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  • 201.
    Coupette, Fabian
    et al.
    Univ Freiburg, Inst Phys, Hermann Herder Str 3, D-79104 Freiburg, Germany..
    Zhang, Long
    INM Leibniz Inst New Mat, Campus D2 2, D-66123 Saarbrucken, Germany..
    Kuttich, Bjoern
    INM Leibniz Inst New Mat, Campus D2 2, D-66123 Saarbrucken, Germany..
    Chumakov, Andrei
    Deutsch Elektronen Synchrotron DESY, Notkestr 85, D-22607 Hamburg, Germany..
    Roth, Stephan V.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology. Deutsch Elektronen Synchrotron DESY, Notkestr 85, D-22607 Hamburg, Germany.;.
    Gonzalez-Garcia, Lola
    INM Leibniz Inst New Mat, Campus D2 2, D-66123 Saarbrucken, Germany..
    Kraus, Tobias
    INM Leibniz Inst New Mat, Campus D2 2, D-66123 Saarbrucken, Germany.;Saarland Univ, Colloid & Interface Chem, Campus D2 2, D-66123 Saarbrucken, Germany..
    Schilling, Tanja
    Univ Freiburg, Inst Phys, Hermann Herder Str 3, D-79104 Freiburg, Germany..
    Percolation of rigid fractal carbon black aggregates2021In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 155, no 12, article id 124902Article in journal (Refereed)
    Abstract [en]

    We examine network formation and percolation of carbon black by means of Monte Carlo simulations and experiments. In the simulation, we model carbon black by rigid aggregates of impenetrable spheres, which we obtain by diffusion-limited aggregation. To determine the input parameters for the simulation, we experimentally characterize the micro-structure and size distribution of carbon black aggregates. We then simulate suspensions of aggregates and determine the percolation threshold as a function of the aggregate size distribution. We observe a quasi-universal relation between the percolation threshold and a weighted average radius of gyration of the aggregate ensemble. Higher order moments of the size distribution do not have an effect on the percolation threshold. We conclude further that the concentration of large carbon black aggregates has a stronger influence on the percolation threshold than the concentration of small aggregates. In the experiment, we disperse the carbon black in a polymer matrix and measure the conductivity of the composite. We successfully test the hypotheses drawn from simulation by comparing composites prepared with the same type of carbon black before and after ball milling, i.e., on changing only the distribution of aggregate sizes in the composites.& nbsp;

  • 202.
    Couto, Rafael Carvalho
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Theoretical Chemistry and Biology.
    Hua, W.
    Lindblad, R.
    Kjellsson, L.
    Sorensen, S. L.
    Kubin, M.
    Bülow, C.
    Timm, M.
    Zamudio-Bayer, V.
    Von Issendorff, B.
    Söderström, J.
    Lau, J. T.
    Rubensson, J. -E
    Ågren, H.
    Carravetta, V.
    Breaking inversion symmetry by protonation: Experimental and theoretical NEXAFS study of the diazynium ion, N2H+2021In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 23, no 32, p. 17166-17176Article in journal (Refereed)
    Abstract [en]

    As an example of symmetry breaking in NEXAFS spectra of protonated species we present a high resolution NEXAFS spectrum of protonated dinitrogen, the diazynium ion N2H+. By ab initio calculations we show that the spectrum consists of a superposition of two nitrogen 1s absorption spectra, each including a π∗ band, and a nitrogen 1s to H+ charge transfer band followed by a weak irregular progression of high energy excitations. Calculations also show that, as an effect of symmetry breaking by protonation, the π∗ transitions are separated by 0.23 eV, only slightly exceeding the difference in the corresponding dark (symmetry forbidden) and bright (symmetry allowed) core excitations of neutral N2. By DFT and calculations and vibrational analysis, the complex π∗ excitation band of N2H+ is understood as due to the superposition of the significantly different vibrational progressions of excitations from terminal and central nitrogen atoms, both leading to bent final state geometries. We also show computationally that the electronic structure of the charge transfer excitation smoothly depends on the nitrogen-proton distance and that there is a clear extension of the spectra going from infinity to close nitrogen-proton distance where fine structures show some, although not fully detailed, similarities. An interesting feature of partial localization of the nitrogen core orbitals, with a strong, non-monotonous, variation with nitrogen-proton distance could be highlighted. Specific effects could be unraveled when comparing molecular cation NEXAFS spectra, as represented by recently recorded spectra of N2+ and CO+, and spectra of protonated molecules as represented here by the N2H+ ion. Both types containing rich physical effects not represented in NEXAFS of neutral molecules because of the positive charge, whereas protonation also breaks the symmetry. The effect of the protonation on dinitrogen can be separated in charge, which extends the high-energy part of the spectrum, and symmetry-breaking, which is most clearly seen in the low-energy π∗ transition.

  • 203.
    Couto, Rafael Carvalho
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Theoretical Chemistry and Biology.
    Kjellsson, Ludvig
    Uppsala Univ, Dept Phys & Astron, Box 516, SE-75120 Uppsala, Sweden.;European XFEL GmbH, Holzkoppel 4, D-22869 Schenefeld, Germany..
    Ågren, Hans
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Theoretical Chemistry and Biology. Uppsala Univ, Dept Phys & Astron, Box 516, SE-75120 Uppsala, Sweden.;Tomsk State Univ, 36 Lenin Ave, Tomsk, Russia..
    Carravetta, Vincenzo
    IPCF CNR, Via Moruzzi 1, I-56124 Pisa, Italy..
    Sorensen, Stacey L.
    Lund Univ, Dept Phys, Box 118, S-22100 Lund, Sweden..
    Kubin, Markus
    Helmholtz Zentrum Berlin Mat & Energie, Abt Hochempfindl Rontgenspektroskopie, Albert Einstein Str 15, D-12489 Berlin, Germany..
    Buelow, Christine
    Helmholtz Zentrum Berlin Mat & Energie, Abt Hochempfindl Rontgenspektroskopie, Albert Einstein Str 15, D-12489 Berlin, Germany..
    Timm, Martin
    Helmholtz Zentrum Berlin Mat & Energie, Abt Hochempfindl Rontgenspektroskopie, Albert Einstein Str 15, D-12489 Berlin, Germany..
    Zamudio-Bayer, Vicente
    Helmholtz Zentrum Berlin Mat & Energie, Abt Hochempfindl Rontgenspektroskopie, Albert Einstein Str 15, D-12489 Berlin, Germany..
    von Issendorff, Bernd
    Albert Ludwigs Univ Freiburg, Phys Inst, Hermann Herder Str 3, D-79104 Freiburg, Germany..
    Lau, J. Tobias
    Helmholtz Zentrum Berlin Mat & Energie, Abt Hochempfindl Rontgenspektroskopie, Albert Einstein Str 15, D-12489 Berlin, Germany.;Albert Ludwigs Univ Freiburg, Phys Inst, Hermann Herder Str 3, D-79104 Freiburg, Germany..
    Söderström, Johan
    Uppsala Univ, Dept Phys & Astron, Box 516, SE-75120 Uppsala, Sweden..
    Rubensson, Jan-Erik
    Uppsala Univ, Dept Phys & Astron, Box 516, SE-75120 Uppsala, Sweden..
    Lindblad, Rebecka
    Lund Univ, Dept Phys, Box 118, S-22100 Lund, Sweden.;Helmholtz Zentrum Berlin Mat & Energie, Abt Hochempfindl Rontgenspektroskopie, Albert Einstein Str 15, D-12489 Berlin, Germany.;Uppsala Univ, Inorgan Chem, Dept Chem, Angstrom Lab, SE-75121 Uppsala, Sweden..
    The carbon and oxygen K-edge NEXAFS spectra of CO+2020In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 22, no 28, p. 16215-16223Article in journal (Refereed)
    Abstract [en]

    We present and analyze high resolution near edge X-ray absorption fine structure (NEXAFS) spectra of CO(+)at the carbon and oxygen K-edges. The spectra show a wealth of features that appear very differently at the two K-edges. The analysis of these features can be divided into three parts; (i) repopulation transition to the open shell orbital - here the C(1s) or O(1s) to 5 sigma transition, where the normal core hole state is reached from a different initial state and different interaction than in X-ray photoelectron spectroscopy; (ii) spin coupled split valence bands corresponding to C(1s) or O(1s) to pi* transitions; (iii) remainder weak and long progressions towards the double ionization potentials containing a manifold of peaks. These parts, none of which has correspondence in NEXAFS spectra of neutral molecules, are dictated by the localization of the singly occupied 5 sigma orbital, adding a dimension of chemistry to the ionic NEXAFS technique.

  • 204.
    Cuartero, Maria
    et al.
    Univ Geneva, Dept Inorgan & Analyt Chem, Quai Ernest Ansermet 30, CH-1211 Geneva, Switzerland..
    Acres, Robert G.
    ANSTO, Australian Synchrotron, 800 Blackburn Rd, Clayton, Vic 3168, Australia..
    Jarolimova, Zdenka
    Univ Geneva, Dept Inorgan & Analyt Chem, Quai Ernest Ansermet 30, CH-1211 Geneva, Switzerland..
    Bakker, Eric
    Univ Geneva, Dept Inorgan & Analyt Chem, Quai Ernest Ansermet 30, CH-1211 Geneva, Switzerland..
    Crespo, Gaston A.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry. Univ Geneva, Dept Inorgan & Analyt Chem, Quai Ernest Ansermet 30, CH-1211 Geneva, Switzerland.
    De Marco, Roland
    Univ Sunshine Coast, Fac Sci Hlth Educ & Engn, 90 Sippy Downs Dr, Sippy Downs, Qld 4556, Australia.;Univ Queensland, Sch Chem & Mol Biosci, Brisbane, Qld 4072, Australia.;Curtin Univ, Dept Chem, GPO Box U1987, Perth, WA 6109, Australia..
    Electron Hopping between Fe 3d States in Ethynylferrocene-doped Poly(Methyl Methacrylate)-poly(Decyl Methacrylate) Copolymer Membranes2018In: Electroanalysis, ISSN 1040-0397, E-ISSN 1521-4109, Vol. 30, no 4, p. 596-601Article in journal (Refereed)
    Abstract [en]

    Synchrotron radiation-valence band spectroscopy (SR-VBS) has been utilized in a study of redox molecule valence states implicated in the electron hopping mechanism of ethynylferrocene in unplasticized poly(methyl methacrylate)-poly(decyl methacrylate) [PMMA-PDMA] membranes. In this communication, it is revealed that, at high concentrations of ethynylferrocene, there are observable Fe 3d valence states that are likely linked to electron hopping between ferrocene moieties of neighbouring redox molecules. Furthermore, electrochemically induced stratification of ethynylferrocene in an oxidized PMMA-PDMA membrane produces a gradient of Fe 3d states toward the buried interface at the glassy carbon/PMMA-PDMA membrane enabling electron hopping and electrochemical reactivity of dissolved ethynylferrocene across this buried film.

