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  • 1. Abid, Jean-Pierre
    et al.
    Abid, Mohamed
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet.
    Bauer, Christophe
    Girault, Hubert H.
    Brevet, Pierre-Francois
    Controlled reversible adsorption of core: Shell metallic nanoparticles at the polarized water/1,2-dichloroethane interface investigated by optical second-harmonic generation2007Inngår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 111, nr 25, s. 8849-8855Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We report the observation of the reversible adsorption of core-shell gold-silver nanoparticles at the polarized water/1,2-dichloroethane interface using the nonlinear optical technique of surface second-harmonic generation. This study unambiguously demonstrates the excellent stability against aggregation of these core-shell nanoparticles, namely, gold core nanoparticles coated with silver layers of variable thickness, in the presence of an electrolyte salt like lithium chloride. Furthermore, it is also demonstrated that the adsorption of the nanoparticles is reversible by modulating the applied potential at water/1,2-dichloroethane interface. The analysis of these results is performed within the Debye-Huckel approximation of the electrostatic interactions between the nanoparticles. This approach shows that the stability of core-shell nanoparticles can be attributed to the formation of a silver oxide layer at the Surface of the particles.

  • 2.
    Abou-Hamad, Edy
    et al.
    Universite Montpellier II.
    Kim, Y
    University of Pennsylvania.
    Talyzin, Alexandr
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Fysik.
    Goze-Bac, Christophe
    Universite Montpellier II.
    Luzzi, David
    University of Pennsylvania.
    Rubio, Angelo
    University of Basque Country.
    Wågberg, Thomas
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Fysik.
    Hydrogenation of C-60 in Peapods: Physical Chemistry in Nano Vessels2009Inngår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 113, nr 20, s. 8583-8587Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Hydrogenation of C-60 molecules inside SWNT was achieved by direct reaction with hydrogen gas at elevated pressure and temperature. Evidence for the C-60 hydrogenation in peapods is provided by isotopic engineering with specific enrichment of encapsulated species and high resolution C-13 and H-1 NMR spectroscopy with the observation of characteristic diamagnetic and paramagnetic shifts of the NMR lines and the appearance of sp(3) carbon resonances. We estimate that approximately 78% of the C-60 molecules inside SWNTs are hydrogenated to an average degree of 14 hydrogen atoms per C-60 molecule. As a consequence, the rotational dynamics of the encapsulated C60Hx molecules is clearly hindered. Our successful hydrogenation experiments open completely new roads to understand and control confined chemical reactions at the nano scale

  • 3.
    Agrios, Alexander G.
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för fysikalisk och analytisk kemi, Fysikalisk kemi.
    Hagfeldt, Anders
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för fysikalisk och analytisk kemi, Fysikalisk kemi.
    Low-temperature TiO2 Films for Dye-sensitized Solar Cells: Factors Affecting Energy Conversion Efficiency2008Inngår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 112, nr 27, s. 10021-10026Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Semiconductor films prepd. by electrostatic layer-by-layer deposition can be used to fabricate dye-sensitized solar cells after low-temp. treatment (150 DegC). However, the resulting photocurrent is much less than when the film is sintered at 500 DegC. The difference in short-circuit current is a factor of 2.2 with the Ru-based dye N719 and is 3.5 with the org. dye D5. The photocurrent at a given wavelength is proportional to the light-harvesting efficiency, charge injection effciency, and charge collection efficiency. Sintered films take up more than 60% more of either dye than unsintered films and therefore absorb more photons. Electron injection is hindered in unsintered films due to a conduction band edge potential 100 mV more neg. than in a sintered electrode. Addnl. injection effects could be due to adsorption of the dye to polymer rather than to TiO2 in unsintered films, although our measurements were inconclusive on this point. Kinetic studies show electron transport times (ttr) an order of magnitude faster then electron lifetimes (te) in both sintered and unsintered electrodes. Furthermore, a Li+ insertion expt. shows that both films have good elec. connectivity between TiO2 nanoparticles. Unsintered films thus exhibit efficient charge transport despite the presence of polymer and the lack of heat treatment to induce necking.

  • 4. Ahlund, John
    et al.
    Nilson, Katharina
    Palmgren, Pål
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Gothelid, Emmanuelle
    Schiessling, Joachim
    Göthelid, Mats
    Martensson, Nils
    Puglia, Carla
    Molecular growth determined by surface domain patterns2008Inngår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 112, nr 17, s. 6887-6890Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The growth of iron phthalocyanine (FePc) on InSb(001) c(8 x 2) at submonolayer coverage has been investigated with scanning tunneling microscopy (STM). FePc adsorbs flat centered on the In rows both at 70 K and at room temperature (RT). However, the shapes of the two-dimensional molecular islands are fundamentally different; while the RT growth results in chainlike structures along the [I 10] direction, as already observed for other Pc's adsorbed on the same surface, the islands are prolonged along [110], i.e., perpendicular to the substrate rows, at 70 K. These observations are explained on the basis of a recently observed new surface phase at low temperature, resulting in structural domains on the surface. The molecular growth front follows the propagating domain boundary that freezes at low temperature.

  • 5. Ahmad, Y.
    et al.
    Dubois, M.
    Guerin, K.
    Hamwi, A.
    Fawal, Z.
    Kharitonov, A. P.
    Generalov, A. V.
    Klyushin, A. Yu.
    Simonov, K. A.
    V.A. Fock Institute of Physics, St. Petersburg State University, St. Petersburg 198504, Russia.
    Vinogradov, Nikolay A.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Molekyl- och kondenserade materiens fysik. V.A. Fock Institute of Physics, St. Petersburg State University, St. Petersburg 198504, Russia.
    Zhdanov, I. A.
    V.A. Fock Institute of Physics, St. Petersburg State University, St. Petersburg 198504, Russia.
    Preobrajenski, A. B.
    MAX-lab, Lund University, Box 118, 22100 Lund, Sweden.
    Vinogradov, A. S.
    V.A. Fock Institute of Physics, St. Petersburg State University, St. Petersburg 198504, Russia.
    NMR and NEXAFS Study of Various Graphite Fluorides2013Inngår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 117, nr 26, s. 13564-13572Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Graphite fluorides with different structural types (CyF)(n) (y = 2.5, 2, and 1) and room temperature graphite fluorides were studied by solid state,NMR and NEXAFS. Data extracted from those two techniques are complementary, providing information about the C-F bonding and the hybridization character of the carbon atom valence states. The comparison of data obtained by different methods such as NMR, Raman, and X-ray absorption leads to similar conclusions regarding the chemical bonding in fluorographites. Several major configurations of fluorinated graphites are discussed, that is, planar sheets with mainly sp(2) hybridization in room temperature graphite fluorides and corrugated sheets with sp(3) hybridization in covalent high temperature graphite fluoride. Different references such as highly oriented pyrolytic graphite (HOPG), graphitized carbon nanodiscs (graph-CNDs) and nanodiamonds (NDs) have also been investigated for comparison.

  • 6. Ai, Yuejie
    et al.
    Li, Xin
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Ji, Yongfei
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Song, Wei-Guo
    Luo, Yi
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Hydrophobicity and Hydrophilicity Balance Determines Shape Selectivity of Suzuki Coupling Reactions Inside Pd@meso-SiO2 Nanoreactor2016Inngår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 120, nr 19, s. 10244-10251Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Molecular sorting and catalysis directed by shape selectivity have been extensively applied in porous extended frameworks for a low-carbon, predictable, renewable component of modern industry. A comprehensive understanding of the underlying recognition mechanism toward different shapes is unfortunately still missing, owing to the lack of structural and dynamic information under operating conditions. We demonstrate here that such difficulties can be overcome by state-of-the-art molecular dynamics simulations which provide atomistic details that are not accessible experimentally, as exemplified by our interpretation for the experimentally observed aggregation induced shape selectivity for Suzuki C-C coupling reaction catalyzed by Pd particles in mesoporous silica. It is found that both aggregation ability and aggregating pattern of the reactants play the decisive role in controlling the shape selectivity, which are in turn determined by the balance between the hydrophobicity and hydrophilicity of the reactants, or in other words, by the balance between the noncovalent hydrogen bonding interaction and van der Waals forces. A general rule that allows prediction of the shape selectivity of a reactant has been proposed and verified against experiments. We show that molecular modeling is a powerful tool for rational design of new mesoporous systems and for the control of catalytic reactions that are important for the petrochemical industry.

