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  • 151.
    Cao, Xinrui
    et al.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Ji, Yongfei
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Hu, Wei
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology. Department of Chemical Physics, University of Science and Technology of ChinaHefei, China.
    Duan, Sai
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Luo, Yi
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology. Department of Chemical Physics, University of Science and Technology of ChinaHefei, China .
    Feasible Catalytic Strategy for Writing Conductive Nanoribbons on a Single-Layer Graphene Fluoride2014In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 118, no 39, p. 22643-22648Article in journal (Refereed)
    Abstract [en]

    An accessible method for local reduction of graphene fluoride catalyzed by the Pt-coated nanotip with the assistance of a mixture of hydrogen and ethylene atmosphere is proposed and fully explored theoretically. Detailed mechanisms and roles of hydrogen and ethylene molecules in the cyclic reduction is discussed based on extensive first-principles calculations. It is demonstrated that the proposed cyclic reduction strategy is energetically favorable. This new strategy can be effectively applied in scanning probe lithography to fabricate electronic circuits at the nanoscale on graphene fluoride under mild conditions.

  • 152.
    Cao, Xinrui
    et al.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Ji, Yongfei
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Luo, Yi
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology. University of Science and Technology of China, China.
    Dehydrogenation of Propane to Propylene by a Pd/Cu Single-Atom Catalyst: Insight from First-Principles Calculations2015In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 119, no 2, p. 1016-1023Article in journal (Refereed)
    Abstract [en]

    The catalytic properties of the single-Pd-doped Cu55 nanoparticle toward propane dehydrogenation have been systemically investigated by first-principles calculations, and the possible reaction mechanisms and effects of the single and multiple Pd doping on the catalytic activity have been discussed. Calculations reveal that the low-energy catalytic conversion of propane to propylene by the Pd/Cu single-atom catalyst comprises the initial crucial C–H bond breaking at either the methyl or methylene group, the facile diffusion of detached H atoms on the Cu surface, and the subsequent C–H bond dissociation activation of the adsorbed propyl species. The single-Pd-doped Cu55 nanoparticle shows remarkable activity toward C–H bond activation, and the presence of relatively inactive Cu surface is beneficial for the coupling and desorption of detached H atoms and can reduce side reactions such as deep dehydrogenation and C–C bond breaking. The single-Pd-doped Cu55 cluster bears good balance between the maximum use of the noble metal and the activity, and it may serve as a promising single-atom catalyst toward selective dehydrogenation of propane.

  • 153.
    Carlhamn Rasmussen, Ran
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry.
    Molecular Insights into the Interactions of Monovalent Cations with Highly charged Fatty Acid Monolayers2023Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Vibrational sum frequency spectroscopy has been used to study the interactions of monovalent ions with highly charged fatty acid monolayers. The subphase consisted of selected alkali hydroxide salt solutions of pH 12, primarily focusing on the cesium ion. Molecular information was obtained by targeting the vibrational modes of the carboxylic acid headgroups, alkyl chains, and water molecules in the immediate surface and diffuse double layers. The surface charge was estimated by monitoring the stretching modes of the hydrated carboxylate and protonated carboxylic acid. The surface potential was estimated from the signal response of the water molecules in the diffuse double layer. The behaviour of the surface charge and surface potential agrees well with Gouy-Chapman theory for large areas per molecule, but deviates significantly upon monolayer compression. At small areas per molecule or high surface charge density, the results better align with a size-modified version of the Poisson-Boltzmann theory. The results obtained with a cesium hydroxide subphase were compared to equivalent experiments with sodium and lithium, which puts the cesium ion into context with the other alkali ions in terms ion specific effects. The results collected here provide insight into how effective ion size can be used in modelling and predicting ion specific effects with the carboxylic acid moiety in a Langmuir monolayer.

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  • 154.
    Carlqvist, Peter
    et al.
    KTH, Superseded Departments (pre-2005), Chemistry.
    Ostmark, H.
    Brinck, Tore
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry.
    The stability of arylpentazoles2004In: Journal of Physical Chemistry A, ISSN 1089-5639, E-ISSN 1520-5215, Vol. 108, no 36, p. 7463-7467Article in journal (Refereed)
    Abstract [en]

    The stability of phenylpentazole along with para-substituted and ortho,para-substituted arylpentazoles have been studied using high-level density functional theory (DFT). The decomposition of arylpentazoles to N-2 and the corresponding azide is a first-order reaction, where the breaking of the N1-N2 bond is concomitant with cleavage of the N3-N4 bond. Calculations confirm that the stability of arylpentazoles increases with electron-donating groups and decreases with electron-withdrawing groups, in the para position, as found in experiments. The stabilizing effect of the electron-donating groups is shown to be due to a resonance interaction with the electron-withdrawing pentazole ring. Addition of solvation effects, using the polarizable continuum model to simulate the polar solvent methanol, increases the stability of arylpentazoles. This is due to a more polar ground state than transition state. The calculated free energies of activation for the arylpentazoles agree well with experimental results. From the calculations, the electron-withdrawing effect of the pentazole group is found to be similar to that of cyanide (-CN). Some new arylpentazoles with hydroxyl groups in the ortho position are proposed. These are predicted to be more stable than all previously synthesized neutral arylpentazoles.