  • 205.
    Cuartero, Maria
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Crespo, Gaston A.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    All-solid-state potentiometric sensors: A new wave for in situ aquatic research2018In: Current Opinion in Electrochemistry, E-ISSN 2451-9103, Vol. 10, p. 98-106Article in journal (Refereed)
    Abstract [en]

    Over the last few years, all-solid-state potentiometric ion-selective sensors have demonstrated a huge potential for environmental water analysis. Beyond the excellent analytical performances exhibited in benchtop conditions for the detection of important targets (e.g. pH, species relevant to the carbon and nitrogen cycles, trace metals), the challenge now lies in bringing those sensors to in situ format and obtaining valuable chemical information directly in the field while minimizing or avoiding the need for sampling. Technically speaking, the instrumentation for potentiometric assessment is extremely simple, low cost and requires minimal space. In addition, the all-solid-state configuration seems ideal to fabricate miniaturized sensors with sufficient analytical performance to detect certain ions in water resources. Herein, we highlight the power of all-solid-state potentiometric sensors applied to environmental water analysis providing a threefold overview: (i) the recent materials used in the fabrication of all-solid-state polymeric membrane electrodes, both the solid contact and ion-selective membrane; (ii) a collection of the main targets explored during the last 5 years; and (iii) examples of the most recent and relevant in situ applications employing submersible equipment. Throughout the review, issues such as ‘What are the real implications of all-solid-state membrane electrodes in the environmental field?’ and ‘To what extent has the effort in developing new sensors over time been well-exploited?’ are addressed. Convincingly, all-solid-state potentiometric sensors are positioning as a unique in situ interface providing real-time data that allow for an understanding of ongoing biogeochemical processes and possible anthropogenic activities implications.

  • 206.
    Cuartero, Maria
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Crespo, Gaston A.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Using Potentiometric Electrodes Based on Nonselective Polymeric Membranes as Potential Universal Detectors for Ion Chromatography: Investigating an Original Research Problem from an Inquiry-Based-Learning Perspective2018In: Journal of Chemical Education, ISSN 0021-9584, E-ISSN 1938-1328, Vol. 95, no 12, p. 2172-2181Article in journal (Refereed)
    Abstract [en]

    Because traditional laboratory practices in advanced chemistry education are being replaced by inquiry based approaches, we present herein a new laboratory activity based on a small research project that was designed and executed by students. The laboratory project aims at answering a well-defined research question: how far can potentiometric electrodes based on nonselective polymeric membranes be used as universal detectors in ion chromatography (IC)? Hence, the experiments were designed and conducted to explore the analytical performances of potentiometric electrodes based on different commercial membranes that are typically used in electrodialysis. The nonselective behavior shown by the electrodes permits a critical evaluation of their further implementation as a universal detector of anions in regular IC. Thus, the students were able to integrate a nonselective potentiometric sensor to analyze several anions in flow mode, mimicking the signal that is to be obtained using such electrodes as an IC detector. The proposed practice covers different pedagogical purposes: (i) to develop competence toward "thinking like a scientist" through reflective teaching; (ii) to promote argumentation skills and critical decision making; (iii) to improve students' research-planning and experimental-design skills; (iv) to refresh conceptual knowledge about analytical detectors, which typically goes unnoticed in laboratory practices; and (v) to reinforce students' knowledge about the basis of potentiometry. Furthermore, the present document may serve as an easy guide to develop other laboratory practices based on potentiometric sensors.

  • 207.
    Cui, Yuxiao
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Polymeric Materials.
    Sheng, Xia
    Henan Agricultural University, Coll Sci, Zhengzhou, 450000, China.
    Anusuyadevi, Prasaanth Ravi
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Lawoko, Martin
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Svagan, Anna Justina
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Self-assembled carbon spheres prepared from abundant lignin and urea for photocatalytic and self-propelling applications2021In: Carbon Trends, ISSN 2667-0569, Vol. 3, p. 100040-, article id 100040Article in journal (Refereed)
    Abstract [en]

    Lignin is a valuable bio-resource in the manufacturing of carbon-based functional materials, because of its large carbon content (~60%), various phenolic structural units, abundancy and sustainability. Here, we explored its use in photocatalytic and self-propelling applications. First, hydroxyl-abundant lignin-based carbon precursor particles, HCLSs, were produced by hydrothermal carbonization of lignin-based microcapsules (LCs). Then, by heating urea coated HCLSs, carbon spheres with a layer of graphitic carbon nitride (g-C3N4) were produced. The presence of surface available -OH groups on the HCLSs, were critical in the formation mechanism. Under visible-light irradiation, the photocatalytic spheres exhibited enhanced activity (49% of the model pollutant remained after 60 min, at 100 mW cm−2) and possessed a three times higher average removal rate constant compared to that of g-C3N4 powder. The g-C3N4 powder was obtained when heating urea only. Additionally, by introducing a Pt/Pd coating on only one side of the composite spheres, the spheres were made self-propelling in the presence of a fuel (H2O2). This work provides new insights into the preparation principles of lignin-based photocatalytic spheres for effective solar photocatalysis applications.

  • 208.
    Cullari, Lucas Luciano
    et al.
    Ben Gurion Univ Negev, Dept Chem Engn, IL-8410501 Beer Sheva, Israel..
    Masiach, Tom
    Ben Gurion Univ Negev, Dept Chem Engn, IL-8410501 Beer Sheva, Israel..
    Damari, Sivan Peretz
    Ben Gurion Univ Negev, Dept Chem Engn, IL-8410501 Beer Sheva, Israel..
    Ligati, Shani
    Ben Gurion Univ Negev, Dept Chem Engn, IL-8410501 Beer Sheva, Israel..
    Furo, Istvan
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Regev, Oren
    Ben Gurion Univ Negev, Dept Chem Engn, IL-8410501 Beer Sheva, Israel.;Ben Gurion Univ Negev, Ilse Katz Inst Nanoscale Sci & Technol, IL-8410501 Beer Sheva, Israel..
    Trapped and Alone: Clay-Assisted Aqueous Graphene Dispersions2021In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 13, no 5, p. 6879-6888Article in journal (Refereed)
    Abstract [en]

    Dispersing graphene sheets in liquids, in particular water, could enhance the transport properties (like thermal conductivity) of the dispersion. Yet, such dispersions are difficult to achieve since graphene sheets are prone to aggregate and subsequently precipitate due to their strong van der Waals interactions. Conventional dispersion approaches, such as surface treatment of the sheets either by surfactant adsorption or by chemical modification, may prevent aggregation. Unfortunately, surfactant-assisted graphene dispersions are typically of low concentration (<0.2 wt %) with relatively small sheets (<1 mu m lateral size) while chemical modification is punished by increased defect density within the sheets. We investigate here a new approach in which the concentration of dispersed graphene in water is enhanced by the addition of a fibrous clay mineral, sepiolite. As we demonstrate, the clay particles in water form a kinetically arrested particle network within which the graphene sheets are effectively trapped. This mechanism keeps graphene sheets of high lateral size similar to 4 mu m) dispersed at high concentrations (similar to 1 wt %). We demonstrate the application of such dispersions as cooling liquids for thermal management solutions, where a 26% enhancement in the thermal conductivity is achieved as compared to that in a filler-free fluid.

  • 209.
    Cullari, Lucas Luciano
    et al.
    Department of Chemical Engineering, Ben-Gurion University of the Negev, Beer-Sheva 8410501, Israel.
    Yosefi, Gal
    Department of Chemical Engineering, Ben-Gurion University of the Negev, Beer-Sheva 8410501, Israel.
    Nativ-Roth, Einat
    The Ilse Katz Institute for Nanoscale Science and Technology, Ben-Gurion University of the Negev, Beer-Sheva 8410501, Israel.
    Furo, Istvan
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Regev, Oren
    Department of Chemical Engineering, Ben-Gurion University of the Negev, Beer-Sheva 8410501, Israel; The Ilse Katz Institute for Nanoscale Science and Technology, Ben-Gurion University of the Negev, Beer-Sheva 8410501, Israel.
    Decoupling rheology from particle concentration by charge modulation: Aqueous graphene-clay dispersions2024In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 655, p. 863-875Article in journal (Refereed)
    Abstract [en]

    Hypothesis: Aqueous graphene dispersions are usually obtainable by treating the surface of graphene chemically or physically. In these dispersions, the rheological properties (e.g., viscosity) are governed by a direct coupling to the graphene concentration, which limits their applicability. An alternative approach for dispersing graphene is trapping them in a viscoelastic-network formed by a co-dispersed charged fibrous-clay, Sepiolite. Contrary to surface treatment, the rheological properties of these dispersions are set by the clay particles. The rheology of charged-colloidal dispersions is governed by various parameters, including interparticle interactions. Hence, the rheology of the dispersion could be modulated by changing the clay surface charge without compromising the dispersed graphene concentration. Experimental: The surface charge of Sepiolite was modulated either by charge-screening (by NaCl added to the solution) or by surface-charging (by attachment of highly charged ions, e.g., HexaMetaPhosphate, HMP−) and the effect on rheology and graphene concentration was assessed. In particular, loading the dispersion with HMP− yielded low viscosity, storage, and loss moduli (two orders of magnitude lower than the corresponding HMP−-free dispersion) while the graphene concentration was maintained. We demonstrate that by this charge-modulation approach, reaching the rheological requirements of different applications without compromising on graphene concentration is plausible.

  • 210.
    da Cruz, Vinicius Vaz
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Theoretical Chemistry and Biology. Univ Potsdam, Inst Phys & Astron, Karl Liebknecht Str 24-25, D-14476 Potsdam, Germany..
    Ignatova, Nina
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Theoretical Chemistry and Biology. Siberian Fed Univ, Krasnoyarsk 660041, Russia.;Fed Res Ctr KSC SB RAS, Kirensky Inst Phys, Krasnoyarsk 660036, Russia..
    Couto, Rafael C.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Theoretical Chemistry and Biology.
    Fedotov, Daniil A.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Theoretical Chemistry and Biology. Siberian Fed Univ, Krasnoyarsk 660041, Russia..
    Rehn, Dirk R.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Theoretical Chemistry and Biology.
    Savchenko, Viktoriia
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Theoretical Chemistry and Biology. Siberian Fed Univ, Krasnoyarsk 660041, Russia.;Fed Res Ctr KSC SB RAS, Kirensky Inst Phys, Krasnoyarsk 660036, Russia..
    Norman, Patrick
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Theoretical Chemistry and Biology.
    Ågren, Hans
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Theoretical Chemistry and Biology. Uppsala Univ, Dept Phys & Astron, Box 516, SE-75120 Uppsala, Sweden..
    Polyutov, Sergey
    Siberian Fed Univ, Krasnoyarsk 660041, Russia.;Fed Res Ctr KSC SB RAS, Kirensky Inst Phys, Krasnoyarsk 660036, Russia..
    Niskanen, Johannes
    Univ Turku, Dept Phys & Astron, FI-20014 Turun, Finland.;Helmholtz Zentrum Berlin Mat & Energie, Inst Methods & Instrumentat Synchrotron Radiat Re, Albert Einstein Str 15, D-12489 Berlin, Germany..
    Eckert, Sebastian
    Univ Potsdam, Inst Phys & Astron, Karl Liebknecht Str 24-25, D-14476 Potsdam, Germany..
    Jay, Raphael M.
    Univ Potsdam, Inst Phys & Astron, Karl Liebknecht Str 24-25, D-14476 Potsdam, Germany..
    Fondell, Mattis
    Helmholtz Zentrum Berlin Mat & Energie, Inst Methods & Instrumentat Synchrotron Radiat Re, Albert Einstein Str 15, D-12489 Berlin, Germany..
    Schmitt, Thorsten
    Paul Scherrer Inst, Photon Sci Div, CH-5232 Villigen, Switzerland..
    Pietzsch, Annette
    Helmholtz Zentrum Berlin Mat & Energie, Inst Methods & Instrumentat Synchrotron Radiat Re, Albert Einstein Str 15, D-12489 Berlin, Germany..
    Foehlisch, Alexander
    Univ Potsdam, Inst Phys & Astron, Karl Liebknecht Str 24-25, D-14476 Potsdam, Germany.;Helmholtz Zentrum Berlin Mat & Energie, Inst Methods & Instrumentat Synchrotron Radiat Re, Albert Einstein Str 15, D-12489 Berlin, Germany..
    Gel'mukhanov, Faris
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Theoretical Chemistry and Biology. Siberian Fed Univ, Krasnoyarsk 660041, Russia.;Fed Res Ctr KSC SB RAS, Kirensky Inst Phys, Krasnoyarsk 660036, Russia..
    Odelius, Michael
    Stockholm Univ, AlbaNova Univ Ctr, Dept Phys, S-10691 Stockholm, Sweden..
    Kimberg, Victor
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Theoretical Chemistry and Biology. Siberian Fed Univ, Krasnoyarsk 660041, Russia.;Fed Res Ctr KSC SB RAS, Kirensky Inst Phys, Krasnoyarsk 660036, Russia..
    Nuclear dynamics in resonant inelastic X-ray scattering and X-ray absorption of methanol2019In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 150, no 23, article id 234301Article in journal (Refereed)
    Abstract [en]

