J. Chem. Phys. 2013, 139, 104905] . Our calculations revealed that the reentrant phase diagrams are also observed in confined systems. The upper critical temperature decreases with the pore width, while the lower critical temperature increases very slightly.
 [Show abstract] [Hide abstract] ABSTRACT: Using a simple onedimensional FrenkelKontorowa type model, we have demonstrated that finite commensurate chains may undergo the commensurateincommensurate (CIC) transition when the chain is contaminated by isolated impurities attached to the chain ends. Monte Carlo (MC) simulation has shown that the same phenomenon appears in twodimensional systems with impurities located at the peripheries of finite commensurate clusters.
 [Show abstract] [Hide abstract] ABSTRACT: We use density functional theory to study the influence of fluid adsorption on the structure of grafted chain layer. The chains are modeled as freely jointed spheres. The chain segments and spherical molecules of the fluid interact via the LennardJones potential. The fluid molecules are attracted by the substrate. We calculate the excess adsorption isotherms, the average height of tethered chains, and the force acting on selected segments of the chains. The parameters that were varied include the length of grafted chains, the grafting density, the parameters characterizing fluidchain and fluidsurface interactions, the bulk fluid density, and temperature. We show that depending on the density of the bulk fluid the height of the bonded layer increases, remains constant, or decreases with increasing temperature.
 [Show abstract] [Hide abstract] ABSTRACT: We investigate microscopic structure, adsorption, and electric properties of a mixture that consists of amphiphilic molecules and charged hard spheres in contact with uncharged or charged solid surfaces. The amphiphilic molecules are modeled as spheres composed of attractive and repulsive parts. The electrolyte component of the mixture is considered in the framework of the restricted primitive model (RPM). The system is studied using a density functional theory that combines fundamental measure theory for hard sphere mixtures, weighted density approach for inhomogeneous charged hard spheres, and a meanfield approximation to describe anisotropic interactions. Our principal focus is in exploring the effects brought by the presence of ions on the distribution of amphiphilic particles at the wall, as well as the effects of amphiphilic molecules on the electric double layer formed at solid surface. In particular, we have found that under certain thermodynamic conditions a longrange translational and orientational order can develop. The presence of amphiphiles produces changes of the shape of the differential capacitance from symmetric or nonsymmetric belllike to camellike. Moreover, for some systems the value of the potential of the zero charge is nonzero, in contrast to the RPM at a charged surface.
 [Show abstract] [Hide abstract] ABSTRACT: We use density functional theory to investigate adsorption on the solid surfaces modified with endgrafted chains with embedded attractive groups. The chains are modelled as freely joined spheres. They consist of segments A and a short block of segments B that mimics the functional group. The fluid molecules are spherical. All species interact via the LennardJones (126) potential. The substrate is inert with respect to the chain segments and free molecules. We investigate the impact of the position of the Bblock on adsorption of pure fluids, adsorption from binary solutions, the selectivity of the adsorption systems as well as on the structure of the bonded phase.
 [Show abstract] [Hide abstract] ABSTRACT: Many objects of nanoscopic dimensions involve fluidtethered chain interfaces. These systems are of interest for basic science and for several applications, in particular for design of nanodevices for specific purposes. We review recent developments of theoretical methods in this area of research and in particular of density functional (DF) approaches, which provide important insights into microscopic properties of such interfaces. The theories permit to describe the dependence of adsorption, wettability, solvation forces and electric interfacial phenomena on thermodynamic states and on characteristics of tethered chains. Computer simulations for the problems in question are overviewed as well. Theoretical results are discussed in relation to simulation results and to some experimental observations.
 [Show abstract] [Hide abstract] ABSTRACT: We apply a density functional theory to calculate the solvation force in the system involving Janus particles confined between two planar walls. Janus particles are modeled as spheres composed of attractive and repulsive parts and their orientation is described by the vectors representing internal degrees of freedom. We consider the cases of pores with identical walls, as well as the pores with competing walls (the socalled Januslike pores). The density functional approach we employ combines fundamental measure theory with a meanfield approximation for the anisotropic interparticle interaction. We study how the solvation force and the orientational structure of confined particles depend on the competition between the surface field and the interactions between confined molecules and on the parameters of the model such as temperature and density. It is shown that the anisotropic interaction between the confined molecules and the character of the walls significantly influence the solvation force.