  • 7.
    Aktekin, Burak
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Strukturkemi.
    Lacey, Matthew J.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Strukturkemi.
    Nordh, Tim
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Strukturkemi.
    Younesi, Reza
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Strukturkemi.
    Tengstedt, Carl
    Scania CV AB, SE-15187 Sodertalje, Sweden.
    Zipprich, Wolfgang
    Volkswagen AG, D-38436 Wolfsburg, Germany.
    Brandell, Daniel
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Strukturkemi.
    Edström, Kristina
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Strukturkemi.
    Understanding the Capacity Loss in LiNi0.5Mn1.5O4-Li4Ti5O12 Lithium-Ion Cells at Ambient and Elevated Temperatures2018Inngår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 122, nr 21, s. 11234-11248Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The high-voltage spinel LiNi0.5Mn1.5O4, (LNMO) is an attractive positive electrode because of its operating voltage around 4.7 V (vs Li/Li+) and high power capability. However, problems including electrolyte decomposition at high voltage and transition metal dissolution, especially at elevated temperatures, have limited its potential use in practical full cells. In this paper, a fundamental study for LNMO parallel to Li4Ti5O12 (LTO) full cells has been performed to understand the effect of different capacity fading mechanisms contributing to overall cell failure. Electrochemical characterization of cells in different configurations (regular full cells, back-to-back pseudo-full cells, and 3-electrode full cells) combined with an intermittent current interruption technique have been performed. Capacity fade in the full cell configuration was mainly due to progressively limited lithiation of electrodes caused by a more severe degree of parasitic reactions at the LTO electrode, while the contributions from active mass loss from LNMO or increases in internal cell resistance were minor. A comparison of cell formats constructed with and without the possibility of cross-talk indicates that the parasitic reactions on LTO occur because of the transfer of reaction products from the LNMO side. The efficiency of LTO is more sensitive to temperature, causing a dramatic increase in the fading rate at 55 degrees C. These observations show how important the electrode interactions (cross-talk) can be for the overall cell behavior. Additionally, internal resistance measurements showed that the positive electrode was mainly responsible for the increase of resistance over cycling, especially at 55 degrees C. Surface characterization showed that LNMO surface layers were relatively thin when compared with the solid electrolyte interphase (SEI) on LTO. The SEI on LTO does not contribute significantly to overall internal resistance even though these films are relatively thick. X-ray absorption near-edge spectroscopy measurements showed that the Mn and Ni observed on the anode were not in the metallic state; the presence of elemental metals in the SEI is therefore not implicated in the observed fading mechanism through a simple reduction process of migrated metal cations.

  • 8. Alarcon, Hugo
    et al.
    Hedlund, Maria
    Johansson, Erik M. J.
    Rensmo, Hakan
    Hagfeldt, Anders
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi.
    Boschloo, Gerrit
    KTH, Skolan för kemivetenskap (CHE), Kemi, Fysikalisk kemi.
    Modification of nanostructured TiO2 electrodes by electrochemical Al3+ insertion: Effects on dye-sensitized solar cell performance2007Inngår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 111, nr 35, s. 13267-13274Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Nanostructured TiO2 films were modified by insertion with aluminum ions using an electrochemical process. After heat treatment these films were found suitable as electrodes in dye-sensitized solar cells. By means of a catechol adsorption test, as well as photoelectron spectroscopy (PES), it was demonstrated that the density of Ti atoms at the metal oxide/electrolyte interface is reduced after Al modification. There is, however, not a complete coverage of aluminum oxide onto the TiO2, but the results rather suggest either the formation of a mixed Al-Ti oxide surface layer or formation of a partial aluminum oxide coating. No new phase could, however, be detected. In solar cells incorporating Al-modified TiO2 electrodes, both electron lifetimes and electron transport times were increased. At high concentrations of inserted aluminum ions, the quantum efficiency for electron injection was significantly decreased. Results are discussed at the hand of different models: A multiple trapping model, which can explain slower kinetics by the creation of additional traps during Al insertion, and a surface layer model, which can explain the reduced recombination rate, as well as the reduced injection efficiency, by the formation of a blocking layer.

  • 9. Alarcón, H.
    et al.
    Hedlund, Maria
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Fysiska institutionen, Fysik I.
    Johansson, Erik M. J.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Fysiska institutionen, Fysik I.
    Rensmo, Håkan
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Fysiska institutionen, Fysik I.
    Hagfeldt, Anders
    KTH, Fysikalisk kemi / Physical Chemistry.
    Boschloo, Gerrit K.
    KTH, Fysikalisk kemi / Physical Chemistry.
    Modification of nanostructured TiO2 electrodes by electrochemical Al3+ insertion: Effects on dye-sensitized solar cell performance2007Inngår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 111, nr 35, s. 13267-13274Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Nanostructured TiO2 films were modified by insertion with aluminum ions using an electrochemical process. After heat treatment these films were found suitable as electrodes in dye-sensitized solar cells. By means of a catechol adsorption test, as well as photoelectron spectroscopy (PES), it was demonstrated that the density of Ti atoms at the metal oxide/electrolyte interface is reduced after Al modification. There is, however, not a complete coverage of aluminum oxide onto the TiO2, but the results rather suggest either the formation of a mixed Al−Ti oxide surface layer or formation of a partial aluminum oxide coating. No new phase could, however, be detected. In solar cells incorporating Al-modified TiO2 electrodes, both electron lifetimes and electron transport times were increased. At high concentrations of inserted aluminum ions, the quantum efficiency for electron injection was significantly decreased. Results are discussed at the hand of different models:  A multiple trapping model, which can explain slower kinetics by the creation of additional traps during Al insertion, and a surface layer model, which can explain the reduced recombination rate, as well as the reduced injection efficiency, by the formation of a blocking layer.

  • 10.
    Ali, Ehesan
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och materialvetenskap.
    Sanyal, Biplab
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och materialvetenskap.
    Oppeneer, Peter M.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och materialvetenskap.
    Tuning the Magnetic Interaction between Manganese Porphyrins and Ferromagnetic Co Substrate through Dedicated Control of the Adsorption2009Inngår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 113, nr 32, s. 14381-14383Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We report, on the basis of density-functional theory+U (DFT+U) calculations that metalloporphyrins can adsorb on ferromagnetic metal surfaces in two distinct configurations. Two separate adsorption minima are obtained for manganese porphyrin (MnP) on Co from our DFT+U total energy calculations, which correspond to strong and weak adsorption strengths, respectively. By steering the nature of adsorption, we find that distinct chemical interactions as well as magnetic exchange interactions between the metalloporphyrin and the metal surface can be realized. We furthermore show that a switching of the MnP molecule's spin state can occur even for the weakly adsorbed case. This new discovery opens up prospects for engineering the chemical and magnetic exchange interaction in new functionalized spintronic materials.

  • 11. Al-Shammari, Rusul M.
    et al.
    Manzo, Michele
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik.
    Gallo, Katia
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Kvantelektronik och -optik, QEO.
    Rice, James H.
    Rodriguez, Brian J.
    Tunable Wettability of Ferroelectric Lithium Niobate Surfaces: The Role of Engineered Microstructure and Tailored Metallic Nanostructures2017Inngår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 121, nr 12, s. 6643-6649Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    An important aspect of optimizing micro- and optofluidic devices for lab on -a-chip systems is the ability to engineer materials properties including surface structure and charge to control wettability. Biocompatible ferroelectric lithium niobate (LN), which is well-known for acoustic and nonlinear optical applications, has recently found potential micro- and optofluidic applications. However, the tunable wettability of such substrates has yet to be explored in detail. Here, we show that the contact angle of LN substrates can be reproducibly tailored between similar to 7 degrees and similar to 421 degrees by controlling the surface topography and chemistry at the nano- and micrometer scale via ferroelectric domain and polarization engineering and polarization-directed photoassisted deposition of metallic nanostructures.

  • 12. Amft, M.
    et al.
    Walle, L. E.
    Ragazzon, Davide
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Molekyl- och kondenserade materiens fysik.
    Borg, A.
    Uvdal, P.
    Skorodumova, Natalia V.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Materialteori.
    Sandell, Anders
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Molekyl- och kondenserade materiens fysik.
    A Molecular Mechanism for the Water-Hydroxyl Balance during Wetting of TiO22013Inngår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 117, nr 33, s. 17078-17083Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We show that the formation of the wetting layer and the experimentally observed continuous shift of the H2O-OH balance toward molecular water at increasing coverage on a TiO2(110) surface can be rationalized on a molecular level. The mechanism is based on the initial formation of stable hydroxyl pairs, a repulsive interaction between these pairs, and an attractive interaction with respect to water molecules. The experimental data are obtained by synchrotron radiation photoelectron spectroscopy and interpreted with the aid of density functional theory calculations and Monte Carlo simulations.

  • 13.
    Amft, Martin
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Flerskalig materialmodellering.
    Walle, L. E.
    Ragazzon, D.
    Borg, A.
    Uvdal, P.
    Skorodumova, Natalia V.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Flerskalig materialmodellering.
    Sandell, A.
    A Molecular Mechanism for the Water-Hydroxyl Balance during Wetting of TiO22013Inngår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 117, nr 33, s. 17078-17083Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We show that the formation of the wetting layer and the experimentally observed continuous shift of the H2O-OH balance toward molecular water at increasing coverage on a TiO2(110) surface can be rationalized on a molecular level. The mechanism is based on the initial formation of stable hydroxyl pairs, a repulsive interaction between these pairs, and an attractive interaction with respect to water molecules. The experimental data are obtained by synchrotron radiation photoelectron spectroscopy and interpreted with the aid of density functional theory calculations and Monte Carlo simulations.

  • 14.
    Amorim, Rodrigo G.
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Materialteori. Univ Fed Fluminense, Dept Fis, ICEx, Volta Redonda, RJ, Brazil..
    Rocha, Alexandre R.
    Univ Estadual Paulista, UNESP, Inst Fis Teor, Sao Paulo, Brazil..
    Scheicher, Ralph H.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Materialteori.
    Boosting DNA Recognition Sensitivity of Graphene Nanogaps through Nitrogen Edge Functionalization2016Inngår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 120, nr 34, s. 19384-19388Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    One of the challenges for next generation DNA sequencing is to have a robust, stable, and reproducible nanodevice. In this work, we propose how to improve the sensing of DNA nucleobase using functionalized graphene nanogap as a solid state device. Two types of edge functionalization, namely, either hydrogen or nitrogen, were considered. We showed that, independent of species involved in the edge passivation, the highest-to-lowest order of the nucleobase transmissions is not altered, but the intensity is affected by several orders of magnitude. Our results show that nitrogen edge tends to p-dope graphene, and most importantly, it contributes with resonance states close to the Fermi level, which can be associated with the increased conductance. Finally, the translocation process of nucleobases passing through the nanogap was also investigated by varying their position from a certain height (from +3 to -3 angstrom) with respect to the graphene sheet to show that nitrogen-terminated sheets have enhanced sensitivity, as moving the nucleobase by approximately 1 angstrom reduces the conductance by up to 3 orders of magnitude.

