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  • 1.
    Baran, Jakub D.
    et al.
    Tyndall National Institute, University College Cork.
    Larsson, Andreas
    Structure and energetics of shuttlecock-shaped tin-phthalocyanine on Ag(111: A density functional study employing dispersion correction2012Ingår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, s. 9487-9497Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The reversible switch between two electronically and/or geometrically distinct states of a single molecule adsorbed on a well-characterized substrate is of high technological interest due to its possible use as single molecule devices and novel molecular memories. We have studied shuttlecock-shaped metal phthalocyanines, which can adsorb on surfaces in two distinct adsorption configurations, depending on if the central metal atom points toward or away from the surface, and we report on the adsorption of tin-phthalocyanine (SnPc) on an Ag(111) surface using density functional theory (DFT) including a semiempirical dispersion correction (DFT-D).We discuss the binding mechanism in detail and show that the adsorption of SnPc in these two orientations is driven by very different interactions. While "Sn-down" adsorption involves chemical bonding between Sn and the surface (chemisorption), the "Sn-up" configuration is bound only by weak van der Waals forces (physisorption). By comparing our theoretical results with a broad range of experimental data, we assess the effect of dispersion forces for the SnPc/Ag(111) system and how these impact adsorption energies, geometries, and the electronic structure. We show that an inclusion of dispersion forces improves the adsorption geometry with respect to experiment and is essential in order to capture the subtle electronic effects at molecule-metal interfaces. By analyzing the geometric and electronic structure of the adsorbed molecules we, in addition, shed light on the surprising 2-fold symmetry reduction of metal phthalocyanine molecules that has been observed upon adsorption on surfaces

  • 2.
    Baran, Jakub D.
    et al.
    Tyndall National Institute, University College Cork.
    Larsson, Andreas
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Theoretical insights into adsorption of cobalt phthalocyanine on Ag(111): A combination of chemical and van der Waals bonding2013Ingår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 117, nr 45, s. 23887-23898Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this article we study in detail the interaction of cobalt phthalocyanine (CoPc) with the Ag(111) surface by means of density functional theory calculations (DFT). We discuss the electronic and geometric differences of the adsorbed CoPc as it interacts with the different binding sites of the surface, yielding deeper insight into the adsorption mechanism of organometallic molecules with noble metal surfaces. We interpret the experimentally observed 4-fold to 2-fold symmetry reduction upon interaction of phthalocyanine molecules with metal surfaces as caused by electronic effects originating from nonsymmetric interactions between the molecule and the surface. To asses the role of dispersion forces in bonding of CoPc to the surface we employ a semiempirical dispersion correction to standard DFT and compare the obtained molecule-surface separation with experimental measurements. We show that, in the case of CoPc, the molecule bonds to the surface mostly due to covalent bonding between Co and Ag, but with a considerable contribution from van der Waals bonding between the Pc ligand and the surface. We show in this case where the molecule-surface separation is mostly governed by covalent bonding between the central metal atom and the surface atoms that standard DFT performs reasonably well, as compared to the available experimental data.

  • 3.
    Carvalho, Alexandra
    et al.
    Department of Physics, University of Aveiro, Campus Santiago.
    Rayson, Mark
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    Briddon, Patrick R.
    Electrical, Electronic and Computer Engineering, University of Newcastle upon Tyne.
    Effect of oxidation on the doping of silicon nanocrystals with group III and group v elements2012Ingår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 116, nr 14, s. 8243-8250Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Substitutional group III and group V elements, though commonly used as shallow dopants in bulk silicon, have a limited efficiency in silicon nanocrystals. In this work, we use first-principles models of 1.5 nm nanocrystals with hydride- and silanol-terminated surfaces to understand how oxidation influences the segregation and deactivation of dopants at the surface and the dopant binding energies. We show that the surface oxygen layer changes drastically the radial dependence of the dopant formation energy both for donors and for acceptors, but that, independently from the oxidation, dopant diffusion does not take place at operating conditions. Additionally, we show that the oxidation increases the electron binding energy of the P, As, and Sb and decreases the hole binding energy of B, Al, Ga, and In.

  • 4.
    Czerwinski, Bartlomiej
    et al.
    Universite Catholique de Louvain, Institute of Condensed Matter and Nanosciences - Bio and Soft Matter, Louvain-la-Neuve.
    Delcorte, Arnaud
    Universite Catholique de Louvain, Institute of Condensed Matter and Nanosciences - Bio and Soft Matter, Louvain-la-Neuve.
    Molecular dynamics study of fullerite cross-linking under keV C 60 and Arn cluster bombardment2013Ingår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 117, nr 7, s. 3595-3604Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Molecular dynamics computer simulations are used to elucidate the cross-linking processes induced by 0.6-50 keV C60 and Arn cluster bombardment in a C60 fullerite solid sample. The obtained results indicate the presence of a "chemical effect" when C 60 projectile is used. Namely, the bombarding C60 delivers additional, highly reactive, radicals which interact with the atoms of the fullerite sample, increasing the efficiency of the cross-linking process. The omission of those interactions in the analysis makes the C60 very similar to the case of the Ar18 bombardment. For Arn cluster bombardment, the initial energy per atom in the projectile is the parameter which has the predominant influence on the cross-linking process. Furthermore, a relationship between the energy thresholds for fragmentation of the target molecules and cross-linking initiation and the size of the Ar clusters is observed. Both of these thresholds decrease with increasing size of the projectile.

