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  • 1.
    Arkhipov, Victor P.
    et al.
    Kazan National Research Technological University.
    Idiyatullin, Zhamil Sh
    Kazan National Research Technological University.
    Potapova, Elisaveta
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Antzutkin, Oleg
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Filippov, Andrei
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Micelles and aggregates of oxyethylated isononylphenols and their extraction properties near cloud point2014Ingår i: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 118, nr 20, s. 5480-5487Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We used nuclear magnetic resonance (NMR) spectroscopy and dynamic light scattering (DLS) techniques to study the structural and dynamic properties of micellar solutions of nonionic surfactants of a homologous series of oxyethylated isononylphenols - C9H19C6H 4O(C2H4O)nH, where n = 6, 8, 9, 10, or 12 - in a wide range of temperatures, including cloud points. The radii of the micelles and aggregates, as well as their compositions at different concentrations of surfactant, were determined. Using aqueous phenol solutions as a model, we studied the process of cloud point extraction with oxyethylated isononylphenols

  • 2.
    Bjorklund, Robert B.
    et al.
    Linköping University.
    Hedlund, Jonas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Sterte, Johan
    Arwin, Hans
    Linköping University.
    Vapor adsorption in thin silicalite-1 films studied by spectroscopic ellipsometry1998Ingår i: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 102, nr 12, s. 2245-2250Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Thin films of silicalite-1 grown on silicon substrates were studied by spectroscopic ellipsometry. Analysis of spectra using an optical model consisting of a single porous layer on silicon yielded average film thicknesses of 84 and 223 nm for films synthesized for 10 and 30 h. Void fraction for the films was 0.32-0.33. Vapor adsorption from a nitrogen carrier gas at room temperature was monitored by ellipsometry. Isotherms for different adsorbates were obtained by analysis of spectra taken at different vapor concentrations using an optical model where the void volume was filled with both nitrogen and condensed vapors. Quantification of the condensed vapor amount was based on the changes in refractive index when adsorbates replaced nitrogen in the pores. Adsorbate volumes for water, toluene, 1-propanol, and hexane were 0.12, 0.12, 0.15, and 0.17 cm3 liquid g-1 film, respectively.

  • 3.
    Chernyshova, Irina V.
    et al.
    St. Petersburg State Technical University.
    Rao, K. Hanumantha
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    A new approach to the IR spectroscopic study of molecular orientation and packing in adsorbed monolayers: orientation and packing of long-chain primary amines and alcohols on quartz2001Ingår i: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 105, nr 4, s. 810-820Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A new method is suggested for determining the molecular orientation in adsorbed films with uniaxial and biaxial anisotropy from two (s- and p-polarized) IRRAS spectra of the same sample, measured at the optimal angle of incidence. The method is simple, does not use the film thickness, and is internally stable with respect to the uncertainty in the input optical parameters of the anisotropic film. The advantages and limitations of the method are discussed. To validate the method, we determined the orientation of hexadecylamine and hexadecyl alcohol adsorbed on a quartz surface. It is shown that at a concentration above the concentration of 2D precipitation but below the concentration of 3D precipitation, hydrocarbon chains in the adsorbed amine monolayer are well-packed in a monoclinic (biaxial) subcell with a tilt angle of about 30°. Chaotically arranged crystallites of the amine molecules appear at the surface at a concentration higher than the concentration of 3D precipitation. Adsorbed monolayers of the alcohol turn out to have a hexagonal structure, in which the hydrocarbon tails are "flip-flop" positioned and tilted by 25-30° from the surface normal.