  • 15.
    Andersson, Klas J.
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. SLAC National Accelerator Laboratory, USA.
    Ogasawara, Hirohito
    Nordlund, Dennis
    Brown, Gordon E., Jr.
    Nilsson, Anders
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. SLAC National Accelerator Laboratory, USA.
    Preparation, Structure, and Orientation of Pyrite FeS2{100} Surfaces: Anisotropy, Sulfur Monomers, Dimer Vacancies, and a Possible FeS Surface Phase2014Inngår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 118, nr 38, s. 21896-21903Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Sulfur dimer (S-2(2-)) terminated pyrite FeS2{100} surfaces with a low energy electron diffraction (LEED) pattern of 2 x 1 symmetry are reported. The 2 X 1 symmetry correlates with the orientation of the anisotropic surface structure and external symmetry of macroscopic striations on the pyrite cube face. The basic condition to form these surfaces is a mild 200 V Ne+ sputter-cleaning procedure followed by a 570 K anneal of the sample in a 10(-7) Ton S-2(g) atmosphere. Controlled amounts of surface sulfur monomers (S2-) can be introduced by mild sputtering of the sulfur dimer terminated surfaces. At low monomer concentrations the surface displays the same characteristic 1 x 1 LEED pattern as that for fracture-generated surfaces. With increasing sulfur depletion, a (1/ root 2 x 1/ root 2)R45 degrees LEED pattern emerges, and soft X-ray photoelectron spectroscopy (XPS) results show a sulfur dinner deficient near-surface region and a new high binding energy sulfur spectral component suggesting the presence of local coordination environments where sulfur monomers are coordinated by four Fe ions compared to three as in the pyrite structure. The plausible formation of a defective FeS-like surface phase where monomeric sulfurs are coordinated by four Fe ions, and bond counting energetics favoring surface sulfur monomer recombination around Fe vacancy sites on pyrite FeS2{100}, both imply surface sulfur dimer vacancy sites with unique adsorption and reactivity properties. Taken together, our results suggest a very rich and dynamic defect structural landscape at pyrite FeS2{100} surfaces with direct implications for its surface chemical activity.

  • 16.
    Andersson, M.
    et al.
    Chalmers University of Technology.
    Kiselev, A.
    Umeå University.
    Österlund, Lars
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets fysik.
    Palmqvist, A E C
    Chalmers University of Technology.
    Microemulsion-mediated room-temperature synthesis of high-surface-area rutile and its photocatalytic performance2007Inngår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 111, nr 18, s. 6789-6797Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Nanosized titania having the rutile crystalline structure was synthesized at room temperature using a microemulsion-mediated system. The formed rutile particles had a diameter of 3 nm, which corresponds well with the droplet size of the water-in-oil microemulsion used for their preparation. The crystallinity was monitored by both X-ray diffraction (XRD) and electron diffraction, together with dark-field electron microscopy (TEM) and high-resolution TEM. The rutile had a high specific surface area (similar to 300 m(2)/g) according to N-2 adsorption and the BET equation. To our knowledge, this is the highest specific surface area ever reported for rutile. The rutile crystals aligned in a specific crystallographic direction forming elongated aggregates 200-1000 nm in size, as observed by TEM and high-resolution TEM. The titania formation was followed in situ using dynamic light scattering and UV-vis spectroscopy, and together with TEM and XRD performed on samples collected throughout the duration of the titania synthesis, the results gave support for a formation scheme involving the initial formation of amorphous titania followed by crystallization of rutile. The photocatalytic performance of the formed material was evaluated by in situ Fourier transform infrared spectroscopy and compared to that of a rutile sample having a lower specific surface area (similar to 40 m(2)/g). The TEM and formate adsorption experiments revealed that the high-surface-area rutile had a much higher fraction of (101) facets than the low-surface-area sample, which predominantly exposed (110) facets. In particular, a new bidentate formate (mu-formate) species bridge-bonded to the (101) facet could be identified with characteristic bands at 1547 and 1387 cm(-1). The photodegradation rate of this species was found to be similar to the mu-formate species on the (110) facet. However, the overall formate degradation rate was larger on the high-surface-area rutile sample because of a high concentration of the more readily photodegradable monodentate formate (eta(1)-formate) on that sample.

  • 17.
    Andrén, Daniel
    et al.
    Department of Physics, Chalmers University of Technology, Göteborg, Sweden.
    Länk, Nils Odebo
    Department of Physics, Chalmers University of Technology, Göteborg, Sweden.
    Sípová-Jungová, Hana
    Department of Physics, Chalmers University of Technology, Göteborg, Sweden.
    Jones, Steven
    Department of Physics, Chalmers University of Technology, Göteborg, Sweden.
    Johansson, Peter
    Örebro universitet, Institutionen för naturvetenskap och teknik. Department of Physics, Chalmers University of Technology, Göteborg, Sweden.
    Käll, Mikael
    Department of Physics, Chalmers University of Technology, Göteborg, Sweden.
    Surface Interactions of Gold Nanoparticles Optically Trapped against an Interface2019Inngår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 123, nr 26, s. 16406-16414Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Particles that diffuse in close proximity to a surface are expected to behave differently than in free solution because the surface interaction will influence a number of physical properties, including the hydrodynamic, optical, and thermal characteristics of the particle. Understanding the influence of such effects is particularly important in view of the increasing interest in laser tweezing of colloidal resonant nanoparticles for applications such as nanomotors and optical printing and for investigations of unconventional optical forces. Therefore, we used total internal reflection microscopy to probe the interaction between a glass surface and individual similar to 100 nm gold nanoparticles trapped by laser tweezers. The results show that particles can be optically confined at controllable distances ranging between similar to 30 and similar to 90 nm from the surface, depending on the radiation pressure of the trapping laser and the ionic screening of the surrounding liquid. Moreover, the full particle-surface distance probability distribution can be obtained for single nanoparticles by analyzing temporal signal fluctuations. The experimental results are in excellent agreement with Brownian dynamics simulations that take the full force field and photothermal heating into account. At the observed particle-surface distances, translational friction coefficients increase by up to 60% compared to freely diffusing particles, whereas the rotational friction and thermal dissipation are much less affected. The methodology used here is general and can be adapted to a range of single nanoparticle-surface interaction investigations.

  • 18. Araujo, Rafael B.
    et al.
    Banerjee, Amitava
    Ahujati, Rajeev
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad materialfysik. Uppsala University, Sweden.
    Divulging the Hidden Capacity and Sodiation Kinetics of NaxC6Cl4O2: A High Voltage Organic Cathode for Sodium Rechargeable Batteries2017Inngår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 121, nr 26, s. 14027-14036Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In the current emerging sustainable organic battery field, quinones are seen as one of the prime candidates for application in rechargeable battery electrodes. Recently, C6Cl4O2, a modified quinone, has been proposed as a high voltage organic cathode. However, the sodium insertion mechanism behind the cell reaction remained unclear due to the nescience of the right crystal structure. Here, the framework of the density functional theory (DFT) together with an evolutionary algorithm was employed to elucidate the crystal structures of the compounds NaxC6Cl4O2 (x = 0.5, 1.0, 1.5 and 2). Along with the usefulness of PBE functional to reflect the experimental potential, also the importance of the hybrid functional to divulge the hidden theoretical capacity is evaluated. We showed that the experimentally observed lower specific capacity is a result of the great stabilization of the intermediate phase Na1.5C6Cl4O2. The calculated activation barriers for the ionic hops, are 0.68, 0.40, and 0.31 eV, respectively, for NaC6Cl4O2, Na1.5C6Cl4O2, and Na2C6Cl4O2. These results indicate that the kinetic process must not be a limiting factor upon Na insertion. Finally, the correct prediction of the specific capacity has confirmed that the theoretical strategy used, employing evolutionary simulations together with the hybrid functional framework, can rightly model the thermodynamic process in organic electrode compounds.

  • 19.
    Araujo, Rafael Barros Neves de Araujo
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi.
    Banerjee, Amitava
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi.
    Ahuja, Rajeev
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi.
    Divulging the Hidden Capacity and Sodiation Kinetics of NaxC6Cl4O2 : A High Voltage Organic2017Inngår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455Artikkel i tidsskrift (Annet vitenskapelig)
  • 20.
    Araujo, Rafael Barros Neves de
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Materialteori.
    Banerjee, Amitava
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Materialteori.
    Ahuja, Rajeev
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Materialteori. Royal Inst Technol KTH, Dept Mat & Engn, Appl Mat Phys, S-10044 Stockholm, Sweden..
    Divulging the Hidden Capacity and Sodiation Kinetics of NaxC6Cl4O2: A High Voltage Organic Cathode for Sodium Rechargeable Batteries2017Inngår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 121, nr 26, s. 14027-14036Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In the current emerging sustainable organic battery field, quinones are seen as one of the prime candidates for application in rechargeable battery electrodes. Recently, C6Cl4O2, a modified quinone, has been proposed as a high voltage organic cathode. However, the sodium insertion mechanism behind the cell reaction remained unclear due to the nescience of the right crystal structure. Here, the framework of the density functional theory (DFT) together with an evolutionary algorithm was employed to elucidate the crystal structures of the compounds NaxC6Cl4O2 (x = 0.5, 1.0, 1.5 and 2). Along with the usefulness of PBE functional to reflect the experimental potential, also the importance of the hybrid functional to divulge the hidden theoretical capacity is evaluated. We showed that the experimentally observed lower specific capacity is a result of the great stabilization of the intermediate phase Na1.5C6Cl4O2. The calculated activation barriers for the ionic hops are 0.68, 0.40, and 0.31 eV, respectively, for NaC6Cl4O2, Na1.5C6Cl4O2, and Na2C6Cl4O2. These results indicate that the kinetic process must not be a limiting factor upon Na insertion. Finally, the correct prediction of the specific capacity has confirmed that the theoretical strategy used, employing evolutionary simulations together with the hybrid functional framework, can rightly model the thermodynamic process in organic electrode compounds.