  • 5.
    Dembele, Kadiatou Therese
    et al.
    Institut National de la Recherche Scientifique.
    Selopal, Gurpreet Singh
    CNR IDASC SENSOR Lab.
    Soldano, Caterina
    CNR IDASC SENSOR Lab.
    Nechache, Riad
    Institut National de la Recherche Scientifique.
    Rimada, Julio Cesar
    Solar Cells Laboratory, Institute of Materials Science and Technology (IMRE), University of Havana.
    Concina, Isabella
    CNR IDASC SENSOR Lab.
    Sberveglieri, Giorgio
    CNR IDASC SENSOR Lab.
    Rosei, Federico
    Institut National de la Recherche Scientifique.
    Vomiero, Alberto
    CNR IDASC SENSOR Lab.
    Hybrid carbon nanotubes-TiO2 photoanodes for high efficiency dye-sensitized solar cells2013Ingår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 117, nr 28, s. 14510-14517Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We describe a fast and effective procedure for the preparation of high efficiency hybrid photoanodes for dye-sensitized solar cells (DSCs), based on nanocrystalline TiO2 with limited addition of multiwall carbon nanotubes (CNTs). The mixing process between CNTs and TiO2 nanoparticles is almost instantaneous, which makes it feasible for large-scale fabrication. Enhanced electron lifetime and reduced charge recombination lead to highly increased short circuit current density and overall photoconversion efficiency (from 13.6 mA cm-2 to 16.0 mA cm-2 and from 7.0% to 9.0%, respectively, considering the bare TiO2 and the optimum CNTs concentration, which is 0.010 wt %), while the small reduction in open circuit photovoltage does not significantly affect cell performances. This result is remarkable since a standard dye molecule (N719) was used and no chemical treatments of the photoanodes prior to cell fabrication were applied (i.e., soaking in TiCl4 to boost open circuit photovoltage). © 2013 American Chemical Society.

  • 6.
    Dudenko, D.V.
    et al.
    Cardiff University.
    Williams, P.A.
    Cardiff University.
    Hughes, C.E.
    Cardiff University.
    Antzutkin, Oleg
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Velaga, Sitaram
    Luleå tekniska universitet, Institutionen för hälsovetenskap, Medicinsk vetenskap.
    Brown, S.P.
    University of Warwick.
    Harris, K.D.M.
    Cardiff University.
    Exploiting the synergy of powder x-ray diffraction and solid-state NMR spectroscopy in structure determination of organic molecular solids2013Ingår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 117, nr 23, s. 12258-12265Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We report a strategy for structure determination of organic materials in which complete solid-state nuclear magnetic resonance (NMR) spectral data is utilized within the context of structure determination from powder X-ray diffraction (XRD) data. Following determination of the crystal structure from powder XRD data, first-principles density functional theory-based techniques within the GIPAW approach are exploited to calculate the solid-state NMR data for the structure, followed by careful scrutiny of the agreement with experimental solid-state NMR data. The successful application of this approach is demonstrated by structure determination of the 1:1 cocrystal of indomethacin and nicotinamide. The 1H and 13C chemical shifts calculated for the crystal structure determined from the powder XRD data are in excellent agreement with those measured experimentally, notably including the two-dimensional correlation of 1H and 13C chemical shifts for directly bonded 13C-1H moieties. The key feature of this combined approach is that the quality of the structure determined is assessed both against experimental powder XRD data and against experimental solid-state NMR data, thus providing a very robust validation of the veracity of the structure

  • 7. Fredriksson, Andreas
    et al.
    Hellström, Pär
    Öberg, Sven
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    Holmgren, Allan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Comparison between in situ total internal reflection vibrational spectroscopy of an adsorbed collector and spectra calculated by ab initio density functional theory methods2007Ingår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 111, nr 26, s. 9299-9304Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this investigation, adsorbed heptyl xanthate on a Ge(111) surface was studied, as well as the free heptyl xanthate molecule, by means of first-principle density functional theory calculations. The modeled results were compared with the in situ total internal reflection vibrational spectroscopy spectra of heptyl xanthate adsorbed on a germanium internal reflection element and the transmission infrared spectrum of a heptyl xanthate ion in aqueous solution. The assignments of the vibrational frequencies were done for the adsorbed xanthate. The region between 1150 and 1000 cm(-1) seems suitable for discussing differences between an adsorbed xanthate and its corresponding ion. The modeled spectra for both the adsorbed xanthate and the xanthate ion are in good agreement with the experimentally retrieved spectra. This investigation shows the strength of using DFT calculations in the interpretation of absorption bands from molecules adsorbed at surfaces in situ.