    We report on a combined theoretical and experimental study of core-excitation spectra of gas and liquid phase methanol as obtained with the use of X-ray absorption spectroscopy (XAS) and resonant inelastic X-ray scattering (RIXS). The electronic transitions are studied with computational methods that include strict and extended second-order algebraic diagrammatic construction [ADC(2) and ADC(2)-x], restricted active space second-order perturbation theory, and time-dependent density functional theory-providing a complete assignment of the near oxygen K-edge XAS. We show that multimode nuclear dynamics is of crucial importance for explaining the available experimental XAS and RIXS spectra. The multimode nuclear motion was considered in a recently developed "mixed representation" where dissociative states and highly excited vibrational modes are accurately treated with a time-dependent wave packet technique, while the remaining active vibrational modes are described using Franck-Condon amplitudes. Particular attention is paid to the polarization dependence of RIXS and the effects of the isotopic substitution on the RIXS profile in the case of dissociative core-excited states. Our approach predicts the splitting of the 2a RIXS peak to be due to an interplay between molecular and pseudo-atomic features arising in the course of transitions between dissociative core- and valence-excited states. The dynamical nature of the splitting of the 2a peak in RIXS of liquid methanol near pre-edge core excitation is shown. The theoretical results are in good agreement with our liquid phase measurements and gas phase experimental data available from the literature.

  • 211.
    Dahlberg, Carina
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry.
    Drugs and polymers in dissolving solid dispersions: NMR imaging and spectroscopy2010Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The number of poorly water-soluble drug substances in the pharmaceutical pipeline is increasing, and thereby also the need to design effective drug delivery systems providing high bioavailability. One favourable formulation approach is preparation of solid dispersions, where dispersing a poorly water-soluble drug in a water-soluble polymer matrix improves the dissolution behaviour and the bioavailability of the drug. However, in order to take full advantage of such formulations the impact of material properties on their performance needs to be investigated.

     

    An experimental toolbox has been designed, and applied, for analysing the processes which govern the behaviour of solid pharmaceutical formulations in general, and that of solid dispersions in particular. For the purpose of monitoring multifaceted phenomena in situ during tablet dissolution, nuclear magnetic resonance (NMR) spectroscopy and NMR imaging are superior to many other techniques, both on macroscopic and molecular levels. The versatility of NMR with its isotope and chemical selectivity allows one to follow the influence of the original tablet properties on polymer mobilisation, drug migration and water penetration selectively. Mapping these processes on relevant time scales in dissolving tablets highlighted the gel layer inhomogeneity below the originally dry tablet surface as a key factor for drug release kinetics.

     

    Furthermore, NMR relaxometry has been shown to provide novel information about the particle size of the drug and its recrystallisation behaviour within swelling solid dispersions. The NMR experiments have been complemented and supported by investigation of the crystalline state, the powder morphology and the surface composition of the dry solid dispersions. These experiments have been performed by X-ray photoelectron spectroscopy (XPS),  scanning electron microscopy (SEM), powder X-ray diffraction (pXRD), differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR) and dynamic contact angle (DAT) measurements.

     

    The methods presented in this thesis provide a new avenue towards better understanding of the behaviour of solid dispersions, which in turn may result in more effective distribution of promising drug candidates despite their low water-solubility.

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  • 212.
    Dahlberg, Carina
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry.
    Dvinskikh, Sergey V.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry.
    Schuleit, Michael
    Furo, Istvan
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry.
    Polymer Swelling, Drug Mobilization and Drug Recrystallization in Hydrating Solid Dispersion Tablets Studied by Multinuclear NMR Microimaging and Spectroscopy2011In: Molecular Pharmaceutics, ISSN 1543-8384, E-ISSN 1543-8392, Vol. 8, no 4, p. 1247-1256Article in journal (Refereed)
    Abstract [en]

    Despite the advantages offered by solid dispersions, the marketed products based on this technology are few. The most frequent concern is the stability of the amorphous drug. The state of the drug in solid dispersions is, in general, poorly characterized as the number of characterization techniques available to monitor nanometer-sized drug particles embedded in a matrix are limited. Here we present a combination of localized NMR spectroscopic and NMR imaging techniques which allow in situ monitoring of the state of the drug during tablet disintegration and dissolution. (19)F NMR relaxation is shown to be sensitive to both the crystalline/amorphous state and the size of the model nanoparticles made of the drug substance flutamide. The time course of drug mobilization and recrystallization is detected with spatial resolution within swelling solid dispersion tablets. Comparing results from spatially resolved (19)F, (2)H and (1)H NMR experiments, recrystallization is related to its enabling factors such as local hydration level and local mobility of the polymer matrix. The initially amorphous drug may recrystallize either by nanoparticle coalescence or by ripening of crystalline grains.

  • 213.
    Dahlberg, Carina
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Industrial NMR Centre.
    Schuleit, Michael
    Furó, István
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Industrial NMR Centre.
    Estimating the size range of drug nanoparticles in solid dispersions by NMR spectroscopyManuscript (preprint) (Other academic)
  • 214.
    Dahlgren, Björn
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Sabatino, Maria Antonietta
    Univ Palermo, Dipartimento Ingn, Viale Sci 6, I-90128 Palermo, Italy..
    Dispenza, Clelia
    Univ Palermo, Dipartimento Ingn, Viale Sci 6, I-90128 Palermo, Italy.;CNR, Ist Biofis IBF, Via U La Malfa 153, I-90146 Palermo, Italy..
    Jonsson, Mats
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Numerical Simulations of Nanogel Synthesis Using Pulsed Electron Beam2020In: Macromolecular Theory and Simulations, ISSN 1022-1344, E-ISSN 1521-3919, Vol. 29, no 1, p. 1900046-, article id 1900046Article in journal (Refereed)
    Abstract [en]

    In this work, a new method for numerical simulation of the radiation chemistry of aqueous polymer solutions exposed to a sequence of electron pulses is presented. The numerical simulations are based on a deterministic approach encompassing the conventional homogeneous radiation chemistry of water as well as the chemistry of polymer radicals. The multitude of possible reactions in the macromolecular system is handled by allowing for a large number of macromolecular species. The speciation of macromolecular species is done to account for variations in molecular weight, number of alkyl radicals per chain, number of peroxyl radicals per chain, number of oxyl radicals per chain, and number of internal loops. As benchmarking, previously published results from a series of experiments on pulsed irradiation of aqueous poly(N-vinylpyrrolidone) (PVP) solutions are used. The numerical simulations clearly show that the pulsed nature of the radiation must be accounted for. The simulations qualitatively reproduce the experimentally observed impact of initial gas saturation (air and N2O) and polymer concentration on the molecular chain length upon irradiation. The formation of double bonds as a function of dose as well as the impact of effective dose rate on the final chain length are also qualitatively reproduced in the simulations.

  • 215.
    Dai, Jing
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Adsorption, aggregation and phase separation in colloidal systems2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The thesis presents work regarding amphiphilic molecules associated in aqueous solution or at the liquid/solid interface. Two main topics are included: the temperature-dependent behavior of micelles and the adsorption of dispersants on carbon nanotube (CNT) surfaces. Various NMR methods were used to analyze those systems, such as chemical shift detection, spectral intensity measurements, spin relaxation and, in particular, self-diffusion experiments. Besides this, small angle X-ray scattering (SAXS) was also applied for structural characterization.

     

    A particular form of phase transition, core freezing, was detected as a function of temperature in micelles composed by a single sort of Brij-type surfactants. In mixed micelles, that phase transition still occurs accompanied by a reversible segregation of different surfactants into distinct aggregates. Adding a hydrophobic solubilizate shifts the core freezing point to a lower temperature. Upon lowering the temperature to the core freezing point, the solubilizate is released. The temperature course of the release curves with different initial solubilizate loadings is rationalized in terms of a temperature-dependent loading capacity.

     

    The behavior of amphiphilic dispersant molecules in aqueous dispersions of carbon nanotubes (CNTs) has been investigated with a Pluronic-type block copolymer as frequent model dispersant. Detailed dispersion curves were recorded and the distribution of the dispersant among different available environments was analyzed. The amount of dispersed CNT was shown to be defined by a complex interplay of several factors during the dispersion process such as dispersant concentration, sonication time, centrifugation and CNT loading. In the dispersion process, high amphiphilic concentration is required because the pristine CNT surfaces made available by sonication must be rapidly covered by dispersants to avoid their re-attachment. In the prepared dispersions, the competitive adsorption of possible dispersants was investigated that provided information about the relative strength of the interaction of those with the nanotube surfaces. Anionic surfactants were found to have a strong tendency to replace Pluronics, which indicates a strong binding of those surfactants.

     

    CNTs were dispersed in an epoxy resin to prepare nanotube-polymer composites. The molecular mobility of epoxy was investigated and the results demonstrated the presence of loosely associated CNT aggregates within which the molecular transport of epoxy is slow because of strong attractive intermolecular interactions between epoxy and the CNT surface. The rheological behavior is dominated by aggregate-aggregate jamming.

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  • 216.
    Dai, Jing
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Alaei, Zahra
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Plazzotta, Beatrice
    Pedersen, Jan Skov
    Furo, Istvan
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Release of Solubilizate from Micelle upon Core Freezing2017In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 121, no 45, p. 10353-10363Article in journal (Refereed)
    Abstract [en]

    By combining NMR (yielding H-1 chemical shift, spin relaxation, and self-diffusion data) and small-angle X-ray scattering experiments, we investigate the complex temperature dependence of the molecular and aggregate states in aqueous solutions of the surfactant [CH3(CH2)(17)(OCH2CH2)(20)OH], abbreviated as C18E20, and.hexamethyldisiloxane, HMDSO. The latter molecule serves as a model for hydrophobic solubilizates. Previously, the pure micellar solution was demonstrated to exhibit core freezing at approximately 7-8 degrees C. At room temperature, we find that HMDSO solubilizes at a volume fraction of approximately 10% in the core of the C18E20 micelles, which consists of molten and thereby highly mobile alkyl chains. Upon lowering the temperature, core freezing is found, just like in pure micelles, but at a temperature shifted significantly to 3 degrees C. The frozen cores contain immobile alkyl chains and exhibit a higher density but are essentially devoid (volume fraction below 1%) of the solubilizate. The latter molecules are released, first gradually and then rather steeply, from the core in the temperature range that is roughly delimited by the two core freezing temperatures, one for pure micelles and one for micelles with solubilizates. The release behavior of systems with different initial HMDSO loading follows the same master curve. This feature is rationalized in terms of loading capacity being strongly temperature dependent: upon lowering the temperature, release commences once the loading capacity descends below the actual solubilizate content. The sharp release curves and the actual release mechanism with its molecular features shown in rich detail have some bearing on a diverse class of possible applications.