 [Show abstract] [Hide abstract] ABSTRACT: The structure of grafted chain layers immersed in an explicit solvent consisting of chain molecules is studied using density functional theory. We consider bonded layers built of short grafted chains at a moderate grafting density. We investigate the grafted layers in contact with oligomeric solvents and oligomermonomer solutions. The chain molecules are freely jointed spherical segments. The substrate is assumed to be inert with respect to the grafted chains. The mobile molecules interact with the surface via LennardJones (93) potential. The interactions between mobile chains, monomers, as well as segments of the tethered chains, are described by LennardJones (126) potential. We discuss how the structure of the grafted chain layer depends on the length of mobile chains and strengths of grafted chainoligomer, oligomersubstrate, oligomeroligomer and oligomermonomer interactions. We study the impact of mixture composition on the height of the bonded layer for selected model systems. The results are consistent with previous experimental and simulation data.
 [Show abstract] [Hide abstract] ABSTRACT: We propose application of density functional theory to calculate the force acting on a selected segment of a tethered polymer chain that leads to stretching the chain. The density functional allows one to determine the effects due to the presence of other chains and solvent molecules. For high and moderate solvent densities the plot of the force versus the distance of the segment from the surface exhibits oscillatory behavior that has not been predicted by other approaches. (C) 2013 AIP Publishing LLC.
 [Show abstract] [Hide abstract] ABSTRACT: We apply a density functional theory to describe properties of a restricted primitive model of an ionic fluid in slitlike pores. The pore walls are modified by grafted chains. The chains are built of uncharged or charged segments. We study the influence of modification of the pore walls on the structure, adsorption, ion selectivity, and the electric double layer capacitance of ionic fluid under confinement. The brush built of uncharged segments acts as a collection of obstacles in the walls vicinity. Consequently, separation of charges requires higher voltages, in comparison to the models without brushes. At high grafting densities the formation of crowdingtype structure is inhibited. The double layer structure becomes more complex in various aspects, if the brushes are built of charged segments. In particular, the evolution of the brush height with the bulk fluid density and with the charge on the walls depends on the length of the blocks of charged spheres as well as on the distribution of charged species along chains. We also investigated how the dependence of the double layer capacitance on the electrostatic potential (or on the charge on the walls) changes with grafting density, the chain length, distribution of charges along the chain, the bulk fluid density, and, finally, with the pore width. The shape of the electric double layer capacitance vs. voltage changes from a camellike to belllike shape, if the bulk fluid density changes from low to moderate and high. If the bulk density is appropriately chosen, it is possible to alter the shape of this curve from the double hump to single hump by changing the grafting density. Moreover, in narrow pores one can observe the capacitance curve with even three humps for a certain set of parameters describing brush. This behavior illustrates how strong the influence of brushes on the electric double layer properties can be, particularly for ionic fluids in narrow pores.
 [Show abstract] [Hide abstract] ABSTRACT: We investigate the structure and adsorption of amphiphilic molecules at planar walls modified by tethered chain molecules using density functional theory. The molecules are modeled as spheres composed of a hydrophilic and hydrophobic part. The pinned chains are treated as tangentially jointed spheres that can interact with fluid molecules via orientationdependent forces. Our density functional approach involves fundamental measure theory, thermodynamic perturbation theory for chains and a meanfield approximation for describing the anisotropic interactions. We study the adsorption of the particles, focusing on the competition between the external field (due to the surface and due to attached chain molecules) and the interactioninduced ordering phenomena.
 [Show abstract] [Hide abstract] ABSTRACT: We apply recently developed version of a density functional theory [Z. Wang, L. Liu, and I. Neretnieks, J. Phys.: Condens. Matter 23, 175002 (2011)] to study adsorption of a restricted primitive model for an ionic fluid in slitlike pores in the absence of interactions induced by electrostatic images. At present this approach is one of the most accurate theories for such model electric double layers. The dependencies of the differential double layer capacitance on the pore width, on the electrostatic potential at the wall, bulk fluid density, and temperature are obtained. We show that the differential capacitance can oscillate as a function of the pore width dependent on the values of the above parameters. The number of oscillations and their magnitude decrease for high values of the electrostatic potential. For very narrow pores, close to the ion diameter, the differential capacitance tends to a minimum. The dependence of differential capacitance on temperature exhibits maximum at different values of bulk fluid density and applied electrostatic potential.
 [Show abstract] [Hide abstract] ABSTRACT: We use a version of the density functional theory to study the solvation force between two plates modified with a tethered layer of chains. The chains are built of tangentially jointed charged spherical segments. The plates are immersed in an electrolyte solution that involves cations, anions and solvent molecules. The latter molecules are modelled as hard spheres. We study the dependence of the solvation force and the structure of chains and of solute molecules on the grafting density, length of chains, architecture of the chains and on concentration of the solute.