  • 8.
    Gannon, Greg
    et al.
    Tyndall National Institute, University College Cork.
    Larsson, Andreas
    Thompson, Damien J.
    Tyndall National Institute, University College Cork.
    Monolayer packing, dehydration, and ink-binding dynamics at the molecular2009Ingår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 113, nr 17, s. 7298-7304Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Gold-bound self-assembled monolayers (SAMs) terminating in β-cyclodextrin (β-CD) cavities provide a highly ordered surface array of hydrophobic binding pockets and so are used as "molecular printboards" for nanopatterning applications. The present work complements ongoing nanoscale experiments by providing the atom-scale structure, dynamics, and energetics of the printboard, which may aid the design of functional platforms for nanotechnology. We use fully atomistic molecular dynamics (MD) computer simulations to probe the printboard lattice constant, height, steric packing, hydrophobicity, and ink-binding properties as a function of gold-β-CD "linker" molecule and degree of binding to gold. The simulations reveal the stabilization associated with the experimentally observed surface lattice constant of ∼2 nm, alkanethioether linkers, and partial unbinding from gold. Additional ink-binding simulations indicate that multivalent ink molecules can offset disordering in the more loosely packed alkanethiol-linked printboard, with the attendant steric penalty similar in magnitude to the favorable multivalent ink:β-CD complexation

  • 9.
    Grahn, Mattias
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Holmgren, Allan
    Hedlund, Jonas
    Adsorption of n-hexane and p-xylene in thin silicalite-1 films studied by FTIR/ATR spectroscopy2008Ingår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 112, nr 20, s. 7717-7724Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Adsorption isotherms for p-xylene and n-hexane in silicalite-1 films with a thickness of 200 nm were determined at 323, 343, 368, 393, and 423 K using Fourier transform infrared/attenuated total reflection (FTIR/ATR) spectroscopy. For both adsorbates, the low-pressure data agreed with literature data for MFI powder and the estimated Henry's constant and adsorption enthalpy were close to previously reported results. The upper region of the n-hexane isotherm (p > 2 kPa at 323 K) was likely influenced by micropores in open grain boundaries, as expected for a polycrystalline film of small (<200 nm) crystals. As for n-hexane, the first part (0 ≤ p ≤ 65 Pa at 323 K) of the p-xylene isotherm agreed with data for powder. However, the saturation capacity was only about half of that previously reported for powders, which indicates that p-xylene molecules do not adsorb in the sinusoidal channels in the film. We speculate that the small crystals used in the present work may behave differently from the larger crystals in previous works. Another explanation for the lower saturation capacity may be the bonding of crystals to the supports, which are known to induce strain in the attached crystals.

  • 10.
    Heikkinen, Olli
    et al.
    Department of Applied Physics, Aalto University School of Science.
    Pinto, H.
    School of Physics, University of Exeter, College of Engineering, Mathematics and Physical Sciences, University of Exeter, Department of Physics, University of Minho, Campus de Gualtar, 4710-553 Braga, Hungarian Academy of Sciences, Wigner Research Centre for Physics, Institute for Solid State Physics and Optics, COMP Centre of Excellence, Department of Applied Physics, Aalto University School of Science.
    Sinha, Godhuli
    Department of Applied Physics, Aalto University School of Science.
    Hämäläinen, Sampsa K.
    Department of Applied Physics, Aalto University School of Science.
    Sainio, Jani P.
    Department of Applied Physics, Aalto University School of Science.
    Öberg, Sven
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Briddon, Patrick R.
    Department of Physics, University of Newcastle, School of Electrical, Electronic and Computer Engineering, University of Newcastle upon Tyne, School of Natural Science, University of Newcastle upon Tyne.
    Foster, Adam S.
    COMP Centre of Excellence, Department of Applied Physics, Aalto University School of Science.
    Lahtinen, Jouko
    Department of Applied Physics, Aalto University School of Science.
    Characterization of a Hexagonal Phosphorus Adlayer on Platinum (111)2015Ingår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 119, nr 22, s. 12291-12297Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Platinum is a well-known catalytic metal whose efficiency can be degraded by the adsorption of impurities. Using different characterization techniques, such as scanning tunnelling microscopy, low-energy electron diffraction, and X-ray photoelectron spectroscopy, we present a study of phosphorus adsorption on a platinum (111) surface. Under saturation and after annealing at 750 °C, phosphorus was observed to form an ordered hexagonal adlayer with a (4√3 × 4√3)-R30° symmetry. On the basis of density functional theory calculations, we propose a model for the phosphorus adlayer, consisting of either P13 or P14 clusters. In addition, carbon monoxide adsorption as a function of the phosphorus coverage was also investigated. We found that the phosphorus adlayer prevents carbon monoxide adsorption on Pt(111) reducing its catalytic efficiency. (Figure Presented

  • 11. Hellström, Pär
    et al.
    Holmgren, Allan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Öberg, Sven
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    An ab initio study of ethyl xanthate adsorbed on Ge(111) surfaces2007Ingår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 111, nr 45, s. 16920-16926Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The interaction between adsorbed ethyl xanthate on a clean Ge(111) surface and a hydroxylated surface was studied, using first-principle density functional theory. Geometrically optimized structures are presented and discussed. Results suggest a bidentate bridging conformation on a clean Ge(111) surface, whereas a monodentate bonding is preferred when the surface is saturated by hydrogen atoms. Then the interaction with a hydroxylated surface was considered. The lowest energy configuration was obtained when xanthate binds with one sulfur to the surface and with the other to an OH group adsorbed on the surface. A marker for this configuration was found in the vibrational spectra at 3200 cm-1. Vibrational frequencies down to 250 cm-1 were calculated and assigned to vibrational modes and presented together with the calculated infrared spectra. The tilt angle of the hydrocarbon chain was also investigated.