  • 217.
    Dai, Jing
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Ferreira Fernandes, Ricardo Manuel
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Regev, Oren
    Marques, Eduardo
    Furo, Istvan
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    The dispersion process of carbon nanotubes sonicated in aqueous solutions of a dispersantManuscript (preprint) (Other academic)
    Abstract [en]

    Single-walled carbon nanotube (SWNT) dispersions are created by sonicating pristine SWNT powders added to aqueous solutions of the dispersant block copolymer Pluronic F127. In those dispersions, the amount of the dispersed SWNT is determined by the combination of TGA and UV-Vis methods, while the dispersant concentration is estimated by 1H NMR spectroscopy. In addition, the amount of dispersant adsorbed at the SWNT surface is obtained by 1H NMR diffusion experiments. A part of the dispersant is taken up by non-dispersed and precipitated particles. Dispersion curves recording the amount of the dispersed SWNT as a function of either the initial dispersant concentration or the final dispersant concentration are obtained at different initial SWNT loadings and sonication times. The results show in detail the way the original SWNT particles are divided into smaller and smaller sizes thereby increasing the available SWNT surface to be covered by dispersant. Centrifugation sets the size-threshold above which SWNT particles are retained in the dispersion which determined the SWNT content as a function of sonication time.

  • 218.
    Damiati, Samar
    KTH.
    In Situ Microfluidic Preparation and Solidification of Alginate Microgels2020In: Macromolecular Research, ISSN 1598-5032, E-ISSN 2092-7673Article in journal (Refereed)
    Abstract [en]

    Biomimetic fabrication of alginate beads has promising applications in the field of synthetic bioarchitecture. Combining microfluidic technology with in situ gelation enables the creation of alginate microgels with precisely tunable size, as well as allowing control of the crosslinking process. Owing to the wide range of applications of alginate microgel beads, this study aimed to develop various microfluidic models for the generation of such beads by investigating the influence of several parameters on their morphologies and dispersity. Four types of glass microfluidic chips with flow focusing or co-flowing droplet generators were used to continuously form alginate droplets, with the possibility of either internal or external alginate gelation by a cross-linking agent supplied by a microfluidic channel. In all four models, alginate was used at a fixed concentration, Span 80 was used as a surfactant to improve the long-term stability of the beads, either mineral oil or oleic acid was used as a continuous phase, and either calcium carbonate (CaCO3) or calcium chloride (CaCl2) was used as a crosslinking agent. The generated beads exhibited various architectures, including individual monodisperse or polydisperse beads, small clusters, and multicompartment systems. The results of the study revealed the importance of microfluidic design and gelation strategy for the generation of stable polymeric architectures. The current study proposes a simple user’s guide to create alginate microgels in various architectures. The fabricated biomimetic models in the form of polymeric-based vesicles can be further exploited in several applications, including cell-like structures, tissue engineering, and cell and drug encapsulation. Additional investigations will be needed, however, to improve these models so that they more closely resemble the natural structures of cells and tissues. [Figure not available: see fulltext.]. 

  • 219. Das, Suman
    et al.
    Dutta, Dipak
    Araujo, Rafael B.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    Chakraborty, Sudip
    Ahuja, Rajeev
    Bhattacharyy, Aninda J.
    Probing the pseudo-1-D ion diffusion in lithium titanium niobate anode for Li-ion battery2016In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 18, no 32, p. 22323-22330Article in journal (Refereed)
    Abstract [en]

    Comprehensive understanding of the charge transport mechanism in the intrinsic structure of an electrode material is essential in accounting for its electrochemical performance. We present here systematic experimental and theoretical investigations of Li+-ion diffusion in a novel layered material, viz. lithium titanium niobate. Lithium titanium niobate (exact composition Li0.55K0.45TiNbO5 center dot 1.06H(2)O) is obtained from sol-gel synthesized potassium titanium niobate (KTiNbO5) by an ion-exchange method. The Li+-ions are inserted and de-inserted preferentially into the galleries between the octahedral layers formed by edge and corner sharing TiO6 and NbO6 octahedral units and the effective chemical diffusion coefficient, is estimated to be 3.8 x 10(-11) cm(2) s(-1) using the galvanostatic intermittent titration technique (GITT). Calculations based on density functional theory (DFT) strongly confirm the anisotropic Li+-ion diffusion in the interlayer galleries and that Li+-ions predominantly diffuse along the crystallographic b-direction. The preferential Li+-ion diffusion along the b-direction is assisted by line-defects, which are observed to be higher in concentration along the b-direction compared to the a-and c-directions, as revealed by high resolution electron microscopy. The Li-Ti niobate can be cycled to low voltages (approximate to 0.2 V) and show stable and satisfactory battery performance over 100 cycles. Due to the possibility of cycling to low voltages, cyclic voltammetry and X-ray photoelectron spectroscopy convincingly reveal the reversibility of Ti3+ <-> Ti2+ along with Ti4+ <-> Ti3+ and Nb5+ <-> Nb4+.

  • 220. Davidsson, Kent O.
    et al.
    Engvall, Klas
    Hagström, Magnus
    Korsgren, John G.
    Lönn, Benny
    Pettersson, Jan B. C.
    A surface ionization instrument for on-line measurements of alkali metal components in combustion: Instrument description and applications2002In: Energy and Fuels, Vol. 16, no 6, p. 1369-1377Article in journal (Refereed)
  • 221.
    Davidsson, Sofia
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering.
    Fogelberg, Viktor
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering.
    Söderqvist, Lovisa
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering.
    Tang, Sofia
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering.
    Change of surfactant for emulsion systems2024Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Nonyfenoletoxylater tillhör en grupp av ickejoniska tensider, vars nedbrytningsprodukt nonylfenol kan bioackumuleras i miljön och har långtgående negativa effekter på vattenlevande organismer. Nonylfenoler har även reproduktiv påverkan och klassas som hormonstörande. Projektet syftar därför till att ersätta nonylfenoletyoxylater mot ett säkrare och miljövänligare alterantiv inom kursen KD2350 Ytor, kolloider och mjuka material. Ytterligare bedöms olika lösningsmedels lämplighet.

    Analysmetoder inkluderade dropptest, DLS, och visuell granskning av emulsionssystemen. Laborationer med ickejonisk tensid utfördes med varierande koncentrationer av lösningmedel, samtensider, etoxyleringsgrad, tensidhalt och salthalt för att skapa önskade emulsionssystem.

    Resultaten visar att det är möjligt att ersätta etoxylerade nonylfenoler med en mindre skadlig tensid. Tensiderna beter sig dock olika och det är inte möjligt att ersätta en nonylfenol med en etoxylerad alkohol med samma etoxyleringsgrad rakt av. De slutliga erhållna emulsionssystemen var transparenta, men var mycket känsliga för temperatur.

    Resultaten som erhölls från projektets laborationer visar dock avvikelser från den teori som finns. Ett exempel är att flera källor skriver att ickejoniska tensider till skillnad från joniska tensider inte kräver en samtensid. Utifrån försöken bildades det inte en mikroemulsion när ingen samtensid i form av alkohol tillsattes till de ickejoniska emulsionerna. Försöket utfördes däremot endast på två tensider med etoxyleringsgrad 8 och 10. Det är möjligt att tensiderna med högre etoxyleringsgrader kan bilda mikroemulsioner utan tillsats av en samtensid.

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  • 222. Davoodi, Ali
    et al.
    Pan, Jinshan
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Leygraf, Christofer
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Parvizi, Reza
    Minuscule device for hydrogen generation/electrical energy collection system on aluminum alloy surface2011In: International journal of hydrogen energy, ISSN 0360-3199, E-ISSN 1879-3487, Vol. 36, no 4, p. 2855-2859Article in journal (Refereed)
    Abstract [en]

    Cogeneration of hydrogen and electrical energy in a single system is still a challenging issue. In this work, in a micro scale, a novel miniaturized system is introduced to capture the electrical energy of produced hydrogen on aluminum alloy by using an ultra-microelectrode based on scanning electrochemical microscopy (SECM). Sophisticated nanosize atomic force microscopy (AFM) based SECM probe could collect the electrochemical current close proximity distance from the aluminum surface to attain the highest possible current efficiency. Various collected current levels were associated to the aluminum microstructure constituents. It is expected that future development in instrumentation could principally facilitate SECM as a tool for hydrogen economy.

  • 223. de Almeida, Katia Júlia
    et al.
    Ramalho, T. C.
    Rinkevicius, Zilvinas
    KTH, School of Biotechnology (BIO), Theoretical Chemistry.
    Vahtras, Olav
    KTH, School of Biotechnology (BIO), Theoretical Chemistry.
    Ågren, Hans
    KTH, School of Biotechnology (BIO), Theoretical Chemistry.
    Cesar, Amary
    Theoretical Study of Specific Solvent Effects on the Optical and Magnetic Properties of Copper(II) Acetylacetonate2011In: Journal of Physical Chemistry A, ISSN 1089-5639, E-ISSN 1520-5215, Vol. 115, no 8, p. 1331-1339Article in journal (Refereed)
    Abstract [en]

    Specific and basicity solvent effects on the visible near-infrared electronic transitions and the electron paramagnetic resonance (EPR) parameters of the copper(II) acetylacetonate complex, Cu(acac)(2), have been investigated at the density functional theory level. The computed absorption transitions as well as the EPR parameters show a strong dependence on the direct coordination environment around the Cu(II) complex. High solvatocromic shifts are observed for 3d-3d transitions, with the highest effect observed for the d(z2)-->d(xy) transition, which is red-shifted by 6000 cm(-1) and 9000 cm(-1) in water and pyridine solvent models, respectively. Compared to the electronic g-tensors, the hyperfine coupling constants of the Cu(acac)(2) complex show a more pronounced dependence on the effect of base strength of solvent. Overall, the present methodology satisfactorily models the solvent effect on the optical and magnetic properties of the Cu(acac)(2) complex, and theory and experiment agree sufficiently well to warrant the use of the computed optical and EPR parameters to elucidate the coordination environment of the Cu(II) systems in basic solutions.