  • 155.
    Carlsson, Celice
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry.
    Fégeant, Benjamin
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry.
    Svensson, Emelie
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry.
    Wiklund, Love
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry.
    Jonsson, Mats
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    On the Selectivity of Radical Scavengers Used To Probe Hydroxyl Radical Formation in Heterogeneous Systems2022In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 126, no 30, p. 12435-12440Article in journal (Refereed)
    Abstract [en]

    Tris and methanol have been used quite extensively as probes for surface-bound hydroxyl radicals in heterogeneous systems, such as TiO2 photocatalysis and catalytic decomposition of H2O2. Recent studies have indicated that the selectivity for surface-bound hydroxyl radicals is questionable and that the yield of the stable detectable product, formaldehyde, may be different for different reactive species. In this work, we have explored the selectivity as well as the formaldehyde yield of these two probes by experimentally studying formaldehyde formation in homogeneous (gamma radiolysis) and heterogeneous (TiO2 photocatalysis) systems, where hydroxyl radicals and Br-2.- can be formed. The latter is formed in the reaction between hydroxyl radicals and Br- at relatively high concentrations of Br-. The experiments clearly show that the formaldehyde yield is reduced by 85% when comparing hydroxyl radicals and Br2 & BULL;- in a homogeneous methanol system and increased by 50% when making the same comparison for the homogeneous Tris system. The increased yield is attributed to a change in the reaction mechanism as Br2 & BULL;- is mainly expected to produce a nitrogen-centered radical cation, while the hydroxyl radical mainly produces carbon-centered radicals. The radical cation appears to produce formaldehyde with a higher yield. In the photocatalysis system, the trends are similar but even more emphasized. The rationale for this is discussed, as well as the suitability of methanol and Tris as probes for surface-bound hydroxyl radicals in heterogeneous systems.

  • 156.
    Carlsson, Celice
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering.
    Wiklund, Love
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering.
    Svensson, Emilie
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering.
    Fégeant, Benjamin
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering.
    Photocatalytic Degradation of Organic Substances in Salt Water2021Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The purpose of this research was to investigate the kinetics and mechanisms of the photocatalytic degradation of organic substances in the presence of anions (bromide and chloride), using titanium dioxide as a photocatalyst. Tris(hydroxymethyl)aminomethane (Tris) and methanol were the organic substances used as probes. Photocatalytic degradation of the probes produces formaldehyde through reaction with hydroxyl radicals at the surface of the photocatalyst. The product was quantified using a modified Hantzsch reaction and UV-Vis spectroscopy at the fixed wavelength 368 nm. It was found that having bromide present in the reaction mixture resulted in an increase in the rate of formation of formaldehyde from Tris, while it resulted in a decrease from methanol. Bromide on the surface of the photocatalyst reacts with the hydroxyl radicals to form reactive halogen species (RHS). This study proposes that the RHS Br2•- oxidises the probe into a cation radical, which initialises the probe degradation and the subsequent formation of formaldehyde. Conversion from hydroxyl radicals to RHS leads to a greater selectivity in formaldehyde production. Increased selectivity of attack towards electron-rich centres can explain the observed results with the different probes in this study. A linear combination expression of the total production of formaldehyde was developed, through which the X-factor, a ratio of the production of formaldehyde by RHS relative to the production of formaldehyde by hydroxyl radicals, was calculated. However, no realistic values were obtained when calculating the X-factor for different anion concentrations, thus indicating that factors other than competition kinetics affect the degradation. No conclusions could be drawn regarding the effect of chloride on the formation of formaldehyde from Tris and methanol, as the results were ambiguous.

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  • 157. Carravetta, V.
    et al.
    Ågren, Hans
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Symmetry Breaking and Hole Localization in Multiple Core Electron Ionization2013In: Journal of Physical Chemistry A, ISSN 1089-5639, E-ISSN 1520-5215, Vol. 117, no 31, p. 6798-6802Article in journal (Refereed)
    Abstract [en]

    Motivated by recent opportunitites to study hollow molecules with multiple core holes offered by X-ray free electron lasers, we revisit the core-hole localization and symmetry breaking problem, now studying ionization of more than one core electron. It is shown, using a N-2 molecule with one, two, three, and four core holes, for example, that in a multiconfigurational determination of the core ionization potentials employing a molecular point group with broken inversion symmetry, one particular configuration is sufficient to account for the symmetry breaking relaxation energy in an independent particle approximation in the case of one or three holes, whereas the choice of point group symmetry is unessential for two and four holes. The relaxation energy follows a quadratic dependence on the number of holes in both representations.