  • 12.
    Holmgren, Allan
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Yang, Xiaofang
    A polarized Fourier transform infrared spectrometry attenuated total reflection study of bentonite settled onto magnetite2008Ingår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 112, nr 42, s. 16609-16615Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Sodium bentonite in aqueous suspension was allowed to settle onto a layer of magnetite, and the orientation of the bentonite platelets was monitored using the Fourier transform infrared spectrometry-attenuated total reflection technique. This study is the first reported use of polarized IR to study the in situ settling of delaminated bentonite platelets onto a thin layer of magnetite nanoparticles. The experiment was performed at a pH value (pH 5.6) close to the point of zero charge for the edge surfaces of the bentonite platelets in order to possibly enhance the probability for the (001) surface of bentonite to adhere to the positively charged magnetite particles. The order parameter (S) of the platelets was calculated both for the dry film and the film formed during water evaporation. These results were compared with the orientation of bentonite platelets on the internal reflection element (ZnSe) without magnetite particles, a system where the three layer model is valid. During settling of the bentonite, the tilt angle of the normal to the (001) surface of the platelets decreases and reaches a minimum value for the dry film. When the film is still covered by a layer of water, the tilt angles indicate the film to be at least partly built up of so-called card-house structures, implying that the edge surfaces of the platelets are at least partly adhering to the basal (001) surfaces.

  • 13.
    Jarvis, Samuel P.
    et al.
    School of Physics and Astronomy, University of Nottingham.
    Taylor, Simon
    School of Physics and Astronomy, University of Nottingham.
    Baran, Jakub D.
    Tyndall National Institute, University College Cork, School of Chemistry, University of Bath, Department of Chemistry, University of Bath.
    Thompson, Damien
    Department of Physics and Energy, Materials and Surface Science Institute, University of Limerick.
    Saywell, Alex
    Fritz Haber Institute of the Max-Planck Society, School of Physics and Astronomy, University of Nottingham.
    Mangham, Berry
    School of Chemistry, the University of Nottingham.
    Champness, Neil R.
    School of Chemistry, the University of Nottingham.
    Larsson, Andreas
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Moriarty, Philip
    School of Physics and Astronomy, University of Nottingham.
    Physisorption Controls the Conformation and Density of States of an Adsorbed Porphyrin2015Ingår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 119, nr 50, s. 27982-27994Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Conformational changes caused by adsorption can dramatically affect a molecule's properties. Despite extensive study, however, the exact mechanisms underpinning conformational switching are often unclear. Here we show that the conformation of a prototypical flexible molecule, the free-base tetra(4-bromophenyl) porphyrin, adsorbed on Cu(111), depends critically on its precise adsorption site and that, remarkably, large conformational changes are dominated by van der Waals interactions between the molecule and the substrate surface. A combination of scanning probe microscopy, single-molecule manipulation, DFT with dispersion density functional theory, and molecular dynamics simulations show that van der Waals forces drive significant distortions of the molecular architecture so that the porphyrin can adopt one of two low-energy conformations. We find that adsorption driven by van der Waals forces alone is capable of causing large shifts in the molecular density of states, despite the apparent absence of chemical interactions. These findings highlight the essential role that van der Waals forces play in determining key molecular properties.

  • 14.
    Li, Zhong
    et al.
    Department of Chemistry, Materials Section and Supercritical Fluid Centre, University College Cork.
    Larsson, Andreas
    Larsson, Peter O.
    Department of Physics, Condensed Matter Theory Group, Uppsala University.
    Ahuja, Rajeev B.
    Department of Physics, Condensed Matter Theory Group, Uppsala University.
    Tobin, Joseph M.
    Department of Chemistry, Materials Section and Supercritical Fluid Centre, University College Cork.
    O'Byrne, Justin P.
    Department of Chemistry, Materials Section and Supercritical Fluid Centre, University College Cork.
    Morris, Michael A.
    Department of Chemistry, Materials Section and Supercritical Fluid Centre, University College Cork.
    Attard, Gary Anthony
    School of Chemistry, Cardiff University.
    Holmes, Justin D.
    Department of Chemistry, Materials Section and Supercritical Fluid Centre, University College Cork.
    Copper/molybdenum nanocomposite particles as catalysts for the growth of bamboo-structured carbon nanotubes2008Ingår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 112, nr 32, s. 12201-12206Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Bamboo-structured carbon nanotubes (BCNTs), with mean diameters of 20 nm, have been synthesized on MgO-supported Cu and Mo catalysts by the catalytic chemical vapor deposition of methane. BCNTs could only be generated using a combination of Cu and Mo catalysts. No BCNTs were produced from either individual Cu or Mo catalysts. In combination, Mo was found to be essential for cracking the methane precursor, while Cu was required for BCNT formation. Energy dispersive X-ray analysis of the individual particles at the tips of the nanotubes suggest that Cu and Mo are present as a "composite" nanoparticle catalyst after growth. First-principles modeling has been used to describe the interaction of the Cu/Mo catalyst with the nanotubes, suggesting that the catalyst binds with the same energy as traditional catalysts such as Fe, Ni, and Co