  • 224.
    de Almeida, Katia Júlia
    et al.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry.
    Rinkevicius, Zilvinas
    KTH, School of Biotechnology (BIO), Theoretical Chemistry.
    Vahtras, Olav
    KTH, School of Biotechnology (BIO), Theoretical Chemistry.
    Cesar, Amary
    Universidade Federal de Minas Gerais, Departamento de Química.
    Ågren, Hans
    KTH, School of Biotechnology (BIO), Theoretical Chemistry.
    Theoretical study of specific solvent effects on the optical and magnetic properties of copper(II) acetylacetonateManuscript (Other academic)
  • 225.
    Dedinaite, Andra
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Surface and Corrosion Science.
    Claesson, Per M.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Surface and Corrosion Science.
    How synergistic aqueous lubrication is mediated by natural and synthetic molecular aggregates2019In: IOP Conference Series: Materials Science and Engineering, Institute of Physics Publishing , 2019, no 1Conference paper (Refereed)
    Abstract [en]

    Nature lubricates in aqueous environment, and thus the example of a human synovial joint with its seamless function has been a fascination for scientists since the times of the birth of modern science. Here, inspired by nature, we investigate the mechanistic function of three different types of synergistic molecular aggregates. Firstly, we show how simple phospholipids lubricate hydrophilic model surfaces of silica and how this lubrication is facilitated further by the presence of an anionic polysaccharide, hyaluronan, due to the enhanced surface build-up of lubricant material. Next, we mimic natural polylectrolytesurfactant aggregation by employing a highly positively charged polyelectrolyte and anionic surfactant that strongly associate both in the bulk and at the surfaces by building structured aggregates that lubricate due to hydration lubrication. This occurs despite of the presence of strong attraction between the lubricated surfaces. This is an example of synergistic lubrication due to particular internal structural arrangement of the aggregates. Finally, we investigate the case of synergistic lubrication due to preferential surface ordering of two biological polyelectrolytes, cartilage oligomeric matrix protein and lubricin, that leads to favourable lubrication.

  • 226.
    Dedinaite, Andra
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Pettersson, Torbjörn
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Mohanty, Biswaranjan
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Claesson, Per M
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Lubrication by organized soft matter2010In: SOFT MATTER, ISSN 1744-683X, Vol. 6, no 7, p. 1520-1526Article in journal (Refereed)
    Abstract [en]

    The AFM-colloidal probe technique has been used to explore surface interactions and friction forces between polyelectrolyte-coated surfaces immersed in aqueous solutions in the absence and presence of surfactant. It is found that the nature of the load bearing forces is decisive for the lubricating properties of the layers. Low frictional forces are obtained when the load is carried by a force that allows the interfacial layer to have a high fluidity, whereas attractive surface forces most often increase the friction. Highly charged polyelectrolytes and oppositely charged surfactants associate in bulk solution to form complexes with a well-defined internal structure. At the surface, similarly structured polyelectrolyte-surfactant layers are spontaneously formed. Such layers have a high load bearing capacity, and the friction coefficient is very low as long as the integrity of the layer remains intact. Interestingly, when the load is increased step-wise the friction force as a function of load displays some sharp peaks, which are identified as being due to structural rearrangements in the polyelectrolyte-surfactant layer. On unloading very low frictional forces are obtained despite the presence of an adhesion between the layers. To maintain the favorable lubricating properties it is essential to have surfactants present in solution, whereas, after the initial adsorption step, there is no need to have the polyelectrolyte present in the bulk. The reason for this is the essentially irreversible adsorption of the polyelectrolyte.

  • 227.
    Degeneve, Emilie
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering.
    Filtration of oil-in-water nanoemulsions for potential adjuvant development applications2023Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In this study, innovative compositions for vaccine adjuvant production were investigated. The purpose was to stabilize oil-in-water nanoemulsion, using squalene oil (employed in the pharmaceutical industry), with different surfactants and test the filterability of these nanoemulsions. Particles around 160 nm, size of the particle in the pharmaceutical industry, and below were aimed. 

    Classical surfactants, polyoxyethylene sorbitan monooleate (Tween 80) and sorbitan trioleate (Span 85) were first tested to stabilize the squalene oil emulsion. Then, two grades of polyvinyl alcohol, PVA 4-88 (88% hydrolyse) and PVA 4-98 (98% hydrolyse), were employed. To produce the nanoemulsions, high-energy and self-emulsion methods were performed. To investigate the filterability of the emulsions, the products were filtrated through cellulose acetate disc membranes of 0.2 µm cut-off size in dead-end mode and the flow rate was followed gravimetrically. The classical combination Tween 80 and Span 85 produced particles under the cut-off size of the filter. Span 85 and Tween 80, each combined with PVA 4-88, showed that Span 85 and PVA 4-88 do not stabilise properly the nanoemulsions leading to the obtention of big particles (above 200 nm). However, the combination of Tween 80 and PVA 4-88 was able to stabilise very small particles of squalene oil (under 10 nm) as well as the combination PVA 4-88 and PVA 4-98 which successfully produced particles around 10 nm. The filterability tests showed that high squalene oil content would deteriorate the filterability of the emulsions involving Tween 80 and/or Span 85 and that high amounts of PVA 4-88, when combined with PVA 4-98, improved the filterability of the emulsions. No issue with high squalene amount was noticed for the PVA 4-88/PVA 4-98 combination.

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  • 228.
    Delcey, Mickael G
    et al.
    Department of Chemistry - Ångström Laboratory, Uppsala University, SE-75120 Uppsala, Sweden.
    Lindblad, Rebecka
    Department of Physics, Lund University, Box 118, SE-22100 Lund, Sweden;Abteilung für Hochempfindliche Röntgenspektroskopie, Helmholtz-Zentrum Berlin für Materialien und Energie, Albert-Einstein-Str. 15, 12489 Berlin, Germany;Inorganic Chemistry, Department of Chemistry - Ångström Laboratory, Uppsala University, SE-75121 Uppsala, Sweden.
    Timm, Martin
    Abteilung für Hochempfindliche Röntgenspektroskopie, Helmholtz-Zentrum Berlin für Materialien und Energie, Albert-Einstein-Str. 15, 12489 Berlin, Germany;Institut für Optik und Atomare Physik, Technische Universität Berlin, Hardenbergstr. 36, 10623 Berlin, Germany.
    Bülow, Christine
    Abteilung für Hochempfindliche Röntgenspektroskopie, Helmholtz-Zentrum Berlin für Materialien und Energie, Albert-Einstein-Str. 15, 12489 Berlin, Germany;Physikalisches Institut, Albert-Ludwigs-Universität Freiburg, Hermann-Herder-Str. 3, 79104, Freiburg, Germany.
    Zamudio-Bayer, Vicente
    Abteilung für Hochempfindliche Röntgenspektroskopie, Helmholtz-Zentrum Berlin für Materialien und Energie, Albert-Einstein-Str. 15, 12489 Berlin, Germany.
    von Issendorff, Bernd
    Physikalisches Institut, Albert-Ludwigs-Universität Freiburg, Hermann-Herder-Str. 3, 79104, Freiburg, Germany.
    Lau, J. Tobias
    Abteilung für Hochempfindliche Röntgenspektroskopie, Helmholtz-Zentrum Berlin für Materialien und Energie, Albert-Einstein-Str. 15, 12489 Berlin, Germany;Physikalisches Institut, Albert-Ludwigs-Universität Freiburg, Hermann-Herder-Str. 3, 79104, Freiburg, Germany.
    Lundberg, Marcus
    Department of Chemistry - Ångström Laboratory, Uppsala University, SE-75120 Uppsala, Sweden.
    Soft X-ray signatures of cationic manganese–oxo systems, including a high-spin manganese(v) complex2022In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 24, no 6, p. 3598-3610Article in journal (Refereed)
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  • 229.
    Delin, Anna
    et al.
    KTH, Superseded Departments (pre-2005), Materials Science and Engineering.
    Tosatti, E
    Emerging magnetism in platinum nanowires2004In: Surface Science, ISSN 0039-6028, E-ISSN 1879-2758, Vol. 566, p. 262-267Article in journal (Refereed)
    Abstract [en]

    We have investigated infinitely long, monostrand Pt nanowires theoretically, and found that they exhibit Hund's rule magnetism. We find a spin moment of 0.6 mu(B) per atom, at the equilibrium bond length. Its magnetic moment increases with stretching. The origin of the wire magnetism is analyzed and its effect on the conductance through the wire is discussed.

  • 230.
    Deng, Tengfei
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Micro-Modelling.
    Du, Sichen
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Micro-Modelling.
    Study of Lime Dissolution Under Forced Convection2012In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 43, no 3, p. 578-586Article in journal (Refereed)
    Abstract [en]

    Dissolution of different CaO cubes under force convection in liquid CaO-"FeO"-SiO2 slag was studied at 1873 K (1600 A degrees C). A linear relationship between normalized lengths and time was obtained after the experiment. It was evidently observed that the removal of the interface layer(s) including 2CaO center dot SiO2 by shear stress was the main mechanism for the dissolution. A stirring rate of approximately 100 rpm was found to be efficient to remove the interface layer(s). The limes with different structures had different dissolution rates.

  • 231.
    Deng, Zijian
    et al.
    Dalian Univ Technol DUT, State Key Lab Fine Chem, Inst Artificial Photosynth, Dalian 116024, Peoples R China..
    Yang, Xichuan
    Dalian Univ Technol DUT, State Key Lab Fine Chem, Inst Artificial Photosynth, Dalian 116024, Peoples R China..
    Yang, Kaiyuan
    Dalian Univ Technol DUT, State Key Lab Fine Chem, Inst Artificial Photosynth, Dalian 116024, Peoples R China..
    Zhang, Li
    Dalian Univ Technol DUT, State Key Lab Fine Chem, Inst Artificial Photosynth, Dalian 116024, Peoples R China..
    Wang, Haoxin
    Dalian Univ Technol DUT, State Key Lab Fine Chem, Inst Artificial Photosynth, Dalian 116024, Peoples R China..
    Wang, Xiuna
    Dalian Univ Technol DUT, State Key Lab Fine Chem, Inst Artificial Photosynth, Dalian 116024, Peoples R China..
    Sun, Licheng
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Organic chemistry. Dalian Univ Technol DUT, State Key Lab Fine Chem, Inst Artificial Photosynth, Dalian 116024, Peoples R China.;Westlake Univ, Ctr Artificial Photosynth Solar Fuels, Sch Sci, Hangzhou 310024, Peoples R China..
    Helical Copper Redox Mediator with Low Electron Recombination for Dye-Sensitized Solar Cells2021In: ACS Sustainable Chemistry and Engineering, E-ISSN 2168-0485, Vol. 9, no 15, p. 5252-5259Article in journal (Refereed)
    Abstract [en]

    Redox mediators play a major role in determining the photocurrent and photovoltage in dye-sensitized solar cells (DSSCs). Copper complexes are a good option for redox mediators but suffer from electron recombination. The traditional method is to add 4-(tert-butyl)pyridine (TBP) to the electrolyte, which is coordinated with the empty orbit of Ti, thereby slowing down the oxidized mediator's ability to capture electrons. However, this strategy will result in competitive coordination between the redox mediator and TBP, decreasing the stability of the device. In this study, two helical copper(I) complexes are synthesized and applied to TBP-free solar cells. La (1,3-bis(2,2'-bipyridin-6-yloxy)propane) and Lb (1,3-bis[(6'-methyl-2,2'-bipyridin-6-yl)oxy]propane) tend to form double-stranded helicates ([Cu-2(Ln)(2)](2+), n = a, b) rather than mononuclear complexes ([Cu(Ln)](+), n = a, b). To facilitate quantitative analysis of the complexes, Cu(I)Ln and Cu(II)Ln (n = a, b) are used as molecular formulae. (CuLa)-La-I and Cu(I)Lb are characterized by electrospray mass spectroscopy, H-1 NMR spectroscopy, and electrochemistry. J-V measurement shows that both V-oc and J(sc) increase with the increase of (CuLa)-La-I concentration (below 0.1 M), and the best power conversion efficiency is 8.2%. The relationship between Cu(I) concentration and recombination for further study was measured by IMVS.