  • 4.
    Gannon, Greg
    et al.
    Tyndall National Institute, University College Cork.
    Larsson, Andreas
    Greer, James C.
    Tyndall National Institute, University College Cork.
    Thompson, Damien J.
    Tyndall National Institute, University College Cork.
    Guanidinium chloride molecular diffusion in aqueous and mixed water-ethanol solutions2008Ingår i: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 112, nr 30, s. 8906-8911Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Solutions containing guanidinium chloride (GdmCl), or equivalently guanidine hydrochloride (GdnHCl), are commonly used to denature macromolecules such as proteins and DNA in, for example, microfluidics studies of protein unfolding. To design and study such applications, it is necessary to know the diffusion coefficients for GdmCl in the solution. To this end, we use molecular dynamics simulations to calculate the diffusion coefficients of GdmCl in water and in water-ethanol solutions, for which no direct experimental measurements exist. The fully atomistic simulations show that the guandinium cation Gdm + diffusion decreases as the concentration of both Gdm + and ethanol in the solution increases. The simulations are validated against available literature data, both transformed measured viscosity values and computed diffusion coefficients, and we show that a prudent choice of water model, namely TIP4P-Ew, gives calculated diffusion coefficients in good agreement with the transformed measured viscosity values. The calculated Gdm + diffusion behavior is explained as a dynamic mixture of free cation, stacked cation, and ion-paired species in solution, with weighted contributions to Gdm + diffusion from the stacked and paired states helping explain measured viscosity data in terms of atom-scale dynamics

  • 5.
    Gannon, Greg
    et al.
    Theory Modelling and Design Centre, Tyndall National Institute, University College Cork.
    O'Dwyer, Colm
    Department of Physics and Energy, Materials and Surface Science Institute, University of Limerick.
    Larsson, Andreas
    Thompson, Damien J.
    Theory Modelling and Design Centre, Tyndall National Institute, University College Cork.
    Interdigitating organic bilayers direct the short interlayer spacing in hybrid organic-inorganic layered vanadium oxide nanostructures2011Ingår i: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 115, nr 49, s. 14518-14525Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Layered metal oxides provide a single-step route to sheathed superlattices of atomic layers of a variety of inorganic materials, where the interlayer spacing and overall layered structure forms the most critical feature in the nanomaterials' growth and application in electronics, health, and energy storage. We use a combination of computer simulations and experiments to describe the atomic-scale structure, dynamics and energetics of alkanethiol-intercalated layered vanadium oxide-based nanostructures. Molecular dynamics (MD) simulations identify the unusual substrate-constrained packing of the alkanethiol surfactant chains along each V 2O 5 (010) face that combines with extensive interdigitation between chains on opposing faces to maximize three-dimensional packing in the interlayer regions. The findings are supported by high resolution electron microscopy analyses of synthesized alkanethiol-intercalated vanadium oxide nanostructures, and the preference for this new interdigitated model is clarified using a large set of MD simulations. This dependency stresses the importance of organic-inorganic interactions in layered material systems, the control of which is central to technological applications of flexible hybrid nanomaterials

  • 6. Ji, Xiaoyan
    et al.
    Tan, Sugata P.
    University of Wyoming.
    Adidharma, Hertanto
    University of Wyoming.
    Radosz, Maciej
    University of Wyoming.
    Statistical associating fluid theory coupled with restrictive primitive model extended to bivalent ions: SAFT2: 2. Brine/seawater properties predicted2006Ingår i: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 110, s. 16700-16706Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Statistical associating fluid theory coupled with restricted primitive model (SAFT2) represents the properties of aqueous multiple-salt solutions, such as brine/seawater. The osmotic coefficients, densities, and vapor pressures are predicted without any additional parameters using the salt hydrated diameters obtained for single-salt solutions. For a given ion composition of brine, the predicted vapor pressure, osmotic coefficient, activity of water, and density are found to agree with the experimental data.

  • 7. Kundu, Tarun
    et al.
    Rao, Hanumantha
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Parker, S.C.
    School of Chemistry, University of Bath.
    Competitive adsorption on wollastonite: an atomistic simulation approach2005Ingår i: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 109, nr 22, s. 11286-11295Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Atomistic simulation techniques are used to simulate surface structure and adsorption behavior of scarcely floatable wollastonite mineral in the presence of molecular and dissociated water, methanoic acid, and methylamine. The latter two additives represent the two widely used collector head-group molecules. The static energy minimization code METADISE was used to perform the simulation to obtain pure surface energy and adsorption energy in the presence of added molecule. The hydroxylation was performed on those surfaces where low-coordinated silicon was made to saturate by bonding with hydroxyl group, and the subsequent charge neutralization was maintained by adding proton on single-coordinated surface oxygen. A comparison of surface energies revealed that all the surfaces become stabilized in the presence of added molecules; however, the presence of methylamine decreased the surface energy to lower values. Adsorption of dissociated water is preferred by the {100} and {102} surfaces, whereas the {001} surface preferred methylamine adsorption, because these show highly negative adsorption energies. In terms of molecular adsorption, the preferred adsorption sequence for all the surfaces is methylamine > methanoic acid > water without considering coadsorption. For the {100} and {102} surfaces, the adsorption energy values of carboxylic acid and amine are more negative than that of water and therefore we conclude that both carboxyl and amine head-group molecules adsorb preferably on wollastonite. Our simulation verify usability of carboxylic acid head group as widely used collectors for wollastonite flotation and, at the same time, it predicts the use of amine head-group collectors as possible modifiers, which corresponds well with our experimental findings.