  • 21.
    Arruda, Lucas M.
    et al.
    Free Univ Berlin, Inst Expt Phys, Arnimallee 14, D-14195 Berlin, Germany;Minist Educ Brazil, CAPES Fdn, BR-70040020 Brasilia, DF, Brazil.
    Ali, Md. Ehesan
    Inst Nano Sci & Technol, Phase 10,Sect 64, Mohali 160062, Punjab, India.
    Bernien, Matthias
    Free Univ Berlin, Inst Expt Phys, Arnimallee 14, D-14195 Berlin, Germany.
    Nickel, Fabian
    Free Univ Berlin, Inst Expt Phys, Arnimallee 14, D-14195 Berlin, Germany.
    Kopprasch, Jens
    Free Univ Berlin, Inst Expt Phys, Arnimallee 14, D-14195 Berlin, Germany.
    Czekelius, Constantin
    Heinrich Heine Univ Dusseldorf, Inst Organ Chem & Makromol Chem, Univ Str 1, D-40225 Dusseldorf, Germany.
    Oppeneer, Peter M.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Materialteori.
    Kuch, Wolfgang
    Free Univ Berlin, Inst Expt Phys, Arnimallee 14, D-14195 Berlin, Germany.
    Modifying the Magnetic Anisotropy of an Iron Porphyrin Molecule by an on-Surface Ring-Closure Reaction2019Inngår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 123, nr 23, s. 14547-14555Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The magnetic properties of adsorbed metalloporphyrin molecules can be altered or tuned by the substrate, additional axial ligands, or changes to the molecules' macrocycle. These modifications influence the electronic configuration of the fourfold-coordinated central metal ion that is responsible for the metalloporphyrins' magnetic properties. We report a substantial increase in the effective spin moment obtained from sum-rule analysis of X-ray magnetic circular dichroism for an iron metalloporphyrin molecule on Au(111) through its conversion from iron(II)-octaethylporphyrin to iron(II)-tetrabenzoporphyrin in a surface-assisted ring-closure ligand reaction. Density functional theory calculations with additional strong Coulomb correlation (DFT+U) show that the on-surface reaction alters the conformation of the molecule, increasing its planarity and the ion-surface distance. A spin-Hamiltonian fit of the magnetization as a function of field reveals a substantial increase in the intra-atomic magnetic dipole term (T-z) and a decrease in the magnitude of the easy-plane anisotropy upon ring closure. This consequence of the ring closure demonstrates how new magnetic properties can be obtained from on-surface reactions, resulting here in significant modifications to the magnetic anisotropy of the Fe ion, and sheds light onto the molecule-substrate interaction in these systems.

  • 22. Asano, Kohta
    et al.
    Westerwaal, Ruud J.
    Anastasopol, Anca
    Mooij, Lennard P. A.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Materialfysik.
    Boelsma, Christiaan
    Ngene, Peter
    Schreuders, Herman
    Eijt, Stephan W. H.
    Dam, Bernard
    Destabilization of Mg Hydride by Self-Organized Nanoclusters in the Immiscible Mg-Ti System2015Inngår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 119, nr 22, s. 12157-12164Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Mg is an attractive hydrogen storage material not only because of its high gravimetric and volumetric hydrogen capacities but also because of it low material costs. However, the hydride of MgH2 is too stable to release hydrogen under moderate conditions. We demonstrate that the formation of nanometer-sized clusters of Mg reduces the stability of MgH2 by the interface energy effect in the immiscible Mg-Ti system. Ti-rich MgxTi1-x (x < 0.5) thin films deposited by magnetron sputtering have a hexagonal close packed (HCP) structure, which forms a face-centered cubic (FCC) hydride phase upon hydrogenation. Positron Doppler broadening depth profiling demonstrates that after hydrogenation, nanometer-sized MgH2 clusters are formed which are coherently embedded in an FCC TiH2 matrix. The P (pressure)-T (optical transmission) isotherms measured by hydrogenography show that these MgH2 clusters are destabilized. This indicates that the formation of nanometer-sized Mg allows for the development of a lightweight and cheap hydrogen storage material with a lower desorption temperature.

  • 23.
    Bakulin, Artem A.
    et al.
    FOM Institute AMOLF, Netherlands; University of Cambridge, England.
    Xia, Yuxin
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska fakulteten.
    Bakker, Huib J.
    FOM Institute AMOLF, Netherlands.
    Inganäs, Olle
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska fakulteten.
    Gao, Feng
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska fakulteten.
    Morphology, Temperature, and Field Dependence Separation in High-Efficiency Solar Cells Based on Polyquinoxaline Copolymer2016Inngår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 120, nr 8, s. 4219-4226Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Charge separation and recombination are key processes determining the performance of organic optoelectronic devices. Here we combine photoluminescence and photovoltaic characterization of organic solar cell devices with ultrafast multipulse photocurrent spectroscopy to investigate charge generation mechanisms in the organic photovoltaic devices based on a blend of an alternating polyquinoxaline copolymer with fullerene. The combined use of these techniques enables the determination of the contributions of geminate and bimolecular processes to the solar cell performance. We observe that charge separation is not a temperature-activated process in the studied materials. At the same time, the generation of free charges shows a dear external field and morphology dependence. This indicates that the critical step of charge separation involves the nonequilibrium state that is formed at early times after photoexcitation, when the polaronic localization is not yet complete. This work reveals new aspects of molecular level charge dynamics in the organic light-conversion systems.

  • 24. Banerjee, R.
    et al.
    Novak, J.
    Frank, C.
    Girleanu, M.
    Ersen, O.
    Brinkmann, M.
    Anger, F.
    Lorch, C.
    Dieterle, J.
    Gerlach, A.
    Drnec, J.
    Yu, Shun
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Polymera material. Deutsches Elektronen-Synchrotron (DESY), Hamburg, Germany .
    Schreiber, F.
    Structure and Morphology of Organic Semiconductor-Nanoparticle Hybrids Prepared by Soft Deposition2015Inngår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 119, nr 9, s. 5225-5237Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We present an extensive structural analysis of hybrid architectures prepared by the soft incorporation of gold nanoparticles (AuNPs) within an organic semiconductor matrix of diindenoperylene (DIP). Such soft or noninvasive deposition of nanoparticles within organic semiconducting host matrices not only minimizes the influence of the deposition process on the order and properties of the organic host molecules, but also offers additional control in the process of incorporation. The hybrid structures were characterized by X-ray scattering techniques including grazing incidence small angle X-ray scattering (GISAXS), grazing incidence X-ray diffraction (GIXD), X-ray reflectivity (XRR), and complemented by atomic force microscopy (AFM), photoluminescence (PL) spectroscopy, and transmission electron microscopy (TEM) measurements. We show that different strategies of incorporating the nanoparticles in the host matrix lead to drastically different structure and morphologies. Particularly remarkable is the morphological change observed in the matrix of DIP as well as the AuNPs due to the influence of organic solvents, as evidenced by TEM tomography measurements, which revealed the exact location of the AuNPs within the organic host. It is also demonstrated that AuNPs can be successfully used as tunable templates for the growth of the organic semiconductors with desired island sizes and distances.

  • 25.
    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 correction2012Inngår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, s. 9487-9497Artikkel i tidsskrift (Fagfellevurdert)
    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

  • 26.
    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 bonding2013Inngår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 117, nr 45, s. 23887-23898Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 27.
    Barcaro, Giovanni
    et al.
    CNR, IPCF, Inst Chem & Phys Proc, Via G Moruzzi 1, I-56124 Pisa, Italy.
    Sernenta, Luca
    CNR, IPCF, Inst Chem & Phys Proc, Via G Moruzzi 1, I-56124 Pisa, Italy.
    Monti, Susanna
    CNR, ICCOM, Inst Chem Organometall Cpds, Via G Moruzzi 1, I-56124 Pisa, Italy.
    Carravetta, Vincenzo
    CNR, IPCF, Inst Chem & Phys Proc, Via G Moruzzi 1, I-56124 Pisa, Italy.
    Broqvist, Peter
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Strukturkemi.
    Kullgren, Jolla
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Strukturkemi.
    Hermansson, Kersti
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Strukturkemi.
    Dynamical and Structural Characterization of the Adsorption of Fluorinated Alkane Chains onto CeO22018Inngår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 122, nr 41, s. 23405-23413Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The widespread use of ceria-based materials and the need to design suitable strategies to prepare eco-friendly CeO2 supports for effective catalytic screening induced us to extend our computational multiscale protocol to the modeling of the hybrid organic/oxide interface between prototypical fluorinated linear alkane chains (polyethylene-like oligomers) and low-index ceria surfaces. The combination of quantum chemistry calculations and classical reactive molecular dynamics simulations provides a comprehensive picture of the interface and discloses, at the atomic level, the main causes of typical adsorption modes. The data show that at room temperature. a moderate. percentage` of fluorine atoms (around 25%) can enhance the interaction of the organic chains by anchoring strongly pivotal fluorines to the channels of the underneath ceria (100) surface, whereas an excessive content can remarkably reduce this interaction because of the repulsion between fluorine and the negatively charged oxygen of the surface.