  • 232.
    Denisov, Nikita
    et al.
    Department of Materials Science and Engineering, Chair for Surface Science and Corrosion (WW4-LKO), Friedrich-Alexander-Universität Erlangen-Nürnberg, Martensstrasse 7, 91058, Erlangen, Germany, Martensstrasse 7.
    Qin, Shanshan
    Department of Materials Science and Engineering, Chair for Surface Science and Corrosion (WW4-LKO), Friedrich-Alexander-Universität Erlangen-Nürnberg, Martensstrasse 7, 91058, Erlangen, Germany, Martensstrasse 7.
    Will, Johannes
    Institute of Micro- and Nanostructure Research & Center for Nanoanalysis and Electron Microscopy (CENEM), IZNF, Friedrich-Alexander-Universität Erlangen-Nürnberg, Cauerstraße 3, 91058, Erlangen, Germany, Cauerstraße 3.
    Vasiljevic, Bojana Nedić
    Faculty of Physical Chemistry, University of Belgrade, Studentski trg 12-16, Belgrade, 11000, Serbia, Studentski trg 12-16.
    Skorodumova, Natalia
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Structures.
    Pašti, Igor
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Structures. Faculty of Physical Chemistry, University of Belgrade, Studentski trg 12-16, Belgrade, 11000, Serbia, Studentski trg 12-16.
    Sarma, Bidyut Bikash
    Institute of Catalysis Research and Technology and Institute for Chemical Technology and Polymer Chemistry, Karlsruhe Institute of Technology, 76131, Karlsruhe, Germany.
    Osuagwu, Benedict
    Department of Materials Science and Engineering, Chair for Surface Science and Corrosion (WW4-LKO), Friedrich-Alexander-Universität Erlangen-Nürnberg, Martensstrasse 7, 91058, Erlangen, Germany, Martensstrasse 7.
    Yokosawa, Tadahiro
    Institute of Micro- and Nanostructure Research & Center for Nanoanalysis and Electron Microscopy (CENEM), IZNF, Friedrich-Alexander-Universität Erlangen-Nürnberg, Cauerstraße 3, 91058, Erlangen, Germany, Cauerstraße 3.
    Voss, Johannes
    Institute of Micro- and Nanostructure Research & Center for Nanoanalysis and Electron Microscopy (CENEM), IZNF, Friedrich-Alexander-Universität Erlangen-Nürnberg, Cauerstraße 3, 91058, Erlangen, Germany, Cauerstraße 3.
    Wirth, Janis
    Institute of Micro- and Nanostructure Research & Center for Nanoanalysis and Electron Microscopy (CENEM), IZNF, Friedrich-Alexander-Universität Erlangen-Nürnberg, Cauerstraße 3, 91058, Erlangen, Germany, Cauerstraße 3.
    Spiecker, Erdmann
    Institute of Micro- and Nanostructure Research & Center for Nanoanalysis and Electron Microscopy (CENEM), IZNF, Friedrich-Alexander-Universität Erlangen-Nürnberg, Cauerstraße 3, 91058, Erlangen, Germany, Cauerstraße 3.
    Schmuki, Patrik
    Department of Materials Science and Engineering, Chair for Surface Science and Corrosion (WW4-LKO), Friedrich-Alexander-Universität Erlangen-Nürnberg, Martensstrasse 7, 91058, Erlangen, Germany, Martensstrasse 7; Regional Centre of Advanced Technologies and Materials, Šlechtitelů 27, Olomouc, 78371, Czech Republic, Šlechtitelů 27; Department of Chemistry, Faculty of Science, King Abdulaziz University, P.O. Box 80203, Jeddah, 21569, Saudi Arabia, P.O. Box 80203.
    Light-Induced Agglomeration of Single-Atom Platinum in Photocatalysis2023In: Advanced Materials, ISSN 0935-9648, E-ISSN 1521-4095, Vol. 35, no 5, article id 2206569Article in journal (Refereed)
    Abstract [en]

    With recent advances in the field of single-atoms (SAs) used in photocatalysis, an unprecedented performance of atomically dispersed co-catalysts has been achieved. However, the stability and agglomeration of SA co-catalysts on the semiconductor surface may represent a critical issue in potential applications. Here, the photoinduced destabilization of Pt SAs on the benchmark photocatalyst, TiO2, is described. In aqueous solutions within illumination timescales ranging from few minutes to several hours, light-induced agglomeration of Pt SAs to ensembles (dimers, multimers) and finally nanoparticles takes place. The kinetics critically depends on the presence of sacrificial hole scavengers and the used light intensity. Density-functional theory calculations attribute the light induced destabilization of the SA Pt species to binding of surface-coordinated Pt with solution-hydrogen (adsorbed H atoms), which consequently weakens the Pt SA bonding to the TiO2 surface. Despite the gradual aggregation of Pt SAs into surface clusters and their overall reduction to metallic state, which involves >90% of Pt SAs, the overall photocatalytic H2 evolution remains virtually unaffected.

  • 233.
    Diesen, Veronica
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Heterogeneous TiO2 Photocatalysis: Fundamental Chemical Aspects and Effects of Solid Phase Alterations2013Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Heterogeneous photocatalysis on TiO2 is an emerging green technology for water disinfection. The rationale for this technology is based on in-situ generation of highly reactive transitory species for degradation of organic and inorganic pollutants as well as microorganisms. Recent research has concentrated on improving the efficiency of the photocatalytic process, however, some fundamental information on the mechanistic aspects and rate limiting properties still remain elusive. 

       The focus of this thesis has been to identify the primary oxidant in heterogeneous TiO2 photocatalysis and to create prerequisites for further evaluation of how selected internal (material specific) and external (system specific) alterations influence the photocatalytic activity. Furthermore, an attempt to induce visible light activity to a modified TiO2 film was also made.

       Production of H2O2 was used to probe the existence of the hydroxyl radical as the primary oxidizing species in aqueous TiO2 photocatalysis. The only possible pathway to produce H2O2 in an oxygen free environment is through hydroxyl radical recombination. A significant amount of H2O2 could be detected in deoxygenated solutions confirming the existence of hydroxyl radicals. To further elucidate the origin of the H2O2, experiments with the hydroxyl radical scavenger Tris(hydroxymethyl)aminomethane (Tris) were performed. The results further support the hypothesis that the hydroxyl radical is the primary oxidant in TiO2 photocatalysis.

       Tris was evaluated as a probe in aqueous photocatalysis. Hydrogen abstracting species such as hydroxyl radicals are able to abstract hydrogen atoms from Tris, which leads to formation of formaldehyde. Formaldehyde was detected and quantified by a modified version of the Hantzsch reaction. This route to probe the photocatalytic efficiency allows for assessment of the maximum photocatalytic efficiency with high accuracy and sensitivity and was further used to study how selected solid phase alterations and dissolved electron acceptors affect the photocatalytic efficiency. The results showed that the surface area of immobilized photocatalysts affects the efficiency and a high surface area is advantageous for photocatalysis. It was also shown that TiO2 enhanced with Ag nanoparticles significantly increases photocatalytic activity. This is explained partly by an increased O2 adsorption and reduction process on the Ag enhanced TiO2 compared to pure TiO2 and partly as a Schottky barrier formation at the metal-semiconductor interface. These processes lead to a prolonged charge separation in the photocatalyst, which is advantageous for the efficiency. Moreover, the effect of the external, dissolved electron acceptors H2O2 and O2 were also evaluated by Tris. The results showed an increased photocatalytic activity upon addition of the electron acceptors. It was also shown that the adsorption affinity of a reactant to the photocatalyst is rate controlling and governs the kinetics.

       An attempt to induce visible light activity into a TiO2 film was also made by a post-treatment in liquid NH3. The slightly narrowed bandgap of the resulting film caused a red-shift in the absorption band and the film showed visible light activity under illumination by white light with a cut-off filter at 385 nm.

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  • 234. Dixit, M.
    et al.
    Maark, T. A.
    Ghatak, K.
    Ahuja, Rajeev
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    Pal, S.
    Scandium-decorated MOF-5 as potential candidates for room-temperature hydrogen storage: A solution for the clustering problem in MOFs2012In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 116, no 33, p. 17336-17342Article in journal (Refereed)
    Abstract [en]

    Transition-metal-based systems show promising binding energy for hydrogen storage but suffer from clustering problem. The effect of light transition metal (M = Sc, Ti) decoration, boron substitution on the hydrogen storage properties of MOF-5, and clustering problem of metals has been investigated using ab initio density functional theory. Our results of solid-tate calculations reveal that whereas Ti clusters strongly Sc atoms do not suffer from this problem when decorating MOF-5. Boron substitution on metal-decorated MOF-5 enhances the interaction energy of both the metals with MOF-5. Sc-decorated MOF-5 shows a hydrogen storage capacity of 5.81 wt % with calculated binding energies of 20-40 kJ/mol, which ensures the room-temperature applicability of this hydrogen storage material.

  • 235.
    Dobrota, Ana S.
    et al.
    Univ Belgrade, Fac Phys Chem, Studentski Trg 12-16, Belgrade 11000, Serbia..
    Dokic, Tanja
    Univ Belgrade, Fac Phys Chem, Studentski Trg 12-16, Belgrade 11000, Serbia..
    Skorodumova, Natalia
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Mentus, Slavko V.
    Univ Belgrade, Fac Phys Chem, Studentski Trg 12-16, Belgrade 11000, Serbia.;Serbian Acad Arts & Sci, Knez Mihajlova 35, Belgrade 11000, Serbia..
    Pašti, Igor
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering. Univ Belgrade, Fac Phys Chem, Studentski Trg 12-16, Belgrade 11000, Serbia..
    What Is the Real State of Single-Atom Catalysts under Electrochemical Conditions-From Adsorption to Surface Pourbaix Plots?2021In: Catalysts, E-ISSN 2073-4344, Vol. 11, no 10, article id 1207Article in journal (Refereed)
    Abstract [en]

    The interest in single-atom catalysts (SACs) is increasing, as these materials have the ultimate level of catalyst utilization, while novel reactions where SACs are used are constantly being discovered. However, to properly understand SACs and to further improve these materials, it is necessary to consider the nature of active sites under operating conditions. This is particularly important when SACs are used as electrocatalysts due to harsh experimental conditions, including extreme pH values or high anodic and cathodic potential. In this contribution, density functional theory-based thermodynamic modelling is used to address the nature of metal centers in SACs formed by embedding single metal atoms (Ru, Rh, Ir, Ni, Pd, Pt, Cu, Ag, and Au) into graphene monovacancy. Our results suggest that none of these SAC metal centers are clean at any potential or pH in the water thermodynamic stability region. Instead, metal centers are covered with H-ads, OHads, or O-ads, and in some cases, we observed the restructuring of the metal sites due to oxygen incorporation. Based on these findings, it is suggested that setting up theoretical models for SAC modelling and the interpretation of ex situ characterization results using ultra-high vacuum (UHV) techniques requires special care, as the nature of SAC active sites under operating conditions can significantly diverge from the basic models or the pictures set by the UHV measurements.