  • 8. Larsson, Andreas
    et al.
    Nolan, Michael
    NMRC, University College, Lee Maltings, Cork.
    Greer, James C.
    NMRC, University College, Lee Maltings, Cork.
    Interactions between thiol molecular linkers and the Au13 nanoparticle2002Ingår i: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, s. 5931-5937Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The structure and binding of thiol molecular linkers to gold surfaces and nanoparticles is central to the understanding of the electronic properties of self-assembled monolayers and, of relevance to recent studies, to nanoscale assemblages consisting of molecular wires and metal nanoparticles. The study of mono-molecular electron transport generally requires consideration of bonding with irregular metallic contacts or poorly defined surfaces such as break junctions, electromigration generated gaps, and scanning probe microscopy tips. These structures can locally bear a closer resemblance to atomic clusters, as compared to neat metallic surfaces. It has also emerged that the prediction and understanding of the electronic transport properties for molecular wires and nanoscale assemblies requires detailed knowledge of thiolate-gold cluster interactions. Recent debate has focused on the nature of the thiolate bonding to surfaces, and the effect of disordering and distortion in gold cluster structures on thiolate bonding. We apply density functional theory methods to study the interactions of two thiols-methanethiol and benzenethiol-with Au13, a gold "magic" number cluster. Our study emphasizes the effects of thiolate bonding on the electronic structure of the linker molecule and gold cluster. We find significant local distortion of the gold cluster upon bonding to a thiol group, resulting in modifications to the electronic structure of the complex. Consideration of a finite gold cluster avoids many of the issues related to thiolate bonding on gold surfaces, and allows us to assess the impact of bonding to gold nanoparticles in terms of electronic structure. We discuss our findings in relation to electron transport properties in self-assembled systems.

  • 9. Lebedkin, S.
    et al.
    Hull, W.E.
    Soldatov, Alexander
    Renker, B.
    Kappes, M. M.
    Structure and properties of the fullerene dimer C140 produced by pressure treatment of C702000Ingår i: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 104, nr 17, s. 4101-4110Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A [2+2] cycloaddition cap-to-cap C70 dimer with C2h molecular symmetry was synthesized in high yield by pressure treatment of polycrystalline C70 at 1 GPa and 200° C. It was separated from unreacted monomers by chromatography and characterized by 13C NMR, Raman, and infrared spectroscopy, and other methods. Remarkably, only one isomer was produced out of the five possible [2+2] cycloaddition products which have equally low formation energies according to semiempirical modeling calculations. The dimer obtained is the one favored when C70 molecules adopt an ordered packing with parallel D5 axes. The intercage bonding in C140, its thermal stability, and intercage vibrational modes are similar to those found for the C60 dimer, C120. Both dimers photodissociate to the monomers in solution, probably via excited triplet states. The UV absorption and fluorescence properties of C140 are not very different from those of C70, suggesting only weak electronic interactions between the two cages of C140. In comparison, the pressure-induced dimerization of C60, under the conditions used for C70, results mainly in C60 oligomers and polymeric chains, but the dimer C120 could be isolated at low yield when short reaction times (≤5 min) were used.