  • 15.
    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.
    He, Jian
    Intelligent Composites Laboratory, Department of Chemical and Biomolecular Engineering, The University of Akron.
    Li, Yifan
    Intelligent Composites Laboratory, Department of Chemical and Biomolecular Engineering, The University of Akron.
    Ji, Tuo
    Intelligent Composites Laboratory, Department of Chemical and Biomolecular Engineering, The University of Akron.
    Mehra, Nitin
    Intelligent Composites Laboratory, Department of Chemical and Biomolecular Engineering, The University of Akron.
    Shi, Yijun
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Zhu, Jiahua
    Intelligent Composites Laboratory, Department of Chemical and Biomolecular Engineering, The University of Akron.
    Molecular Origin of Efficient Phonon Transfer in Modulated Polymer Blends: Effect of Hydrogen Bonding on Polymer Coil Size and Assembled Microstructure2017Ingår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 121, nr 26, s. 14204-14212Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Molecular level engineering of polymer or polymer blends has been recently demonstrated effective strategy to regulate thermal conductivity. Such materials are of great interest to meet critical requirements of transparent, light weight, flexible, etc for thermal management in electronic applications. In this work, modulated polymer blends with poly(vinyl alcohol) (PVA) and biopolymers (lignin, gelatin) were designed and significantly enhanced thermal conductivity was achieved by tuning the intermolecular interaction among polymer components. The hydrogen bond interaction has been revealed as the major driving force that affects the polymer coil dimension in aqueous solution, the microstructure of coil-coil interaction in solid film and thus the thermal conduction. A solid relationship across molecular level interaction to macro-scale thermal conduction is constructed via careful characterization of the coil size in liquid phase and assembled microstructure in solid phase. Appropriate integration of biopolymers and PVA is essential to achieve synergistic effect. Specifically, thermal conductivity of polymer blend with 10% lignin and 10% G90 in PVA reaches 0.71 W/m·K, which is 184% enhancement as compared to pure PVA. This work reveals the fundamental molecular origin of polymer blends in association with thermal conductivity and has great potential to guide molecular engineering for superior physicochemical properties.

  • 16.
    Muthukumar, Kaliappan
    et al.
    Tyndall National Institute, University College Cork.
    Stróżecka, Anna
    Peter Grünberg Institut (PGI-3), and JARA-Fundamentals of Future Information Technology, Forschungszentrum Jülich.
    Mysliveček, Josef
    Charles University, Faculty of Mathematics and Physic.
    Dybek, Aneta
    Department of Physics, Queen Mary University of London.
    Dennis, John S.
    Department of Physics, Queen Mary University of London.
    Voigtländer, Bert
    Peter Grünberg Institut (PGI-3), and JARA-Fundamentals of Future Information Technology, Forschungszentrum Jülich.
    Larsson, Andreas
    Endohedral Fullerene Ce@C82 on Cu(111: Orientation, Electronic Structure, and Electron-Vibration Coupling2013Ingår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 117, nr 4, s. 1656-1662Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Structural, electronic, and vibrational properties of the endohedral fullerene Ce@C82 on Cu(111) have been studied by scanning tunneling microscopy (STM) and density functional theory (DFT). Ce@C82 forms islands on the substrate. Our STM measurements show relatively large differences in morphology and electron spectra of molecules within these islands indicating multiple molecular orientations on the substrate, while the vibrational spectra are more uniform. We have determined molecular orientations by comparing STM and DFT molecular morphology, and we have calculated Ce@C82 bound to Cu(111) and found that it is chemisorbed. We show that Ce@C82 adopts orientations on the surface that enables Ce to remain at its most favorable binding site inside C82. The effect of chemisorption on the structural and electronic properties of Ce@C82 is thus small, and the orientations are limited to configurations with Ce in the upper hemisphere of the molecular configurational space. We show that the variations in the dI/dV spectra between molecules of different orientations is due to Ce-cage orbitals that are localized in space and their involvement in tunneling depends on the molecular orientation on the substrate. The observed electron-vibration coupling modes in the STM-IETS (in-elastic tunneling spectroscopy) of Ce@C82 arise from cage modes only, and therefore, electron transport properties are expected to be different compared to Ce2@C80, which has active Ce-cage vibrations.