  • 28. Bareno, Javier
    et al.
    Shkrob, Ilya A.
    Gilbert, James A.
    Klett, Matilda
    Abraham, Daniel P.
    Capacity Fade and Its Mitigation in Li-Ion Cells with Silicon-Graphite Electrodes2017Inngår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 121, nr 38, s. 20640-20649Artikkel i tidsskrift (Fagfellevurdert)
  • 29. Barrabes, Noelia
    et al.
    Foettinger, Karin
    Llorca, Jordi
    Dalinov, Anton
    Medina, Francesc
    Sa, Jacinto
    Hardacre, Christopher
    Rupprechter, Guenther
    Pretreatment Effect on Pt/CeO2 Catalyst in the Selective Hydrodechlorination of Trichloroethylene2010Inngår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 114, nr 41, s. 17675-17682Artikkel i tidsskrift (Fagfellevurdert)
  • 30. Barzegar, Hamid R.
    et al.
    Nitze, Florian
    Sharifi, Tiva
    Ramstedt, Madeleine
    Tai, Cheuk W.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Malolepszy, Artur
    Stobinski, Leszek
    Wagberg, Thomas
    Simple Dip-Coating Process for the Synthesis of Small Diameter Single-Walled Carbon Nanotubes-Effect of Catalyst Composition and Catalyst Particle Size on Chirality and Diameter2012Inngår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 116, nr 22, s. 12232-12239Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We report on a dip-coating method to prepare catalyst particles (mixture of iron and cobalt) with a controlled diameter distribution on silicon wafer substrates by changing the solution's concentration and withdrawal velocity. The size and distribution of the prepared catalyst particles were analyzed by atomic force microscopy. Carbon nanotubes were grown by chemical vapor deposition on the substrates with the prepared catalyst particles. By decreasing the catalyst particle size to below 10 nm, the growth of carbon nanotubes can be tuned from few-walled carbon nanotubes, with homogeneous diameter, to highly pure single-walled carbon nanotubes. Analysis of the Raman radial breathing modes, using three different Raman excitation wavelengths (488, 633, and 785 nm), showed a relatively broad diameter distribution (0.8-1.4 nm) of single-walled carbon nanotubes with different chiralities. However, by changing the composition of the catalyst particles while maintaining the growth parameters, the chiralities of single-walled carbon nanotubes were reduced to mainly four different types, (12, 1), (12, 0), (8, 5), and (7, 5), accounting for about 70% of all nanotubes.

  • 31.
    Barzegar, Hamid R.
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Nitze, Florian
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Sharifi, Tiva
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Ramstedt, Madeleine
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Tai, Cheuk W.
    Malolepszy, Artur
    Stobinski, Leszek
    Wågberg, Thomas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Simple Dip-Coating Process for the Synthesis of Small Diameter Single-Walled Carbon Nanotubes-Effect of Catalyst Composition and Catalyst Particle Size on Chirality and Diameter2012Inngår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 116, nr 22, s. 12232-12239Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We report on a dip-coating method to prepare catalyst particles (mixture of iron and cobalt) with a controlled diameter distribution on silicon wafer substrates by changing the solution's concentration and withdrawal velocity. The size and distribution of the prepared catalyst particles were analyzed by atomic force microscopy. Carbon nanotubes were grown by chemical vapor deposition on the substrates with the prepared catalyst particles. By decreasing the catalyst particle size to below 10 nm, the growth of carbon nanotubes can be tuned from few-walled carbon nanotubes, with homogeneous diameter, to highly pure single-walled carbon nanotubes. Analysis of the Raman radial breathing modes, using three different Raman excitation wavelengths (488, 633, and 785 nm), showed a relatively broad diameter distribution (0.8-1.4 nm) of single-walled carbon nanotubes with different chiralities. However, by changing the composition of the catalyst particles while maintaining the growth parameters, the chiralities of single-walled carbon nanotubes were reduced to mainly four different types, (12, 1), (12, 0), (8, 5), and (7, 5), accounting for about 70% of all nanotubes.

  • 32.
    Barzegar, Hamid Reza
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Gracia-Espino, Eduardo
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Sharifi, Tiva
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Nitze, Florian
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Wågberg, Thomas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Nitrogen Doping Mechanism in Small Diameter Single-Walled Carbon Nanotubes: Impact on Electronic Properties and Growth Selectivity2013Inngår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 117, nr 48, s. 25805-25816Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Nitrogen doping in carbon nanostructures has attracted interest for more than a decade, and recent implementation of such structures in energy conversion systems has boosted the interest even more. Despite numerous studies, the structural conformation and stability of nitrogen functionalities in small diameter single-walled carbon nanotubes (SWNTs), and the impact of these functionalities on the electronic and mechanical properties of the SWNTs, are incomplete. Here we report a detailed study on nitrogen doping in SWNTs with diameters in the range of 0.8?1.0 nm, with well-defined chirality. We show that the introduction of nitrogen in the carbon framework significantly alters the stability of certain tubes, opening for the possibility to selectively grow nitrogen-doped SWNTs with certain chirality and diameter. At low nitrogen concentration, pyridinic functionalities are readily incorporated and the tubular structure is well pertained. At higher concentrations, pyrrolic functionalities are formed, which leads to significant structural deformation of the nanotubes and hence a stop in growth of crystalline SWNTs. Raman spectroscopy is an important tool to understand guest atom doping and electronic charge transfer in SWNTs. By correlating the influence of defined nitrogen functionalities on the electronic properties of SWNTs with different chirality, we make precise interpretation of experimental Raman data. We show that the previous interpretation of the double-resonance G?-peak in many aspects is wrong and instead can be well-correlated to the type of nitrogen doping of SWNTs originating from the p- or n-doping nature of the nitrogen incorporation. Our results are supported by experimental and theoretical data.

  • 33.
    Batista dos Santos, Renato
    et al.
    Institute Federal Baiano, Brazil.
    de Brito Mota, Fernando
    University of Federal Bahia, Brazil.
    Rivelino, Roberto
    University of Federal Bahia, Brazil.
    Gueorguiev, Gueorgui Kostov
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten.
    Electric-Field Control of Spin-Polarization and Semiconductor-to-Metal Transition in Carbon-Atom-Chain Devices2017Inngår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 121, nr 46, s. 26125-26132Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We propose hybrid molecular systems containing small carbon atomic chains interconnected by graphene-like flakes, theoretically predicted as true energy minima, as low-dimensional structures that may be useful in electronic devices at the limit of the atomic miniaturization. The effects of an external electric field applied along the direction of the carbon chains indicate that it is possible to control energy gap and spin polarization with sufficiently high strength, within the limit of the structural restoring of the systems. In this sense, by applying electric fields with magnitudes in the 1-5 V/nm range, we obtain semiconductor-to-metallic transitions for all odd-numbered carbon-chain systems proposed here. Furthermore, high-spin-to-low-spin transitions are determined for these systems as a function of the electric-field magnitude. In the case of the even-numbered carbon-chain systems, the overall electric field effect is pushing electron density near the Fermi level, leading to a gapless or metallic regime at 3.0 V/nm. An electric-field control of the spin-polarization of these latter systems is only achieved by doping the extremities of the graphene-like terminations with sulfur atoms. This finding, however, is beneficial for applications of these systems in spin controlled carbon-based devices connected by gold electrodes, even in the presence of a weak spin-orbit coupling.

  • 34.
    Bender, Philipp
    et al.
    Universidad de Cantabria, Spain.
    Fock, Jeppe
    DTU Technical University of Denmark, Denmark.
    Frandsen, Cathrine
    DTU Technical University of Denmark, Denmark.
    Hansen, Mikkel F.
    DTU Technical University of Denmark, Denmark.
    Balceris, Christoph
    TU Braunschweig, Germany.
    Ludwig, Frank
    TU Braunschweig, Germany.
    Posth, Oliver
    Physikalisch-Technische Bundesanstalt, Germany.
    Wetterskog, Erik
    Uppsala University, Sweden.
    Bogart, Lara K.
    University College London, UK.
    Southern, Paul
    University College London, UK.
    Szczerba, Wojciech
    Bundesanstalt für Materialforschung und -prüfung, Germany; AGH University of Science and Technology, Poland.
    Zeng, Lunjie
    Chalmers University of Technology, Sweden.
    Witte, Kerstin
    University of Rostock, Germany; Micromod Partikeltechnologie GmbH, Germany.
    Gruettner, Cordula
    Micromod Partikeltechnologie GmbH, Germany.
    Westphal, Fritz
    Micromod Partikeltechnologie GmbH, Germany.
    Honecker, Dirk
    Institut Laue-Langevin, France.
    Gonzalez-Alonso, David
    Universidad de Cantabria, Spain.
    Fernandez Barquin, Luis
    Universidad de Cantabria, Spain.
    Johansson, Christer
    RISE - Research Institutes of Sweden, ICT, Acreo.
    Relating Magnetic Properties and High Hyperthermia Performance of Iron Oxide Nanoflowers2018Inngår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 122, nr 5, s. 3068-3077Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We investigated, in depth, the interrelations among structure, magnetic properties, relaxation dynamics and magnetic hyperthermia performance of magnetic nanoflowers. The nanoflowers are about 39 nm in size, and consist of densely packed iron oxide cores. They display a remanent magnetization, which we explain by the exchange coupling between the cores, but we observe indications for internal spin disorder. By polarized small-angle neutron scattering, we unambiguously confirm that, on average, the nano flowers are preferentially magnetized along one direction. The extracted discrete relaxation time distribution of the colloidally dispersed particles indicates the presence of three distinct relaxation contributions. We can explain the two slower processes by Brownian and classical Neel relaxation, respectively. The additionally observed very fast relaxation contributions are attributed by us to the relaxation of disordered spins within the nanoflowers. Finally, we show that the intrinsic loss power (ILP, magnetic hyperthermia performance) of the nanoflowers measured in colloidal dispersion at high frequency is comparatively large and independent of the viscosity of the surrounding medium. This concurs with our assumption that the observed relaxation in the high frequency range is primarily a result of internal spin relaxation, and possibly connected to the disordered spins within the individual nanoflowers.