  • 236.
    Dobrota, Ana S.
    et al.
    Univ Belgrade, Fac Phys Chem, Studentski Trg 12-16, Belgrade 11158, Serbia..
    Vlahovic, Jovana
    Univ Belgrade, Fac Phys Chem, Studentski Trg 12-16, Belgrade 11158, Serbia.;Univ Antwerp, Dept Phys, Groenenborgerlaan 171, B-2020 Antwerp, Belgium..
    Skorodumova, Natalia
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Pašti, Igor
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering. Univ Belgrade, Fac Phys Chem, Studentski Trg 12-16, Belgrade 11158, Serbia..
    First-principles analysis of aluminium interaction with nitrogen-doped graphene nanoribbons: From adatom bonding to various2022In: Materials Today Communications, ISSN 2352-4928, Vol. 31, article id 103388Article in journal (Refereed)
    Abstract [en]

    Enhancing aluminium interaction with graphene-based materials is of crucial importance for the development of Al-storage materials and novel functional materials via atomically precise doping. Here, DFT calculations are employed to investigate Al interactions with non-doped and N-doped graphene nanoribbons (GNRs) and address the impact of the edge sites and N-containing defects on the material's reactivity towards Al. The presence of edges does not influence the energetics of Al adsorption significantly (compared to pristine graphene sheet). On the other hand, N-doping of graphene nanoribbons is found to affect the adsorption energy of Al to an extent that strongly depends on the type of N-containing defect. The introduction of edge-NO group and doping with in -plane pyridinic N result in Al adsorption nearly twice as strong as on pristine graphene. Moreover, double n-type doping via N and Al significantly alters the electronic structure of Al,N-containing GNRs. Our results suggest that selectively doped GNRs with pyridinic N can have enhanced Al-storage capacity and could be potentially used for selective Al electrosorption and removal. On the other hand, Al,N-containing GNRs with pyridinic N could also be used in resistive sensors for mechanical deformation. Namely, strain along the longitudinal axis of these dual doped GNRs does not affect the binding of Al but tunes the bandgap and causes more than 700-fold change in the conductivity. Thus, careful defect engineering and selective doping of GNRs with N (and Al) could lead to novel multifunctional materials with exceptional properties. [GRAPHICS]

  • 237. Dobryden, Illia
    et al.
    Steponaviciute, Medeina
    Vilnius Univ, Inst Chem, LT-03225 Vilnius, Lithuania..
    Hedman, Daniel
    Luleå Univ Technol, Dept Engn Sci & Math, Div Mat Sci, Appl Phys, SE-97187 Luleå, Sweden.;Inst Basic Sci IBS, Ctr Multidimens Carbon Mat, Ulsan 44919, South Korea..
    Klimkevicius, Vaidas
    Vilnius Univ, Inst Chem, LT-03225 Vilnius, Lithuania..
    Makuska, Ricardas
    Vilnius Univ, Inst Chem, LT-03225 Vilnius, Lithuania..
    Dédinaité, Andra
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Engineering Pedagogics. RISE Res Inst Sweden, Div Biosci & Mat, SE-11486 Stockholm, Sweden..
    Liu, Xiaoyan
    Shaanxi Normal Univ, Sch Chem & Chem Engn, Xian 710062, Peoples R China..
    Corkery, Robert W.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Surface and Corrosion Science.
    Claesson, Per M.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Surface and Corrosion Science.
    Local Wear of Catechol-Containing Diblock Copolymer Layers: Wear Volume, Stick-Slip, and Nanomechanical Changes2021In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 125, no 38, p. 21277-21292Article in journal (Refereed)
    Abstract [en]

    Polymers containing catechol groups have gained a large interest, as they mimic an essential feature of mussel adhesive proteins that allow strong binding to a large variety of surfaces under water. This feature has made this class of polymers interesting for surface modification purposes, as layer functionalities can be introduced by a simple adsorption process, where the catechol groups should provide a strong anchoring to the surface. In this work, we utilize an AFM-based method to evaluate the wear resistance of such polymer layers in water and compare it with that offered by electrostatically driven adsorption. We pay particular attention to two block copolymer systems where the anchoring group in one case is an uncharged catechol-containing block and in the other case a positively charged and catechol-containing block. The wear resistance is evaluated in terms of wear volume, and here, we compare with data for similar copolymers with statistical distribution of the catechol groups. Monitoring of nanomechanical properties provides an alternative way of illustrating the effect of wear, and we use modeling to show that the stiffness, as probed by an AFM tip, of the soft layer residing on a hard substrate increases as the thickness of the layer decreases. The stick-slip characteristics are also evaluated.

  • 238.
    Dobryden, Illia
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Surface and Corrosion Science.
    Tokarski, Tomasz
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Surface and Corrosion Science.
    Cortes Ruiz, M.
    Li, Gen
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Surface and Corrosion Science.
    Claesson, Per M.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Surface and Corrosion Science. RISE Research Institutes of Sweden, Division of Bioscience and Materials, Stockholm, Sweden.
    Nanoscale mapping of interphase with AFM: Polymer based nanocomposites2019In: Baltic Polymer Symposium 2019, BPS 2019 - Programme and Proceedings, Institute of Chemistry and Geosciences, Vilnius University , 2019Conference paper (Refereed)
  • 239.
    Dobryden, Illia
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Surface and Corrosion Science.
    Yang, Z.
    Claesson, Per M.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Surface and Corrosion Science.
    Pileni, M. P.
    Water Dispersive Suprastructures: An Organizational Impact on Nanomechanical Properties2021In: Advanced Materials Interfaces, ISSN 2196-7350, Vol. 8, no 3, article id 2001687Article in journal (Refereed)
    Abstract [en]

    Water dispersive 2D and 3D suprastructures offer a large number of potential applications in energy release, biomedicine and other fields. The nanomechanical properties of two suprastructures of self-assembled 9.6 nm Fe3O4 hydrophobic nanocrystals dispersed in water are elucidated by using atomic force microscopy. These suprastructures are either a shell consisting of a few layers of nanocrystals or spherical self-assemblies of nanocrystals in fcc superlattices called colloidosomes and supraballs, respectively. The major difference in the preparation of these suprastructure is based on the presence or not of octadecene molecules. It is recently demonstrated that these structures behave as nanoheaters and remain self-assembled after internalization in cancer cells. The observed differences between these suprastructures in terms of cell sensing are suggested to be related to their mechanical properties, which emphasize the importance of better understanding the nanomechanics of such suprastructures. In this study the nanomechanical properties of these suprastructures are shown to be load-depended in aqueous medium. Colloidosomes demonstrate higher flexibility and deformability than the supraballs. These findings provide essential knowledge for understanding differences in cell internalization and implementation in biomedicine. The differences in nanomechanical properties between these types of suprastructures are mainly due to their structures (hollow core–shell or fcc supracrystals).

  • 240. Doll, Jim
    et al.
    Dupuis, Paul
    Nyquist, Pierre
    Thermodynamic integration methods, infinite swapping and the calculation of generalized averages2017In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 146Article in journal (Refereed)
    Abstract [en]

    In the present paper we examine the risk-sensitive and sampling issues associated with the problem of calculating generalized averages. By combining thermodynamic integration and Stationary Phase Monte Carlo techniques, we develop an approach for such problems and explore its utility for a prototypical class of applications.

  • 241. Dong, Hanwu
    et al.
    Kiros, Yohannes
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Noreus, Dag
    An air-metal hydride battery using MmNi(3.6)Mn(0.4)Al(0.3)Co(0.7) in the anode and a perovskite in the cathode2010In: International journal of hydrogen energy, ISSN 0360-3199, E-ISSN 1879-3487, Vol. 35, no 9, p. 4336-4341Article in journal (Refereed)
    Abstract [en]

    Hydrogen storage alloy MmNi(3.6)Mn(0.4)Al(0.3)Co(0.7) (MH) was tested as anode material in a metal hydride-air cell. The cathode was a non-noble metal air electrode based on a mixture of perovskite and pyrolyzed macrocycles on carbon. Polarization and discharge capacities of the electrodes were measured and compared at 22 degrees C and 40 degrees C using air or oxygen at the cathode. Discharge capacity reaching 330 mAh/g MH with pure oxygen at 40 degrees C and 305 mAh/g MH with air at 22 degrees C were obtained. Power densities and/or energy densities were found to significantly depend on the increase of the electrode kinetics on both the ORR (oxygen reduction reaction) and HOR (hydrogen oxidation reaction). However, for air electrode, an increase of oxygen concentration by using pure oxygen gas plays a more important role than an 18 degrees C temperature increase. (C) 2010 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.

  • 242. Dong, Jingfeng
    et al.
    Wang, Mei
    Zhang, Pan
    Yang, Songqiu
    Liu, Jianyong
    Li, Xueqiang
    Sun, Licheng
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Promoting Effect of Electrostatic Interaction between a Cobalt Catalyst and a Xanthene Dye on Visible-Light-Driven Electron Transfer and Hydrogen Production2011In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 115, no 30, p. 15089-15096Article in journal (Refereed)
    Abstract [en]

    The readily obtained noble-metal-free molecular catalyst systems, with xanthene dyes (Rose Bengal, RB(2-); Eosin Y, EY(2-); and Eosin B, EB(2-)) as photosensitizers, [Co(bpy)(3)]Cl(2) as catalyst, and triethylamine as sacrificial electron donor, are highly active for visible-light-driven (lambda > 450 nm) hydrogen production from water. The turnover frequency is up to 54 TON/min versus RB(2-) with a RB(2-)/[Co(bpy)(3)]Cl(2) molar ratio of 1:10 in CH(3)CN/H(2)O under optimal conditions in the first half hour of irradiation (lambda > 450 rim), and the turnover number is up to 2076 versus RB(2-). Comparative studies show the following: (1) The photocatalytic H(2)-evolving activity of the cationic cobalt complex [Co(bpy)(3)]Cl(2), is apparently higher than the neutral cobaloxime complexes with xanthene dyes as potosensitizers, and also much higher than the analogous system of [Ru(bpy)(3)]Cl(2)/[Co(bpy)(3)]Cl(2). (2) The UV-vis absorptions of xanthene dyes are red shifted to different extents upon addition of [Co(bpy)(3)]Cl(2) to the aqueous or CH(3)CN/H(2)O solutions of these dyes, while no change was observed in UV-vis absorptions of photosensitizer with addition of the cobaloximes to the aqueous solution of RB(2-) or addition of [Co(bpy)(3)]Cl(2) to the aqueous solution of [Ru(bpy)(3)]Cl(2). (3) The fluorescence of RB(2-) is significantly quenched by [Co(bpy)(3)]Cl(2), but not by the cobaloximes. These special performances of [Co(bpy)(3)]Cl(2) are attributed to the electrostatically attractive interaction between the anionic organic dyes and the cationic cobalt catalyst. The probable mechanism for photoinduced hydrogen production catalyzed by the system of RB(2-), [Co(bpy)(3)]Cl(2), and triethylamine is discussed in detail on the basis of fluorescence. fand transient absorption spectroscopic studies. "

  • 243.
    Duan, Sai
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Geometrical and Electronic Structures at Molecule-Metal Interfaces from Theoretical Modeling2012Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    In this thesis, we focus on theoretical investigations on metal interfaces where many heterogeneous chemical reactions take place. Surface-enhanced Raman scattering (SERS) spectroscopy and the modern electrochemical methods are important in-situ techniques that have been widely employed for a variety of applications. Theoretical simulations have become an indispensable tool to infer the molecular details of interfacial structures that are not directly accessible from experimental measurements. In this context, we have proposed several new theoretical models for both SERS and interfacial electrochemistry, which allow us to provide molecular-level understanding of the interfacial structures under the realistic experimental conditions.