  • 17.
    O'Byrne, Justin P.
    et al.
    Department of Chemistry, Tyndall National Institute, University College Cork.
    Li, Zhong
    Department of Chemistry, Tyndall National Institute, University College Cork.
    Tobin, Joseph M.
    Department of Chemistry, Tyndall National Institute, University College Cork.
    Larsson, Andreas
    Larsson, Peter O.
    Department of Physics, Condensed Matter Theory Group, Uppsala University.
    Ahuja, Rajeev B.
    Department of Physics, Condensed Matter Theory Group, Uppsala University.
    Holmes, Justin D.
    Department of Chemistry, Tyndall National Institute, University College Cork.
    Growth of carbon nanotubes from heterometallic palladium and copper catalysts2010Ingår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 114, nr 18, s. 8115-8119Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Bamboo-structured carbon nanotubes (BCNTs) were synthesized with MgO-supported Pd and Cu catalysts, doped with either Mo or W, by the catalytic chemical vapor decomposition of methane. No nanotubes were observed to grow from the catalysts in the absence of the dopant metals. Additionally, the level of dopant in the catalysts was found to strongly affect the morphology of carbon produced. Amorphous carbon was generated on a 10 wt % Cu/5 wt % W (2:1) catalyst, while BCNTs were produced on 20 wt % Cu/5 wt % W (4:1) and a 30 wt % Cu/5 wt % W (6:1) catalysts. A pure Pd catalyst produced carbon nanofibres (CNFs), while BCNTs were able to grow from Pd/Mo catalysts. Density functional theory simulations show that the composite Cu/W and Pd/Mo bimetallic particles which generated BCNTs have similar binding energies to carbon, and comparable to metals such as Fe, Co, and Ni which are traditionally used to grow CNTs by chemical vapor deposition

  • 18.
    Ohlin, Lindsay
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Bazin, Philippe
    Thibault-Starzyk, Frederic
    Hedlund, Jonas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Grahn, Mattias
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Adsorption of CO2, CH4, and H2O in zeolite ZSM-5 studied using in situ ATR-FTIR spectroscopy2013Ingår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 117, nr 33Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Biogas and natural gas are interesting fuels with high H/C ratio. However, these gases frequently contain carbon dioxide and water which lowers the heat value of the gas and may induce corrosion. Therefore, the development of more efficient processes, such as membrane processes and improved adsorbents, for the separation of carbon dioxide and water from biogas and natural gas is of great importance. Zeolite ZSM-5 membranes are promising for this separation which is controlled by the adsorption and diffusion of the different species in the zeolite. Multicomponent adsorption data are therefore required for development of new membrane and adsorption processes. In the present work, the adsorption of water, carbon dioxide, and methane in a Na-ZSM-5 zeolite film at various temperatures was studied by in situ Attenuated Total Reflectance-Fourier Transform Infrared (ATR-FTIR) spectroscopy for the first time. Adsorption isotherms were retrieved from the experimental data and the Langmuir model fitted the isotherms very well. Limiting heat of adsorption was determined from the Henrýs law regime and the values determined agreed well with previously reported data. A few experiments were conducted with multicomponent mixtures and the experimentally determined amounts adsorbed were compared with values predicted by the Ideal Adsorbed Solution Theory (IAST). It was found that for the binary mixture of carbon dioxide and methane there was good agreement between the experimental values and those predicted by the IAST. However, when water was also introduced, the IAST could not fully capture the adsorption behavior of the multicomponent mixture, probably because the adsorbed phase is not ideal. These findings are in line with previous reports for adsorption in zeolites. The multicomponent adsorption behavior of this system will be further investigated in forthcoming work.

  • 19.
    Ohlin, Lindsay
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Berezovsky, Vladimir
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Öberg, Sven
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Farzaneh, Amirfarrokh
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Holmgren, Allan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Grahn, Mattias
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Effect of Water on the Adsorption of Methane and Carbon Dioxide in Zeolite Na-ZSM-5 Studied Using in Situ ATR-FTIR Spectroscopy2016Ingår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 120, nr 51, s. 29144-29152Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Methane is the main component in biogas and natural gas along with contaminants such as water and carbon dioxide. Separation of methane from these contaminants is therefore an important step in the upgrading process. Zeolite adsorbents and zeolite membranes have great potential to be cost-efficient candidates for upgrading biogas and natural gas, and in both of these applications, knowing the nature of the competitive adsorption is of great importance to further develop the properties of the zeolite materials. The binary adsorption of methane and carbon dioxide in zeolites has been studied to some extent, but the influence of water has been much less studied. In the present work, in situ ATR (attenuated total reflection)–FTIR (Fourier transform infrared) spectroscopy was used to study the adsorption of water/methane and water/carbon dioxide from binary mixtures in a high-silica Na-ZSM-5 zeolite film at various gas compositions and temperatures. Adsorbed concentrations for all species were determined from the recorded IR spectra, and the experimental values were compared to values predicted using the ideal adsorbed solution theory (IAST). At lower temperatures (35, 50, and 85 °C), the IAST was able to predict the binary adsorption of water and methane, whereas the values predicted by the IAST deviated from the experimental data at the highest temperature (120 °C). For the binary adsorption of water and carbon dioxide, the IAST could not predict the adsorption values accurately. This discrepancy was assigned to the particular adsorption behavior of water in high-silica MFI forming clusters at hydrophilic sites. However, the predicted values did follow the same trend as the experimental values. The adsorption selectivity was determined, and it was found that the H2O/CH4 adsorption selectivity was decreasing with increasing water content in the gas phase at low temperatures whereas the selectivity was increasing at higher temperatures. The H2O/CO2 adsorption selectivity was increasing with increasing water content at all temperatures.