  • 35.
    Bender, Philipp
    et al.
    Univ Cantabria, E-39005 Santander, Spain..
    Fock, Jeppe
    Tech Univ Denmark, DK-2800 Lyngby, Denmark..
    Frandsen, Cathrine
    Tech Univ Denmark, DK-2800 Lyngby, Denmark..
    Hansen, Mikkel F.
    Tech Univ Denmark, DK-2800 Lyngby, Denmark..
    Balceris, Christoph
    TU Braunschweig, D-38106 Braunschweig, Germany..
    Ludwig, Frank
    TU Braunschweig, D-38106 Braunschweig, Germany..
    Posth, Oliver
    Phys Tech Bundesanstalt, D-10587 Berlin, Germany..
    Wetterskog, Erik
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets fysik.
    Bogart, Lara K.
    UCL, London W1S 4BS, England..
    Southern, Paul
    UCL, London W1S 4BS, England..
    Szczerba, Wojciech
    Bundesanstalt Mat Forsch & Prufung, D-12205 Berlin, Germany.;AGH Univ Sci & Technol, PL-30059 Krakow, Poland..
    Zeng, Lunjie
    Chalmers Univ Technol, S-41296 Gothenburg, Sweden..
    Witte, Kerstin
    Univ Rostock, D-18059 Rostock, Germany.;Micromod Partikeltechnol GmbH, D-18119 Rostock, Germany..
    Grüttner, Cordula
    Micromod Partikeltechnol GmbH, D-18119 Rostock, Germany..
    Westphal, Fritz
    Micromod Partikeltechnol GmbH, D-18119 Rostock, Germany..
    Honecker, Dirk
    Inst Laue Langevin, F-38042 Grenoble, France..
    Gonzalez-Alonso, David
    Univ Cantabria, E-39005 Santander, Spain..
    Fernandez Barquin, Luis
    Univ Cantabria, E-39005 Santander, Spain..
    Johansson, Christer
    RISE Acreo, S-40014 Gothenburg, Sweden..
    Relating Magnetic Properties and High Hyperthermia Performance of Iron Oxide Nanoflowers2018Inngår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 122, nr 5, s. 3068-3077Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We investigated, in depth, the interrelations among structure, magnetic properties, relaxation dynamics and magnetic hyperthermia performance of magnetic nanoflowers. The nanoflowers are about 39 nm in size, and consist of densely packed iron oxide cores. They display a remanent magnetization, which we explain by the exchange coupling between the cores, but we observe indications for internal spin disorder. By polarized small-angle neutron scattering, we unambiguously confirm that, on average, the nano flowers are preferentially magnetized along one direction. The extracted discrete relaxation time distribution of the colloidally dispersed particles indicates the presence of three distinct relaxation contributions. We can explain the two slower processes by Brownian and classical Neel relaxation, respectively. The additionally observed very fast relaxation contributions are attributed by us to the relaxation of disordered spins within the nanoflowers. Finally, we show that the intrinsic loss power (ILP, magnetic hyperthermia performance) of the nanoflowers measured in colloidal dispersion at high frequency is comparatively large and independent of the viscosity of the surrounding medium. This concurs with our assumption that the observed relaxation in the high frequency range is primarily a result of internal spin relaxation, and possibly connected to the disordered spins within the individual nanoflowers.

  • 36.
    Bhandary, Sumanta
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Materialteori.
    Penazzi, Gabriele
    Univ Bremen, BCCMS, D-28359 Bremen, Germany..
    Fransson, Jonas
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Materialteori.
    Frauenheim, Thomas
    Univ Bremen, BCCMS, D-28359 Bremen, Germany..
    Eriksson, Olle
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Materialteori.
    Sanyal, Biplab
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Materialteori.
    Controlling Electronic Structure and Transport Properties of Zigzag Graphene Nanoribbons by Edge Functionalization with Fluorine2015Inngår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 119, nr 36, s. 21227-21233Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this work, we report a detailed study of the electronic structure and transport properties of mono- and difluorinated edges of zigzag graphene nanoribbons (ZGNR) using density functional theory (DFT). The calculated formation energies at 0 K indicate that the stability of the nanoribbons increases with the increase in the concentration of difluorinated edge C atoms along with an interesting variation of the energy gaps between 0.0 to 0.66 eV depending on the concentration. This gives a possibility of tuning the band gaps by controlling the concentration of F for terminating the edges of the nanoribbons. The DFT results have been reproduced by density functional tight binding method. Using the nonequilibrium Green functional method, we have calculated the transmission coefficients of several mono- and difluorinated ZGNR as a function of unit cell size and degree of homogeneous disorder caused by the random placement of mono and difluorinated C atoms at the edges.

  • 37. Bidermane, I.
    et al.
    Luder, J.
    Ahmadi, Sareh
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Material- och nanofysik, Materialfysik, MF.
    Grazioli, C.
    Bouvet, M.
    Brena, B.
    Martensson, N.
    Puglia, C.
    Witkowski, N.
    When the Grafting of Double Decker Phthalocyanines on Si(100)-2 x 1 Partly Affects the Molecular Electronic Structure2016Inngår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 120, nr 26, s. 14270-14276Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A combined X-ray photoelectron spectroscopy (XPS), scanning tunneling microscopy (STM), and density functional theory (DFT) study has been performed to characterize the adsorbate interaction of lutetium biphthalocyanine (LuPc2) molecules on the Si(100)-2 X 1 surface. Large molecule substrate adsorption energies are computed and are found to compete with the molecule molecule interactions of the double decker molecules. A particularly good matching between STM images and computed ones confirms the deformation of the molecule upon the absorption process. The comparison between DFT calculations and XP spectra reveals that the electronic distribution in the two plateaus of the biphthalocyanine are not affected in the same manner upon the adsorption onto the silicon surface. This finding can be of particular importance in the implementation of organic molecules in hybrid devices.

  • 38.
    Bidermane, Ieva
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Materialteori.
    Lüder, Johann
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Materialteori.
    Ahmadi, S.
    Materialfysik, KTH-Electrum.
    Grazioli, C.
    CNR-IOM, Laboratorio TASC.
    Bouvet, M.
    Institut de Chimie Moléculaire de l’Université de Bourgogne.
    Brena, Barbara
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Materialteori.
    Mårtensson, Niklas
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Molekyl- och kondenserade materiens fysik.
    Puglia, Carla
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Molekyl- och kondenserade materiens fysik.
    Witkowski, N.
    Institut des Nanosciences de Paris, UPMC.
    When the Grafting of Double Decker Phthalocyanines on Si(100)-2 × 1 Partly Affects the Molecular Electronic Structure2016Inngår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 120, nr 26, s. 14270-14276Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A combined X-ray photoelectron spectroscopy (XPS), scanning tunneling microscopy (STM), and density functional theory (DFT) study has been performed to characterize the adsorbate interaction of lutetium biphthalocyanine (LuPc2) molecules on the Si(100)-2 × 1 surface. Large molecule–substrate adsorption energies are computed and are found to compete with the molecule–molecule interactions of the double decker molecules. A particularly good matching between STM images and computed ones confirms the deformation of the molecule upon the absorption process. The comparison between DFT calculations and XP spectra reveals that the electronic distribution in the two plateaus of the biphthalocyanine are not affected in the same manner upon the adsorption onto the silicon surface. This finding can be of particular importance in the implementation of organic molecules in hybrid devices.