     

    The first part of the thesis has addressed the basic theory of SERS that offers the vibrational structure of the interfacial molecules. It is well known that the huge enhancement of Raman intensity in this technique can be attributed to two independent factors, namely the physical and chemical enhancements. The former is resulted from the enhanced electromagnetic field induced by the plasmonic excitations, while the latter comes from the changing of interaction between the molecule and the surface. The interplay between these two enhancement factors, which has long been an issue of debate, is revealed in this thesis. They are coupled through molecular polarizability. A practical computational approach is proposed and used to demonstrate the importance of the coupling on different molecular systems. It is found that for certain systems the coupling factor can be as large as 106. This finding is of great importance towards a comprehensive understanding of the SERS mechanisms and a quantitative prediction of the enhancement factor.

     

    The other part of the thesis is devoted to the theory of interfacial electrochemistry, in particular the effects of water solution. A novel protocol that combines classical molecular dynamics (MD) and the first principles density functional theory (DFT) calculations is proposed to address the statistical behavior of interfacial properties. Special attention has been paid to the work function of Pt(111) surface and CO adsorption energy on Pt(111) surface in aqueous solution. It has been found that in this case the work function of Pt surface illustrates a surprisingly broad distribution under the room temperature, sheds new light on the understanding of reaction activity of the surface. The proposed protocol is able to provide results in very good agreement with experiments and should be applied routinely in future studies.

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  • 244.
    Duan, Sai
    et al.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Ai, Yue-Jie
    Hu, Wei
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Luo, Yi
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Roles of Plasmonic Excitation and Protonation on Photoreactions of p-Aminobenzenethiol on Ag Nanoparticles2014In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 118, no 13, p. 6893-6902Article in journal (Refereed)
    Abstract [en]

    There is increasing evidence that surface plasmons could catalyze photochemical reactions of organic molecules on metal surfaces. However, due to the complex interactions among the substrate, the adsorbate, the environment, and the incident light, the existence and the underlying mechanism of such catalytic processes have been under intense debate. Here we present a systematic first principles study on one of the most studied and controversial systems, namely, p-aminobenzenethiol (PATP) adsorbed on silver nanoparticles. Our calculations have confirmed that the observed surface-enhanced Raman scattering (SERS) bands at 1142, 1391, and 1440 cm(-1) of PATP on silver surfaces belong to its coupling reaction product, 4,4'-dimercaptoazobenzene (DMAB). It is found that the deprotonation or protonation of N atoms is the key initial step for the transformations between PATP and DMAB. The photodecomposition reaction from DMAB to PATP can occur only under the conditions that both proton transfer and plasmonic excitations have taken place. Moreover, in addition to the widely suggested hot-electron injection mechanism of plasmon, a new photochemical channel has been revealed in the decomposition of DMAB molecules under suitable incident light. This may open up an entire new type of chemical reaction in surface chemistry that we call plasmonic photochemistry. Our theoretical calculations provide consistent interpretations for the experimentally observed pH-,wavelength-,and electrode potential dependence of the SERS spectra of PATP/DMAB adsorbed on silver surfaces. Our findings highlight the important role of theoretical investigations for better understanding of complex processes involved in photochemical reaction of surface adsorbates.

  • 245.
    Duan, Sai
    et al.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry.
    Fang, Ping-Ping
    Fan, Feng-Ru
    Broadwell, Ian
    Yang, Fang-Zu
    Wu, De-Yin
    Ren, Bin
    Amatore, Christian
    Luo, Yi
    KTH, School of Biotechnology (BIO), Theoretical Chemistry.
    Xu, Xin
    Tian, Zhong-Qun
    A density functional theory approach to mushroom-like platinum clusters on palladium-shell over Au core nanoparticles for high electrocatalytic activity2011In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 13, no 12, p. 5441-5449Article in journal (Refereed)
    Abstract [en]

    Recently, it was found that Pt clusters deposited on Pd shell over Au core nanoparticles (Au@Pd@Pt NPs) exhibit unusually high electrocatalytic activity for the electro-oxidation of formic acid (P. P. Fang, S. Duan, et al., Chem. Sci., 2011, 2, 531-539). In an attempt to offer an explanation, we used here carbon monoxide (CO) as probed molecules, and applied density functional theory (DFT) to simulate the surface Raman spectra of CO at this core-shell-cluster NPs with a two monolayer thickness of Pd shell and various Pt cluster coverage. Our DFT results show that the calculated Pt coverage dependent spectra fit the experimental ones well only if the Pt clusters adopt a mushroom-like structure, while currently the island-like structure is the widely accepted model, which follows the Volmer-Weber growth mode. This result infers that there should be a new growth mode, i.e., the mushroom growth mode as proposed in the present work, for Au@Pd@Pt NPs. We suggest that such a mushroom-like structure may offer novel active sites, which accounts for the observed high electrocatalytic activity of Au@Pd@Pt NPs.

  • 246.
    Duan, Sai
    et al.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry.
    Wu, De-Yin
    Xu, Xin
    Luo, Yi
    KTH, School of Biotechnology (BIO), Theoretical Chemistry.
    Tian, Zhong-Qun
    Structures of Water Molecules Adsorbed on a Gold Electrode under Negative Potentials2010In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 114, no 9, p. 4051-4056Article in journal (Refereed)
    Abstract [en]

    Two stable conformations of water hexamer Clusters on gold electrode under negative potentials have been identified by density functional theory calculations. Both form a ring Structure but with different orientations of free CH bonds. Ill one of the Structures, labeled as F-Type, four free OH bonds of the water molecules point toward the gold surface and remain stable over a wide range of the negative potential. The other Structure, labeled as S-Type, starts with five Such free OH bonds pointing toward the gold surface at the low negative potential and ends LIP with six of them at higher negative potential. From the energetic point of view, the S-Type Structure is more stable than the F-Type under the same Potential. By comparing the calculated Raman spectra with the experiment, it is found that S-Type Structures are the most possible surface adsorption state of water molecules at the electrochemical interface under very negative electrode potentials. It is believed that such a novel water Structure Could also exist Oil other negative charged Surfaces.

  • 247.
    Dubeck Schömer, Hanna
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry.
    Medical White Oil in Cosmetic Applications2021Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Moisturizers are the most prescribed products in dermatology, and the most common type of moisturizer delivery systems are lotions and creams. These are emulsions and often contain medical white oil (MWO) due to their protective properties and excellent skin compatibility. The MWO used in cosmetics have traditionally been paraffinic. However, as naphthenic oils often have been proven to create better emulsion stability, this thesis aimed to compare Nynas AB's new MWO, N-MWO, with a paraffinic oil, P-MWO, with similar properties regarding their emulsion stability. The two oils were compared by analyzing their emulsion stability using a rheometer and a Mastersizer 3000 while varying the following factors: type of oil, type of emulsifier, emulsifier concentration, and with and without perfume. The two emulsifying systems used were the commercial product Promulgen D from Lubrizol and the combination of Tween 80 and Span 20. Better emulsion stability and smaller droplet size distribution were obtained when a higher content of Promulgen D was added. However, a higher concentration of Tween 80 and Span 20 did not have the same favorable effect. The results showed that the addition of perfume had no effect, while the type of emulsifier influenced the emulsion stability the most. The samples made from Supela 240 and Tween 80 and Span 20 phase separated. This was more likely due to P-MWOs incompatibility with these emulsifiers as oil type did not influence the emulsion stability when Promulgen D was used as an emulsifier.

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  • 248.
    Dunér, Gunnar
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Thormann, Esben
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Dédinaité, Andra
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Quartz Crystal Microbalance with Dissipation (QCM-D) studies of the viscoelastic response from a continuously growing grafted polyelectrolyte layer2013In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 408, p. 229-234Article in journal (Refereed)
    Abstract [en]

    Poly(acrylic acid) was grown from substrates by photopolymerization, and the grafting process was monitored in situ by Quartz Crystal Microbalance with Dissipation (QCM-D) measurements in a 1:1 v/v mixture of water/ethanol. The polymerization process was monitored into the thick film region, where the change in frequency and dissipation with increasing film mass changes sign as predicted by the Voigt viscoelastic model. Our experimental data are compared with predictions of this model, and satisfactory agreement is found for low overtone numbers. The Voigt model was applied to analyze the measured changes in frequency, Delta f, and dissipation, Delta D, in order to extract information on layer thickness, shear elasticity, mu, and shear viscosity, eta, of the growing film. The increasing rate of changes in Delta f and Delta D observed after about 150 s of polymerization was found to correlate with an increasing growth rate of the film thickness. For longer polymerization times a close to linear increase in thickness with time was observed. The sensitivity, defined as the derivatives of Delta f and Delta D with respect to thickness, depends on overtone number and is different for the frequency and dissipation signals - facts that should be considered when investigating small changes in thick films used in e.g. sensor applications.

  • 249.
    Durif, Olivier
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Piel, Felix
    Department of Chemistry, University of Oslo, Oslo 0315, Norway.
    Wisthaler, Armin
    Department of Chemistry, University of Oslo, Oslo 0315, Norway.
    Nozière, Barbara
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Strong Uptake of Gas-Phase Organic Peroxy Radicals (ROO) by Solid Surfaces Driven by Redox Reactions2024In: JACS Au, E-ISSN 2691-3704, Vol. 4, no 5, p. 1875-1882Article in journal (Refereed)
    Abstract [en]

    Organic peroxy radicals (ROO•) are key oxidants in a wide range of chemical systems such as living organisms, chemical synthesis and polymerization systems, combustion systems, the natural environment, and the Earth’s atmosphere. Although surfaces are ubiquitous in all of these systems, the interactions of organic peroxy radicals with these surfaces have not been studied until today because of a lack of adequate detection techniques. In this work, the uptake and reaction of gas-phase organic peroxy radicals (CH3OO• and i-C3H7OO•) with solid surfaces was studied by monitoring each radical specifically and in real-time with mass spectrometry. Our results show that the uptake of organic peroxy radicals varies widely with the surface material. While their uptake by borosilicate glass and perfluoroalkoxy alkanes (PFA) was negligible, it was substantial with metals and even dominated over the gas-phase reactions with stainless steel and aluminum. The results also indicate that these uptakes are controlled by redox reactions at the surfaces for which the products were analyzed. Our results show that the reactions of organic peroxy radicals with metal surfaces have to be carefully considered in all the experimental investigations of these radicals as they could directly impact the kinetic and mechanistic knowledge derived from such studies.

  • 250. Dvinskikh, S. V.
    et al.
    Furó, Istvan
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry.
    Nuclear magnetic resonance studies of translational diffusion in thermotropic liquid crystals2006In: Russian Chemical Reviews, ISSN 0036-021X, E-ISSN 1468-4837, Vol. 75, no 6, p. 497-506Article in journal (Refereed)
    Abstract [en]

    The experimental NMR techniques for studies of translational diffusion in anisotropic systems and the results of their applications to thermotropic liquid crystals arc reviewed. The main approaches to the theoretical description and computer simulations of diffusion are discussed. The experimental results are compared with computations. The bibliography includes 194 references.

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