  • 10.
    Malysheva, Lyuba
    et al.
    Bogolyubov Institute for Theoretical Physics, Kiev.
    Onipko, Alexander
    Valiokas, Ramunas
    Linköping University, Division of Molecular Physics, Department of Physics and Measurement Technology.
    Liedberg, Bo
    Linköping University, Division of Molecular Physics, Department of Physics and Measurement Technology.
    First-principle DFT and MP2 modeling of infrared reflection-absorption spectra of oriented helical ethylene glycol oligomers2005Ingår i: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 109, nr 27, s. 13221-7Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    First-principle modeling is used to obtain a comprehensive understanding of infrared reflection absorption (RA) spectra of helical oligo(ethylene glycol) (OEG) containing self-assembled monolayers (SAMs). Highly ordered SAMs of methyl-terminated 1-thiaoligo(ethylene glycols) [HS(CH2CH2O)(n)CH3, n = 5, 6] on gold recently became accessible for systematic infrared analyses [Vanderah et al., Langmuir, 2003, 19, 3752]. We utilized the quoted experimental data to validate the first-principle modeling of infrared RA spectra of HS(CH2CH2O)(5,6)CH3 obtained by (i) DFT methods with gradient corrections (using different basis sets, including 6-311++G) and (ii) HF method followed by a Moller-Plesset (MP2) correlation energy correction. In focus are fundamental modes in the fingerprint and CH-stretching regions. The frequencies and relative intensities in the calculated spectra for a single molecule are unambiguously identified with the bands observed in the experimental RA spectra of the corresponding SAMs. In addition to confirming our earlier assignment of the dominating peak in the CH-stretching region to CH2 asymmetric stretching vibrations, all other spectral features observed in that region have received an interpretation consistent (but not in all cases coinciding) with previous investigations. The obtained results provide an improved understanding of the orientation and conformation of the molecular building blocks within OEG-containing assemblies, which, in our opinion, is crucial for being able to predict the folding and phase characteristics and interaction of OEG-SAMs with water and proteins

  • 11.
    Mu, Liwen
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement. Intelligent Composites Laboratory, Department of Chemical and Biomolecular Engineering, The University of Akron.
    Shi, Yijun
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Hua, Jing
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Zhuang, Wei
    College of Biotechnology and Pharmaceutical Engineering, National Engineering Technique Research Center for Biotechnology, Nanjing Tech University.
    Zhu, Jiahua
    Intelligent Composites Laboratory, Department of Chemical and Biomolecular Engineering, The University of Akron.
    Engineering Hydrogen Bonding Interaction and Charge Separation in Bio-polymers for Green Lubrication2017Ingår i: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 121, nr 22, s. 5669-5678Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Synthetic additives are widely used in lubricants nowadays to upgrade lubrication properties. The potential of integrating sustainable components in modern lubricants has rarely been studied yet. In this work, two sustainable resources lignin and gelatin have been synergistically incorporated into ethylene glycol (EG), and their tribological properties were systematically investigated. The abundant hydrogen bonding sites in lignin and gelatin as well as their interchain interaction via hydrogen bonding play the dominating roles in tuning the physicochemical properties of the mixture and improving lubricating properties. Moreover, the synergistic combination of lignin and gelatin induces charge separation of gelatin that enables its preferable adsorption on the friction surface through electrostatic force and forms a robust lubrication layer. This layer will be strengthened by lignin through the interpolymer chain hydrogen bonding. At an optimized lignin:gelatin mass ratio of 1:1 and 19 wt % loading of each in EG, the friction coefficient can be greatly stabilized and the wear loss was reduced by 89% compared to pure EG. This work presents a unique synergistic phenomenon between gelatin and lignin, where hydrogen bonding and change separation are revealed as the key factor that bridges the individual components and improves overall lubricating properties.

  • 12.
    Ravishankar, Raman
    et al.
    Centrum Oppervlaktechemie en Katalyse.
    Kirschhock, Christine
    Centrum Oppervlaktechemie en Katalyse.
    Knops-Gerrits, Peter-Paul
    Centrum Oppervlaktechemie en Katalyse.
    Feijen, Eddy J.P.
    Centrum Oppervlaktechemie en Katalyse.
    Grobet, Piet J.
    Centrum Oppervlaktechemie en Katalyse.
    Vanoppen, Peter
    Laboratorium Moleculaire Dynamica en Spectroscopie.
    Schryver, Frans C. De
    Laboratorium Moleculaire Dynamica en Spectroscopie.
    Miele, Gerhard
    Department of Materials Science, Division of Structural Research, University of Technology, Darmstadt.
    Fuess, Harmut
    Department of Materials Science, Division of Structural Research, University of Technology, Darmstadt.
    Shoeman, Brian J.
    Luleå tekniska universitet.
    Jacobs, Pierre A.
    Centrum Oppervlaktechemie en Katalyse.
    Martens, Johan A.
    Centrum Oppervlaktechemie en Katalyse.
    Characterization of Nanosized Material Extracted from Clear Suspensions for MFI Zeolite Synthesis1999Ingår i: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 103, nr 24, s. 4960-4964Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The silica species contained in an aged clear suspension, which upon heating gives rise to the crystallization of Silicalite-1, were extracted with 80% efficiency using a sequence of acidification, salting out, phase transfer into organic solvent, and freeze-drying methods. This silica powder was characterized by X-ray scattering, transmission electron microscopy, atomic force microscopy, and 29Si magic angle spinning nuclear magnetic resonance. These techniques gave evidence for the presence of a very specific morphology, corresponding to slab shaped particles, with dimensions of 1.3 × 4.0 × 4.0 nm. The nanoslabs have the MFI structure with nine channel intersections per particle, each containing a TPA cation. The identity of the extracted nanoslabs with the species in suspension is evidenced with in situ and ex situ X-ray scattering.