  • 39. Birke, R. L.
    et al.
    Lombardi, J. R.
    Saidi, W. A.
    Norman, P.
    Surface-Enhanced Raman Scattering Due to Charge-Transfer Resonances: A Time-Dependent Density Functional Theory Study of Ag13-4-Mercaptopyridine2016Inngår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 120, nr 37, s. 20721-20735Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We have used time-dependent density functional theory in conjunction with the CAM-B3LYP functional and MWB28/aug-cc-pVDZ basis set to determine non-, near-, and on-resonance Raman spectra for a complex formed by 4-mercaptopyridine (4-Mpy) binding with a Ag13 cluster via the thiolate Ag-S bond. Geometry optimizations of the Ag13-4-Mpy complex showed an on-top structure directly bound to one Ag atom with the ring of the molecule almost flat with respect to two Ag atoms of the complex. The corresponding B3LYP/MWB28/aug-cc-pVDZ geometry is also an on-top structure directly bound to one Ag atom, but the molecule is directed away from the surface. The near-resonance Raman calculations were carried out in the infinite lifetime approximation, while the on-resonant Raman excitation profiles were calculated with the complex polarization propagator (CPP) approach, introducing a half width at half-maximum spectral broadening of 0.2 eV. Calculation of the UV-vis spectra of the isolated 4-Mpy and of the Ag13-4-Mpy complex showed that binding shifts the spectra from deep in the UV to the visible region. Calculation of the near-resonance Raman spectra of the two structures of the complex at 410 (3.025 eV) and 425 nm (2.918 eV) showed a strong enhancement. A very large variation across vibrational modes by a factor of at least 103 was found for both the static chemical enhancement and charge-transfer (CT) enhancement mechanisms. This large variation in enhancement factor indicates that B-term Herzberg-Teller scattering is occurring because inactive or very low intensity modes in the static spectra of the molecule are much stronger in both the static and near-resonance spectra of the complex. From the excitation profile using the CPP method, an overall surface enhancement on the order 103 or higher was found for individual modes on excitation into a CT excited state. © 2016 American Chemical Society.

  • 40.
    Birke, Ronald L.
    et al.
    CUNY City Coll, NY 10031 USA; CUNY, NY 10016 USA.
    Lombardi, John R.
    CUNY City Coll, NY 10031 USA; CUNY, NY 10016 USA.
    Saidi, Wissam A.
    University of Pittsburgh, PA USA.
    Norman, Patrick
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk kemi. Linköpings universitet, Tekniska fakulteten.
    Surface-Enhanced Raman Scattering Due to Charge-Transfer Resonances: A Time-Dependent Density Functional Theory Study of Ag-13-4-Mercaptopyridine2016Inngår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 120, nr 37, s. 20721-20735Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We have used time-dependent density functional theory in conjunction with the CAM-B3LYP functional and MWB28/aug-cc-pVDZ basis set to determine non-, near-, and on-resonance Raman spectra for a complex formed by 4-mercaptopyridine (4-Mpy) binding with a Ag-13 cluster via the thiolate Ag-S bond. Geometry optimizations of the Ag-13-4-mpy complex showed an on-top structure directly bound to one Ag atom with the ring of the molecule almost flat with respect to two Ag atoms of the complex. The corresponding B3LYP/MWB28/aug-cc-pVDZ geometry is also an on-top structure directly bound to one Ag atom, but the molecule is directed away from the surface,. The near-resonance Raman calculations were carried out in the infinite lifetime approximation, while the on-resonant Raman excitation profiles were calculated with the complex polarization propagator (CPP) approach, introducing a half width at half-maximum spectral broadening of 0.2 eV. Calculation of the UV-vis spectra of the isolated 4-Mpy and of the Ag-13-4-Mpy complex showed that binding shifts the spectra from deep in the UV to the visible region. Calculation of the near-resonance Raman spectra of the two structures of the complex at 410 (3.025 eV) and 425 nm (2.918 eV) showed a strong enhancement. A very large variation across vibrational modes by a factor of at least 10(3) was found for both the static chemical enhancement and charge-transfer (CT) enhancement mechanisms. ThiS large variation in enhancement factor indicates that B-term Herzberg-Teller scattering is occurring because inactive or very low intensity modes in the static spectra of the molecule are much stronger in both the static and near-resonance spectra of the Complex. From the excitation profile using the CPP method, an overall surface enhancement on the order 10(3) or higher was found for individual modes on excitation into a CT excited state.

  • 41.
    Bjorkbacka, Asa
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Tillämpad fysikalisk kemi.
    Johnson, C. Magnus
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Leygraf, Christofer
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Jonsson, Mats
    KTH, Skolan för kemivetenskap (CHE), Kemi, Tillämpad fysikalisk kemi.
    Role of the Oxide Layer in Radiation-Induced Corrosion of Copper in Anoxic Water2016Inngår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 120, nr 21, s. 11450-11455Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The influence of a pregrown copper oxide layer on radiation-induced corrosion of polished copper in pure anoxic water has been explored. The resulting amount of copper oxide formed during corrosion was measured with cathodic reduction, and the concentration of dissolved copper in solution was measured with inductively coupled plasma atomic emission spectroscopy. The identity of corrosion products and their topography was determined with Raman spectroscopy and scanning electron microscopy, respectively. Nonirradiated reference samples were analyzed for comparison. The results show that radiation-induced corrosion of copper in anoxic water is significantly more effective on preoxidized copper compared to polished copper. The total amount of oxidized copper exceeds the amount expected solely from radiation chemistry of water by more than 3 orders of magnitude. To explain this discrepancy a mechanism is suggested where the hydroxyl radical (HO center dot) is the main radiolytic oxidative species driving the corrosion process. If the thermodynamic driving force would be large enough (such as for the hydroxyl radical or its precursor, H2O+), the oxide layer could conduct electrons from the metal to the hydroxyl radicals formed at oxide surfaces. The formation of an oxide layer will then result in an increased reactive surface area partly accounting for the observed discrepancy.

  • 42.
    Björk, Jonas
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk kemi. Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik. Linköpings universitet, Tekniska fakulteten. Linköping University.
    Thermodynamics of an Electrocyclic Ring-Closure Reaction on Au(111)2016Inngår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 120, nr 38, s. 21716-21721Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We have computationally studied the effects of temperature on the reaction pathway of an electrocyclic ring-closure reaction on the Au(111) surface, particularly focusing on thermodynamic aspects of the reaction. The electrocyclic ring closure is accompanied by a series of dehydrogenation steps, and while it is found that temperature, in terms of vibrational entropy and enthalpy, has a reducing effect on most energy barriers, it does not alter the qualitative appreciation of the reaction kinetics. However, it is found that the way the abstracted hydrogen atoms are treated is crucial for the thermodynamics of the reaction. The overall reaction is highly endothermic but becomes thermodynamically favorable due to the entropy gain of the hydrogen byproducts, which desorb associatively from the surface as H2. The study provides new outlooks for the theoretical treatment of reactions related to on-surface synthesis, anticipated to be instructive for future studies.

  • 43.
    Björk, Jonas
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Beräkningsfysik. Linköpings universitet, Tekniska högskolan.
    Zhang, Yi-Qi
    Technische Universität München, Garching, Germany.
    Klappenberger, Florian
    Technische Universität München, Garching, Germany.
    Barth, Johannes V.
    Technische Universität München, Garching, Germany.
    Stafström, Sven
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Beräkningsfysik. Linköpings universitet, Tekniska högskolan.
    Unraveling the Mechanism of the Covalent Coupling Between Terminal Alkynes on a Noble Metal2014Inngår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 118, nr 6, s. 3181-3187Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The mechanism of the newly reported route for surface-assisted covalent coupling of terminal alkynes on Ag(111) is unraveled by density functional theory based transition state calculations. We illustrate that the reaction path is fundamentally different from the classical coupling schemes in wet chemistry. It is initiated by the covalent coupling between two molecules instead of single-molecule dehydrogenation. The silver substrate is found to play an important role stabilizing the intermediate species by chemical bonds, although it is hardly active electronically in the actual coupling step. The dimer intermediate is concluded to undergo two subsequent dehydrogenation processes expected to be rate-limiting according to the comparatively large barriers, which origin is discussed.

  • 44.
    Björneholm, Olle
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Molekyl- och kondenserade materiens fysik.
    Werner, Josephina
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Molekyl- och kondenserade materiens fysik.
    Ottosson, Niklas
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Molekyl- och kondenserade materiens fysik.
    Öhrwall, Gunnar
    Ekholm, Victor
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Molekyl- och kondenserade materiens fysik.
    Winter, Bernd
    Unger, Isaak
    Söderström, Johan
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Molekyl- och kondenserade materiens fysik.
    Deeper Insight into Depth-Profiling of Aqueous Solutions Using Photoelectron Spectroscopy2014Inngår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 118, nr 50, s. 29333-29339Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    X-ray photoelectron spectroscopy (XPS) is widely used to probe properties such as molecular stoichiometry, microscopic distributions relative to the surface by so-called "depth-profiling", and molecular orientation. Such studies usually rely on the core-level photoionization cross sections being independent of molecular composition. The validity of this assumption has recently been questioned, as a number of gas-phase molecules have been shown to exhibit photon-energy-dependent nonstochiometric intensity oscillations arising from EXAFS-like modulations of the photoionization cross section. We have studied this phenomenon in trichloroethanol in both gas phase and dissolved in water. The gas-phase species exhibits pronounced intensity oscillations, similar to the ones observed for other gas-phase molecules. These oscillations are also observed for the dissolved species, implying that the effect has to be taken into account when performing depth-profiling experiments of solutions and other condensed matter systems. The similarity between the intensity oscillations for gas phase and dissolved species allows us to determine the photoelectron kinetic energy of maximum surface sensitivity, ~100 eV, which lies in the range of pronounced intensity oscillations.