  • 20.
    Ohlin, Lindsay
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Farzaneh, Amirfarrokh
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Holmgren, Allan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Hedlund, Jonas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Grahn, Mattias
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Ternary Adsorption of Methane, Water and Carbon Dioxide in Zeolite Na-ZSM-5 Studied Using in Situ ATR-FTIR Spectroscopy2017Ingår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 121, nr 27, s. 14703-14711Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The main component in biogas and natural gas is methane but these gases also contain water and carbon dioxide that often have to be removed in order to increase the calorific value of the gas. Membrane and adsorbent-based technologies using zeolites are interesting alternatives for efficient separation of these components. To develop efficient processes, it is essential to know the adsorption properties of the zeolite. In the present work, adsorption of methane, carbon dioxide and water from ternary mixtures in high silica zeolite Na-ZSM-5 was studied using in-situ ATR (Attenuated Total Reflection) – FTIR (Fourier Transform Infrared) spectroscopy. Adsorbed concentrations were extracted from the infrared spectra and the obtained loadings were compared to values predicted by the Ideal Adsorbed Solution Theory (IAST). The IAST could not fully capture the adsorption behavior of this ternary mixture, indicating that the adsorbed phase is not behaving as an ideal mixture. The CO2/CH4 adsorption selectivities determined for the ternary mixtures were compared to selectivities determined for binary mixtures in our previous work, indicating that the presence of water slightly improves the CO2/CH4 adsorption selectivity at lower temperatures. Further, the results show that water and carbon dioxide are adsorbed preferentially over methane in high silica zeolite Na-ZSM-5.

  • 21.
    Ohlin, Lindsay
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Grahn, Mattias
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Detailed Investigation of the Binary Adsorption of Carbon Dioxide and Methane in Zeolite Na-ZSM-5 Studied Using in Situ ATR-FTIR Spectroscopy2014Ingår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 118, nr 12, s. 6207-6213Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The separation of carbon dioxide from methane is an important process when purifying biogas and natural gas. Zeolite membranes and adsorbents are among the technologies suggested for efficient separation of carbon dioxide from these gases. In the present work, the adsorption of carbon dioxide and methane from binary mixtures in a low alumina Na-ZSM-5 zeolite film at various gas compositions and temperatures was studied using in situ ATR-FTIR (attenuated total reflection Fourier transform infrared) spectroscopy. Adsorbed concentrations were successfully extracted from infrared spectra. The experimental values of the adsorbed phase mole fraction of carbon dioxide and methane were compared to values predicted using the ideal adsorbed solution theory (IAST). The values predicted with the IAST agreed very well with values determined experimentally. The CO2/CH4 adsorption selectivity was determined, and at 35 °C a selectivity of 15.4 was obtained for an equimolar gas mixture. At the highest (0.9) and lowest (0.03) investigated mole fractions of carbon dioxide in the gas phase, the selectivity was higher compared to the other investigated mole fractions. At 35 °C the highest observed selectivity values were 31.1 and 20.4 for the highest and the lowest adsorbed mole fraction, respectively. At compositions closest to those found in biogas and natural gas, there was a decrease in the selectivity at higher temperatures, indicating that separation of carbon dioxide from methane in biogas and natural gas may be more efficient at low temperatures

  • 22.
    Shah, Faiz Ullah
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Holmgren, Allan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Rutland, Mark W.
    Surface and Corrosion Science, Department of Chemistry, KTH Royal Institute of Technology.
    Glavatskih, Sergei
    System and Component Design, KTH Royal Institute of Technology.
    Antzutkin, Oleg
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik. Department of Physics, University of Warwick.
    Interfacial Behavior of Orthoborate Ionic Liquids at Inorganic Oxide Surfaces Probed by NMR, IR and Raman Spectroscopy2018Ingår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 122, nr 34, s. 19687-19698Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Absorption modes and reactivity of non-halogenated ionic liquids (ILs) at inorganic oxide surfaces of γ-Al2O3, MgO and SiO2 particles were characterized using multinuclear (11B, 31P and 29Si) solid-state magic-angle-spinning NMR, FTIR and Raman spectroscopy. ILs are composed of the trihexyl(tetradecyl)phosphonium cation, [P6,6,6,14]+, and bis(mandelato)borate, [BMB]-, or bis(salicylato)borate, [BScB]-, anions. Spectroscopic measurements were performed on room temperature (298 K) samples and samples exposed to 15 hours of heating at 373 K. The single pulse 11B NMR data of heated [P6,6,6,14][BMB] mixed with the inorganic oxides showed a significant change in spectra of the anion for all three oxides. In contrast, no such spectral changes were detected for heated [P6,6,6,14][BScB] mixed with the inorganic oxides. 31P MAS NMR data for the IL/metal oxide systems revealed interactions between [P6,6,6,14]+ and the surfaces of oxides. A significant intensity of 31P CP-MAS NMR signals indicated a low mobility of cations in these systems. The existence of strongly adhered surface layers of ILs on SiO2 particles was also confirmed by 1H-29Si CP-MAS NMR spectroscopy. FTIR and Raman spectroscopic data revealed strong interactions between the anions and the inorganic surfaces and there is strong correlation with the data obtained from NMR spectroscopy. Although their chemical structures are rather similar, the [BScB]- anion is more stable than the [BMB]- anion at the inorganic oxide surface.