  • 13.
    Ravishankar, Raman
    et al.
    Centrum Oppervlaktechemie en Katalyse.
    Kirschhock, Christine
    Centrum Oppervlaktechemie en Katalyse.
    Shoeman, Brian J.
    Luleå tekniska universitet.
    Vanoppen, Peter
    Laboratorium Moleculaire Dynamica en Spectroscopie.
    Grobet, Piet J.
    Centrum Oppervlaktechemie en Katalyse.
    Storck, Sebastian
    Max-Planck-Institut für Kohlenforschung.
    Maier, William F.
    Max-Planck-Institut für Kohlenforschung.
    Martens, Johan A.
    Centrum Oppervlaktechemie en Katalyse.
    Schryver, Frans C. De
    Laboratorium Moleculaire Dynamica en Spectroscopie.
    Jacobs, Pierre A.
    Centrum Oppervlaktechemie en Katalyse.
    Physicochemical characterization of silicalite-1 nanophase material1998Ingår i: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 102, nr 15, s. 2633-2639Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A silicalite-1 nanophase material with an elementary particle size of 18-100 nm is synthesized from clear solution and isolated and purified using supercentrifugation. The nanopowder is characterized in detail using scanning electron microscopy, high-resolution transmission electron microscopy, attenuated force microscopy, 29Si magic angle spinning NMR, 13C cross polarization magic angle spinning NMR, X-ray diffraction, dinitrogen physisorption, and thermogravimetric analysis and compared with micrometer-sized silicalite-1. The nanosized and micrometer-sized materials have many common properties including the refined structure and the nature and concentrations of tetrapropylammonium species incorporated during the synthesis. Unique properties of the nanophase are a splitting of the characteristic framework vibration at 550 cm-1 into a doublet at 555 and 570 cm-1, a high concentration of defect sites, and a strain in the crystallites along the "a" crystallographic direction. The nanophase exhibits a two-stage dinitrogen physisorption in the low-pressure region, ascribed to adsorptions in micropores created by the stacking of the nanoparticles in addition to adsorptions in the intracrystalline micropores.

  • 14.
    Tan, Sugata P.
    et al.
    University of Wyoming.
    Ji, Xiaoyan
    Adidharma, Hertanto
    University of Wyoming.
    Radosz, Maciej
    University of Wyoming.
    Statistical associating fluid theory coupled with restrictive primitive model extended to bivalent ions: SAFT2: 1. Single salt + water solutions2006Ingår i: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 110, s. 16694-16699Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Statistical associating fluid theory coupled with the restricted primitive model is extended to multivalent ions by relaxing the range of the square-well width parameter, which leads to a new dispersion term approximation and calls for a new set of salt and ion parameters. This new approximation, referred to as SAFT2, requires a single set of parameters derived from the salt (mean ionic) activity coefficients and liquid densities of single-salt solutions for five cations (Li+, Na+, K+, Ca2+, Mg2+), six anions (Cl-, Br-, I-, NO3-, SO4-2, HCO3-), and 24 salts. These parameters, in turn, are shown to predict the osmotic coefficients for single salt + water solutions.