  • 45. Blomquist, J.
    et al.
    Walle, L. E.
    Uvdal, P.
    Borg, A.
    Sandell, A.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och materialvetenskap, Yt- och gränsskiktsvetenskap. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Molekyl- och kondenserade materiens fysik.
    Water Dissociation on Single Crystalline Anatase TiO2(001) Studied by Photoelectron Spectroscopy2008Inngår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 112, nr 42, s. 16616-16621Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The adsorption of water on the anatase TiO2(001)-(4 x 1) surface is studied using synchrotron radiation-excited core level photoelectron spectroscopy. The coverage-dependent adsorption of water at low temperature is monitored and compared to the sequence obtained after heating of a water multilayer. Two adsorption phases of submonolayer coverage can be defined: Phase 1 consists only of dissociated water, observed as OH-groups. This phase is found at low coverage at low temperature (190 K) and is the only state of adsorbed water above similar to 230 K. The saturation coverage of phase 1 is consistent with dissociation on the 4-fold-coordinated Ti ridge atoms of the (4 x 1) surface reconstruction. Phase 2 is found at higher coverage, reached at lower temperature. It consists of a mixture of dissociated and molecular water with a ratio of 1:1 at 170 K. The molecular water is found to bond to the hydroxyl groups. The hydroxyl coverage of phase 2 is approximately 2 times that of phase 1. The results suggest that the OH and H2O species of phase 2 are confined to the ridges of the surface.

  • 46.
    Boily, Jean-Francois
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Water Structure and Hydrogen Bonding at Goethite/Water Interfaces: Implications for Proton Affinities2012Inngår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 116, nr 7, s. 4714-4724Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Molecular dynamics simulations of four crystallographic terminations of goethite (alpha-FeOOH) in contact with liquid water (300 K, 1 bar) were performed to resolve interfacial water structures in the vicinity of surface (hydr)oxo groups. Interfacial water molecules adopted highly surface-specific configurations on (010), 100), (110), and (021) planes of goethite. Water molecules generally had weaker hydrogen bond numbers and strengths, as well as smaller self-diffusion coefficients, than their bulk liquid counterparts. Relaxed surface Fe-O and H acceptor distances and populations were used to estimate proton affinity constants of singly-, and triply-coordinated (hydr)oxo groups using the multisite complexation model. These calculations confirmed that singly coordinated groups are mainly responsible for charge uptake under normal environmental conditions. However, revised proton affinity constants showed that protonation of doubly-coordinated hydroxo groups and one type of triply-coordinated oxo group may be favored in the presence of strongly binding negatively charged ligands. These calculations should facilitate elucidation of surface complexation mechanisms on this environmentally important material.

  • 47.
    Boily, Jean-Francois
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Lins, Roberto D
    Pacific Northwest National Laboratory, Richland Washington, USA .
    Electrostatic cooperativity of hydroxyl groups at metal oxide surfaces2009Inngår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 113, nr 38, s. 16568-16570Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The O−H bond distribution of hydroxyl groups at the {110} goethite (α-FeOOH) surface was investigated by molecular dynamics. This distribution was strongly affected by electrostatic interactions with neighboring oxo and hydroxo groups. The effects of proton surface loading, simulated by emplacing two protons at different distances of separation, were diverse and generated several sets of O−H bond distributions. DFT calculations of a representative molecular cluster were also carried out to demonstrate the impact of these effects on the orientation of oxygen lone pairs in neighboring oxo groups. These effects should have strong repercussions on O−H stretching vibrations of metal oxide surfaces.

  • 48.
    Boily, Jean-Francois
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Shchukarev, Andrey
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    X-ray photoelectron spectroscopy of fast-frozen hematite colloids in aqueous solutions. 2. tracing the relationship between surface charge and electrolyte adsorption2010Inngår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 114, nr 6, s. 2613-2616Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Colloidal-sized hematite spheroids exposed to aqueous NaCl solutions were investigated by X-ray photoelectron spectroscopy using the fast-frozen technique. The O 1s region provided evidence for (de)protonation reactions of surface (hydr)oxo groups of OH-enriched/O-depleted hematite Surfaces. These results were also correlated to changes in sodium (Na 1s) and chloride (Cl 2p) contents with pH. Electrolyte ion surface loadings were successfully predicted using a classic thermodynamic adsorption model normalized for surface site density. These efforts pointed to ion-specific inner-Helmholtz plane capacitances.

  • 49.
    Borges, J.
    et al.
    Univ Minho, Ctr Fis, Campus Gualtar, P-4710057 Braga, Portugal.;Czech Tech Univ, Fac Elect Engn, Dept Control Engn, Tech 2, Prague 6, Czech Republic.;Inst Pedro Nunes, Lab Ensaios Desgaste & Mat, Rua Pedro Nunes, P-3030199 Coimbra, Portugal.;Univ Coimbra, SEG CEMUC, Mech Engn Dept, P-3030788 Coimbra, Portugal..
    Pereira, R. M. S.
    Univ Minho, Ctr Fis, Campus Gualtar, P-4710057 Braga, Portugal.;Univ Minho, Ctr Matemat, Campus Gualtar, P-4710057 Braga, Portugal.;Univ Minho, Dept Matemat & Aplicacoes, Campus Gualtar, P-4710057 Braga, Portugal..
    Rodrigues, M. S.
    Univ Minho, Ctr Fis, Campus Gualtar, P-4710057 Braga, Portugal.;Inst Pedro Nunes, Lab Ensaios Desgaste & Mat, Rua Pedro Nunes, P-3030199 Coimbra, Portugal..
    Kubart, Tomas
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets elektronik.
    Kumar, Saroj
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets elektronik.
    Leifer, Klaus
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets elektronik.
    Cavaleiro, A.
    Univ Coimbra, SEG CEMUC, Mech Engn Dept, P-3030788 Coimbra, Portugal..
    Polcar, T.
    Czech Tech Univ, Fac Elect Engn, Dept Control Engn, Tech 2, Prague 6, Czech Republic.;Univ Southampton, Natl Ctr Adv Tribol Southampton nCATS, Southampton SO17 1BJ, Hants, England..
    Vasilevskiy, M. I.
    Univ Minho, Ctr Fis, Campus Gualtar, P-4710057 Braga, Portugal.;City Univ Hong Kong, Dept Phys & Mat Sci, Hong Kong, Hong Kong, Peoples R China.;City Univ Hong Kong, CFP, Hong Kong, Hong Kong, Peoples R China..
    Vaz, F.
    Univ Minho, Ctr Fis, Campus Gualtar, P-4710057 Braga, Portugal..
    Broadband Optical Absorption Caused by the Plasmonic Response of Coalesced Au Nanoparticles Embedded in a TiO2 Matrix2016Inngår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 120, nr 30, s. 16931-16945Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The effect of Au nanopattides' (NPs) concentration, site, and spatial distribution within a TiO2 dielectric matrix on the localized surface plasmon resonance (LSPR) band characteristics was experimentally and theoretically studied. The results of the analysis of the Au NPs' size distributions allowed us to conclude that isolated NPs grow only up to 5 to 6 nm in site, even for the highest annealing temperature used. However, for higher volume fractions of Au, the coalescence of closely located NPs yields elongated clusters that are much larger in size and cause a considerable broadening of the LSPR band. This effect was confirmed by Monte Carlo modeling results. Coupled dipole equations were solved to find the electromagnetic modes of a supercell, where isolated and coalesced NPs were distributed, from which an effective dielectric function of the nanocomposite material was calculated and used to evaluate the optical transmittance and reflectance spectra. The modeling results suggested that the observed LSPR band broadening is due to a wider spectral distribution of plasmonic modes, caused by the presence of coalesced NPs (in addition to the usual damping effect). This is particularly important for detection applications via surface-enhanced Raman spectroscopy (SERS), where it is desirable to have a spectrally broad LSPR band in order:to favor the fulfillment of the conditions of resonance matching, to electronic transitions in detected species.

  • 50.
    Bounechada, Djamela
    et al.
    Chalmers, Dept Chem & Biol Engn, SE-41296 Gothenburg, Sweden Chalmers, Competence Ctr Catalysis, SE-41296 Gothenburg, Sweden .
    Darmastuti, Zhafira
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tillämpad sensorvetenskap. Linköpings universitet, Tekniska högskolan.
    Andersson, Mike
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tillämpad sensorvetenskap. Linköpings universitet, Tekniska högskolan.
    Ojamäe, Lars
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Kemi. Linköpings universitet, Tekniska högskolan.
    Lloyd Spetz, Anita
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tillämpad sensorvetenskap. Linköpings universitet, Tekniska högskolan.
    Skoglundh, Magnus
    Chalmers, Dept Chem & Biol Engn, SE-41296 Gothenburg, Sweden Chalmers, Competence Ctr Catalysis, SE-41296 Gothenburg, Sweden.
    Carlsson, Per-Anders
    Chalmers, Dept Chem & Biol Engn, SE-41296 Gothenburg, Sweden Chalmers, Competence Ctr Catalysis, SE-41296 Gothenburg, Sweden.
    Vibrational Study of SOx Adsorption on Pt/SiO22014Inngår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 118, nr 51, s. 29713-29723Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The formation of ad-SOx species on Pt/SiO2 upon exposure to SO2 in concentrations ranging from 10 to 50 ppm at between 200 and 400 degrees C has been studied by in situ diffuse reflectance infrared Fourier transformed spectroscopy. In parallel, first-principles calculations have been carried out to consolidate the experimental interpretations. It was found that sulfate species form on the silica surface with a concomitant removal/rearrangement of silanol groups. Formation of ad-SOx species occurs only after SO2 oxidation to SO3 on the platinum surface. Thus, SO2 oxidation to SO3 is the first step in the SOx adsorption process, followed by spillover of SO3 to the oxide, and finally, the formation of sulfate species on the hydroxyl positions on the oxide. The sulfate formation is influenced by both temperature and SO2 concentration. Furthermore, exposure to hydrogen is shown to be sufficiently efficient as to remove ad-SOx species from the silica surface.

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