  • 23.
    Shen, Gulou
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap. Jiangsu Provincial Engineering Laboratory for Advanced Materials of Salt Chemical Industry, Huaiyin Institute of Technology, Huaian.
    Laaksonen, Aatto
    Stockholm University, Arrhenius Laboratory, Department oft Materials & Environmental Chemistry.
    Lu, Xiaohua
    Key Laboratory of Material and Chemical Engineering, Nanjing Tech University, Nanjing .
    Ji, Xiaoyan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Developing Electrolyte Perturbed-Chain Statistical Associating Fluid Theory Density Functional Theory for CO2 Separation by Confined Ionic Liquids2018Ingår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 122, nr 27, s. 15464-15473Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The electrolyte perturbed-chain statistical associating fluid theory (ePC-SAFT) classical density functional theory (DFT) was developed to describe the behavior of pure ionic liquid (IL) and CO2/IL mixture confined in nanopores, in which a new ionic functional based on the ionic term from ePC-SAFT was proposed for electrostatic free-energy contribution. The developed model was verified by comparing the model prediction with molecular simulation results for ionic fluids, and the agreement shows that the model is reliable in representing the confined behavior of ionic fluids. The developed model was further used to study the behavior of pure IL and CO2/IL mixture in silica nanopores where the IL ions and CO2 were modeled as chains that consisted of spherical segments with the parameters taken from the bulk ePC-SAFT. The results reveal that the nanoconfinement can lead to an increased CO2 solubility, and the solubility increases with increasing pressure. The averaged density of pure IL and solubility of CO2 are strongly dependent on pore sizes and geometries. In addition, the choice of IL ions is very important for the CO2 solubility. Overall, the modeling results for silica-confined systems are consistent with available molecular simulation and experimental results.

  • 24.
    Vigolo, Birgitte
    et al.
    Nancy Université.
    Vincent, Brice
    Nancy Université.
    Eschbach, Julien
    Nancy Université.
    Bourson, Patrice
    University of Metz & Supelec.
    Mareche, Jean-Francois
    Nancy Université.
    McRae, Edward
    Nancy Université.
    Müller, Andreas
    Luleå tekniska universitet.
    Soldatov, Alexander
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Hiver, Jean-Marie
    Nancy Université.
    Dahoun, Abdesselam
    Nancy Université.
    Rouxel, Didier
    Nancy Université.
    Multiscale characterization of single-walled carbon nanotube/polymer composites by coupling Raman and Brillouin spectroscopy2009Ingår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 113, nr 41, s. 17648-17654Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The present paper reports on an original experimental approach to the characterization of SWNT/polymer composites. This work deals with the multiscale characterization of nanocomposites. Covalently functionalized SWNTs were incorporated in a PMMA matrix using an in situ polymerization procedure. We show that their presence does not affect the radical polymerization process. Combining Brillouin and Raman spectroscopy, we were able to associate the obtained mechanical properties of the material at the macroscopic scale to the state of functionalization of the SWNTs within the polymer matrix.

  • 25.
    Zarshenas, Mohammad
    et al.
    Institute of Condensed Matter and Nanosciences - Bio & Soft Matter (IMCN/BSMA), Université Catholique de Louvain.
    Moshkunov, Konstantin
    Institute of Condensed Matter and Nanosciences - Bio & Soft Matter (IMCN/BSMA), Université Catholique de Louvain.
    Czerwinski, Bartlomiej
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Leyssens, Tom
    Institute of Condensed Matter and Nanosciences - Molecules, Solids and Reactivity (IMCN/MOST) Université Catholique de Louvain.
    Delcorte, Amaud
    Institute of Condensed Matter and Nanosciences - Bio & Soft Matter (IMCN/BSMA), Université Catholique de Louvain.
    Molecular Dynamics Simulations of Hydrocarbon Film Growth from Acetylene Monomers and Radicals: Effect of Substrate Temperature2018Ingår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 122, nr 27, s. 15252-15263Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In an attempt to rationalize the mechanisms occurring during plasma polymerization of acetylene, classical molecular dynamics (MD) computer simulations investigating the deposition and reaction of a mixed gas of acetylene molecules and radicals on the Ag(111) substrate were performed for a wide range of substrate temperatures. Prior to that, this article establishes a methodology for film deposition and identifies the appropriate potentials for hydrocarbons by comparison with electronic calculations using the density functional theory (DFT). Based on this preliminary study, simulations of films growth are carried out at different temperatures using the REBO potential. Our results show that the rates of creation of new C-C and C-H bonds are higher at the beginning of the film growth when the substrate is still exposed, than when it is covered with polymeric chains, and these initial reaction rates are proportional to temperature. The analysis of the hybridization of carbon atoms in the films shows that the substrate temperature increase leads to the formation of coatings containing more carbon atoms in the sp2 and sp3 configurations and less in the sp configuration with sp2 becoming dominant at high temperatures. We establish a polymerization-connectivity formalism that describes the structural transformation of the film during the deposition on the basis of each atom hybridization and bonding. Within this formalism the evolution of the polymerization and the connection character of the polymers is observed and discussed.

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