Article: Adsorption from OligomerMonomer Solutions on the Surfaces Modified with EndGrafted Chains
[Show abstract] [Hide abstract] ABSTRACT: A density functional theory has been applied to study adsorption from oligomermonomer solutions on solid surfaces modified with endgrafted polymers. Chains are modeled as freely jointed tangent spheres. All spherical species interact via LennardJones (126) potential. The grafted chains are not attracted by the surface. Fluid molecules interact with the substrate via LennardJones (93) potential. It is shown how a shape of the relative excess adsorption isotherms depends on such parameters as the oligomer length, the grafting density, oligomersubstrate interactions, oligomergrafted chains interactions, and oligomermonomer interactions in the bulk solution. As attractive interactions between free and grafted chains strengthen, the relative excess adsorption isotherm can change from negative, through Sshaped with an adsorption azeotropic point, to positive in the whole concentration region. A change of oligomermonomer interactions causes the opposite effects. For low grafting densities of attractive bonds, the relative excess of oligomers increases, reaches a maximum, and decreases. The structure of surface layers is also analyzed.  [Show abstract] [Hide abstract] ABSTRACT: We apply density functional theory to study adsorption of ions, treated in the framework of the restricted primitive model (RPM), on surfaces modified by tethered polyampholytes. The residual electrostatic contribution to the free energy functional is approximated by using the approach proposed by Wang et al. [J. Phys.: Condens. Matter 23, 175002 (2011)] for simple nonuniform RPMs systems. Our research concentrates on the problems how the distribution of the charges within chains of polyampholytes changes the selectivity of adsorption of ions species, the structure of the surface layer, and its electric properties.
 [Show abstract] [Hide abstract] ABSTRACT: A recently proposed local second contact value theorem [Henderson D., Boda D., J. Electroanal. Chem., 2005, 582, 16] for the charge profile of an electric double layer is used in conjunction with the existing Monte Carlo data from the literature to assess the contact behavior of the electrodeion distributions predicted by the density functional theory. The results for the contact values of the co and counterion distributions and their product are obtained for the symmetric valency, restricted primitive model planar double layer for a range of electrolyte concentrations and temperatures. Overall, the theoretical results satisfy the second contact value theorem reasonably well, the agreement with the simulations being semiquantitative or better. The product of the co and counterion contact values as a function of the electrode surface charge density is qualitative with the simulations with increasing deviations at higher concentrations.
Publication Stats
2k  Citations  
580.52  Total Impact Points  
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Institutions

19772015

Maria CurieSklodowska University in Lublin
 • Department for The Modelling of Physicochemical Processes
 • Faculty of Chemistry
 • Department of Theoretical Chemistry
 • Institute of Biology and Biochemistry
Lyublin, Lublin Voivodeship, Poland


19951996

Metropolitan Autonomous University
 Departamento de Física
Ciudad de México, The Federal District, Mexico


1982

Maria SkłodowskaCurie Institute of Oncology
Cracovia, Lesser Poland Voivodeship, Poland