  • 158. Casalongue, Hernan G. Sanchez
    et al.
    Benck, Jesse D.
    Tsai, Charlie
    Karlsson, Rasmus K. B.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Kaya, Sarp
    Ng, May Ling
    Pettersson, Lars G. M.
    Abild-Pedersen, Frank
    Norskov, J. K.
    Ogasawara, Hirohito
    Jaramillo, Thomas F.
    Nilsson, Anders
    Operando Characterization of an Amorphous Molybdenum Sulfide Nanoparticle Catalyst during the Hydrogen Evolution Reaction2014In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 118, no 50, p. 29252-29259Article in journal (Refereed)
    Abstract [en]

    Molybdenum sulfide structures, particularly amorphous MoS3 nanoparticles, are promising materials in the search for cost-effective and scalable water-splitting catalysts. Ex situ observations show that the nanoparticles exhibit a composition change from MoS3 to defective MoS2 when subjected to hydrogen evolution reaction (HER) conditions, raising questions regarding the active surface sites taking part in the reaction. We tracked the in situ transformation of amorphous MoS3 nanoparticles under HER conditions through ambient pressure X-ray photoelectron spectroscopy and performed density functional theory studies of model MoSx systems. We demonstrate that, under operating conditions, surface sites are converted from MoS3 to MoS2 in a gradual manner and that the electrolytic current densities are proportional to the extent of the transformation. We also posit that it is the MoS2 edge-like sites that are active during HER, with the high activity of the catalyst being attributed to the increase in surface MoS2 edge-like sites after the reduction of MoS3 sites.

  • 159.
    Cassir, M.
    et al.
    PSL Res Univ, Chim Paristech, CNRS, Inst Rech Chim Paris, 11 Rue Pierre & Marie Curie, F-75231 Paris 05, France..
    Lagergren, Carina
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Applied Electrochemistry.
    Guest editorial-IWMC20192021In: International journal of hydrogen energy, ISSN 0360-3199, E-ISSN 1879-3487, Vol. 46, no 28, p. 14897-14897Article in journal (Other academic)
  • 160.
    Celania, Chris
    et al.
    Department of Materials and Environmental Chemistry, Stockholm University, Svante Arrhenius väg 16 C, 10691 Stockholm, Sweden.
    Smetana, Volodymyr
    Department of Materials and Environmental Chemistry, Stockholm University, Svante Arrhenius väg 16 C, 10691 Stockholm, Sweden; intelligent Advanced Materials, Department of Biological and Chemical Engineering and iNANO, Aarhus University, 8000 Aarhus C, Denmark.
    Meyer, Gerd
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry. Department of Chemistry, Universität zu Köln, Greinstraße 6, 50939 Köln, Germany.
    Mudring, Anja Verena
    Department of Materials and Environmental Chemistry, Stockholm University, Svante Arrhenius väg 16 C, 10691 Stockholm, Sweden; intelligent Advanced Materials, Department of Biological and Chemical Engineering and iNANO, Aarhus University, 8000 Aarhus C, Denmark.
    The Prolific Ternary System Pt/Sn/Nd: Insertion of Pt into the Structures of Sn/Nd Intermetallics Yields Structural Complexity and Wealth2023In: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 62, no 24, p. 9369-9378Article in journal (Refereed)
    Abstract [en]

    The understanding of structure and bonding in intermetallic phases still lags behind that of molecular compounds. For that reason, exploring intermetallic phases and identifying structural patterns and relationships are particularly important for closing this knowledge gap. In particular, here we report on the addition of increasing amounts of platinum to ∼2:1 mixtures of tin and neodymium, which yields eight ternary Pt/Sn/Nd compounds, four of which have not been reported before. Interestingly, except for PtSnNd (1), all observed ternary phases of the system can be derived from the binary compounds Sn2Nd and Sn5Nd2 by adding Pt to the composition(s), as they lie on or close to two lines: Sn2Nd-Pt (Pt0.21(1)Sn2Nd (2), PtSn2Nd (3), Pt1.33Sn2Nd (4), Pt2-xSn2+xNd (x = 0.27(3), 5), and Pt3Sn2Nd (6)) or Sn5Nd2-Pt (Pt1.5Sn5-xNd2 (x = 0.16(2), 7) and Pt3Sn5Nd2-x (x = 0.161(8), 8)). While the introduction of increasing amounts of Pt to the binaries Sn2Nd and Sn5Nd2 leads to stepwise changes in the coordination environment of Nd, Pt preserves its coordination over the entire system in the form of interpenetrating bipyramidal {PtSn5Nd5} clusters.