  • 15.
    Thompson, Damien J.
    et al.
    Tyndall National Institute, University College Cork.
    Larsson, Andreas
    Modeling competitive guest binding to β-cyclodextrin molecular printboards2006Ingår i: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 110, nr 33, s. 16640-16645Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Anchoring of functionalized guest molecules to self-assembled monolayers (SAMs) is key to the development of molecular printboards for nanopatterning. One very promising system involves guest binding to immobilized β-cyclodextrin (β-CD) hosts, with guest:host recognition facilitated by a hydrophobic interaction between uncharged anchor groups on the guest molecule and β-CD hosts self-assembled at gold surfaces. We use molecular dynamics free energy (MDFE) simulations to describe the specificity of guest:β-CD association. We find good agreement with experimental thermodynamic measurements for binding enthalpy differences between three commonly used phenyl guests: benzene, toluene, and t-butylbenzene. van der Waals interaction with the inside of the host cavity accounts for almost all of the net stabilization of the larger phenyl guests in β-CD. Partial and full methylation of the secondary rim of β-CD decreases host rigidity and significantly impairs binding of both phenyl and larger adamantane guest molecules. The β-CD cavity is also very intolerant of guest charging, penalizing the oxidized state of ferrocene by at least 7 kcal/mol. β-CD hence expresses moderate specificity toward uncharged organic guest molecules by van der Waals recognition, with a much higher specificity calculated for electrostatic recognition of organometallic guests.

  • 16.
    Wang, Yonglei
    et al.
    Department of Materials and Environmental Chemistry, Arrhenius Laboratory, Stockholm University.
    Sarman, Sten S.
    Department of Materials and Environmental Chemistry, Arrhenius Laboratory, Stockholm University.
    Glavatskih, Sergei
    System and Component Design, KTH, Royal Institute of Technology , Machine Design, KTH Royal Institute of Technology, SE-10044 Stockholm, Sweden, Department of Physics, Warwick University, Coventry.
    Antzutkin, Oleg
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Rutland, Mark W.
    Surface and Corrosion Science, School of Chemical Science and Engineering, KTH – Royal Institute of Technology, Department of Materials and Environmental Chemistry, Arrhenius Laboratory, Stockholm University.
    Laaksonen, Aatto
    Department of Materials and Environmental Chemistry, Arrhenius Laboratory, Stockholm University.
    Atomistic insight into tetraalkylphosphonium-bis(oxalato)borate ionic liquid/water mixtures: I. Local microscopic structure2015Ingår i: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 119, nr 16, s. 5251-5264Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Atomistic simulations have been performed to investigate the microscopic structural organization of aqueous solutions of trihexyltetradecylphosphonium bis(oxalato)borate ([P6,6,6,14][BOB]) ionic liquid (IL). The evolution of the microscopic liquid structure and the local ionic organization of IL/water mixtures as a function of the water concentration is visualized and systematically analyzed via radial and spatial distribution functions, coordination numbers, hydrogen bond network, and water clustering analysis. The microscopic liquid structure in neat IL is characterized by a connected apolar network composed of the alkyl chains of [P6,6,6,14] cations and isolated polar domains consisting of the central segments of [P6,6,6,14] cations and [BOB] anions, and the corresponding local ionic environment is described by direct contact ion pairs. In IL/water mixtures with lower water mole fractions, the added water molecules are dispersed and embedded in cavities between neighboring ionic species and the local ionic structure is characterized by solvent-shared ion pairs through cation-water-anion triple complexes. With a gradual increase in the water concentration in IL/water mixtures, the added water molecules tend to aggregate and form small clusters, intermediate chain-like structures, large aggregates, and eventually a water network in water concentrated simulation systems. A further progressive dilution of IL/water mixtures leads to the formation of self-organized micelle-like aggregates characterized by a hydrophobic core and hydrophilic shell consisting of the central polar segments in [P6,6,6,14] cations and [BOB] anions in a highly branched water network. The striking structural evolution of the [P6,6,6,14][BOB] IL/water mixtures is rationalized by the competition between favorable hydrogen bonded interactions and strong electrostatic interactions between the polar segments in ionic species and the dispersion interactions between the hydrophobic alkyl chains in [P6,6,6,14] cations

  • 17.
    Wang, Yong-Lei
    et al.
    Department of Materials and Environmental Chemistry, Arrhenius Laboratory, Stockholm University.
    Shah, Faiz Ullah
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Glavatskih, Sergei
    System and Component Design, KTH, Royal Institute of Technology.
    Antzutkin, Oleg
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Laaksonen, Aatto
    Department of Materials and Environmental Chemistry, Arrhenius Laboratory, Stockholm University.
    Atomistic insight into orthoborate-based ionic liquids: force field development and evaluation2014Ingår i: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 118, nr 29, s. 8711-8723Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We have developed an all-atomistic force field for a new class of halogen-free chelated orthoboratephosphonium ionic liquids. The force field is based on an AMBER framework with determination of force field parameters for phosphorus and boron atoms, as well as refinement of several available parameters. The bond and angle force constants were adjusted to fit vibration frequency data derived from both experimental measurements and ab initio calculations. The force field parameters for several dihedral angles were obtained by fitting torsion energy profiles deduced from ab initio calculations. To validate the proposed force field parameters, atomistic simulations were performed for 12 ionic liquids consisting of tetraalkylphosphonium cations and chelated orthoborate anions. The predicted densities for neat ionic liquids and the [P6,6,6,14][BOB] sample, with a water content of approximately 2.3−2.5 wt %, are in excellent agreement with available experimental data. The potential energy components of 12 ionic liquids were discussed in detail. The radial distribution functions and spatial distribution functions were analyzed and visualized to probe the microscopic ionic structures of these ionic liquids. There are mainly four high-probability regions of chelated orthoborate anions distributed around tetraalkylphosphonium cations in the first solvation shell, and such probability distribution functions are strongly influenced by the size of anions.

  • 18.
    Wang, Yonglei
    et al.
    Department of Materials and Environmental Chemistry, Arrhenius Laboratory, Stockholm University.
    Shimpi, Manishkumar
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Sarman, Sten S.
    Department of Materials and Environmental Chemistry, Arrhenius Laboratory, Stockholm University.
    Antzutkin, Oleg
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Glavatskih, Sergei
    System and Component Design, KTH, Royal Institute of Technology , Machine Design, KTH Royal Institute of Technology, SE-10044 Stockholm, Sweden, Department of Physics, Warwick University, Coventry.
    Kloo, Lars
    Applied Physical Chemistry, Department of Chemistry, KTH Royal Institute of Technology.
    Laaksonen, Aatto
    Department of Materials and Environmental Chemistry, Arrhenius Laboratory, Stockholm University.
    Atomistic insight into tetraalkylphosphonium-bis(oxalato)borate ionic liquid/water mixtures: 2. Volumetric and Dynamic Properties2016Ingår i: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 120, nr 30, s. 7446-7455Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Atomistic simulations have been performed to investigate the microscopic structural organization of aqueous solutions of trihexyltetradecylphosphonium bis(oxalato)borate ([P6,6,6,14][BOB]) ionic liquid (IL). The evolution of the microscopic liquid structure and the local ionic organization of IL/water mixtures as a function of the water concentration is visualized and systematically analyzed via radial and spatial distribution functions, coordination numbers, hydrogen bond network, and water clustering analysis. The microscopic liquid structure in neat IL is characterized by a connected apolar network composed of the alkyl chains of [P6,6,6,14] cations and isolated polar domains consisting of the central segments of [P6,6,6,14] cations and [BOB] anions, and the corresponding local ionic environment is described by direct contact ion pairs. In IL/water mixtures with lower water mole fractions, the added water molecules are dispersed and embedded in cavities between neighboring ionic species and the local ionic structure is characterized by solvent-shared ion pairs through cation-water-anion triple complexes. With a gradual increase in the water concentration in IL/water mixtures, the added water molecules tend to aggregate and form small clusters, intermediate chain-like structures, large aggregates, and eventually a water network in water concentrated simulation systems. A further progressive dilution of IL/water mixtures leads to the formation of self-organized micelle-like aggregates characterized by a hydrophobic core and hydrophilic shell consisting of the central polar segments in [P6,6,6,14] cations and [BOB] anions in a highly branched water network. The striking structural evolution of the [P6,6,6,14][BOB] IL/water mixtures is rationalized by the competition between favorable hydrogen bonded interactions and strong electrostatic interactions between the polar segments in ionic species and the dispersion interactions between the hydrophobic alkyl chains in [P6,6,6,14] cations

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