  • 161.
    Cerrato, C. P.
    et al.
    Department of Microbiology, Tumor and Cancer Biology, Karolinska Institutet, Stockholm, Sweden.
    Kivijärvi, Tove
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Langel, Ü.
    Department of Biochemistry and Biophysics, the Arrhenius Laboratories for Natural Sciences, Stockholm University, Stockholm, Sweden Laboratory of Molecular Biotechnology, Institute of Technology, University of Tartu, Tartu, Estonia.
    Mitochondrial Targeting Probes, Drug Conjugates, and Gene Therapeutics2022In: Cell Penetrating Peptides, Springer Nature , 2022, p. 429-446Chapter in book (Refereed)
    Abstract [en]

    Mitochondria represent an important drug target for many phatology, including neurodegeneration, metabolic disease, heart failure, ischemia-reperfusion injury, and cancer. Mitochondrial dysfunctions are caused by mutation in mitochondrial DNA or in nuclear genes encoding mitochondrial proteins. Cell-penetrating peptides (CPPs) have been employed to overcome biological barriers, target this organelle, and therapeuticaly restore mitochondrial functions. Here, we describe recent methods used to deliver oligonucleotides targeting mitochondrial protein by using mitochondrial penetrating peptides. In particular, we highlight recent advances of formulated peptides/oligonucleotides nanocomplexes as a proof-of-principle for pharmaceutical form of peptide-based therapeutics.

  • 162.
    Cha, Gihoon
    et al.
    Univ Erlangen Nurnberg, Inst Surface Sci & Corros WW4 LKO, Dept Mat Sci, Martensstr 7, D-91058 Erlangen, Germany..
    Hwang, Imgon
    Univ Erlangen Nurnberg, Inst Surface Sci & Corros WW4 LKO, Dept Mat Sci, Martensstr 7, D-91058 Erlangen, Germany..
    Hejazi, Seyedsina
    Univ Erlangen Nurnberg, Inst Surface Sci & Corros WW4 LKO, Dept Mat Sci, Martensstr 7, D-91058 Erlangen, Germany.;Univ Siegen, Chem & Struct Novel Mat, Paul Bonatz Str 9-11, D-57076 Siegen, Germany..
    Dobrota, Ana S.
    Univ Belgrade, Fac Phys Chem, Studentski Trg 12-16, Belgrade 11000, Serbia..
    Pašti, Igor A.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Structures. Univ Belgrade, Fac Phys Chem, Studentski Trg 12-16, Belgrade 11000, Serbia..
    Osuagwu, Benedict
    Univ Erlangen Nurnberg, Inst Surface Sci & Corros WW4 LKO, Dept Mat Sci, Martensstr 7, D-91058 Erlangen, Germany..
    Kim, Hyesung
    Univ Erlangen Nurnberg, Inst Surface Sci & Corros WW4 LKO, Dept Mat Sci, Martensstr 7, D-91058 Erlangen, Germany..
    Will, Johannes
    Univ Erlangen Nurnberg, Inst Micro & Nanostruct Res & Ctr Nanoanal & Elec, IZNF, Cauerstr 3, D-91058 Erlangen, Germany..
    Yokosawa, Tadahiro
    Univ Erlangen Nurnberg, Inst Micro & Nanostruct Res & Ctr Nanoanal & Elec, IZNF, Cauerstr 3, D-91058 Erlangen, Germany..
    Badura, Zdenek
    Reg Ctr Adv Technol & Mat, Slechtitelu 27, Olomouc 78371, Czech Republic..
    Kment, Stepan
    Reg Ctr Adv Technol & Mat, Slechtitelu 27, Olomouc 78371, Czech Republic..
    Mohajernia, Shiva
    Univ Erlangen Nurnberg, Inst Surface Sci & Corros WW4 LKO, Dept Mat Sci, Martensstr 7, D-91058 Erlangen, Germany.;Univ Siegen, Chem & Struct Novel Mat, Paul Bonatz Str 9-11, D-57076 Siegen, Germany..
    Mazare, Anca
    Univ Erlangen Nurnberg, Inst Surface Sci & Corros WW4 LKO, Dept Mat Sci, Martensstr 7, D-91058 Erlangen, Germany..
    Skorodumova, Natalia V.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering. Uppsala Univ, Dept Phys & Astron, Box 516, S-75120 Uppsala, Sweden..
    Spiecker, Erdmann
    Univ Erlangen Nurnberg, Inst Micro & Nanostruct Res & Ctr Nanoanal & Elec, IZNF, Cauerstr 3, D-91058 Erlangen, Germany..
    Schmuki, Patrik
    Univ Erlangen Nurnberg, Inst Surface Sci & Corros WW4 LKO, Dept Mat Sci, Martensstr 7, D-91058 Erlangen, Germany.;Reg Ctr Adv Technol & Mat, Slechtitelu 27, Olomouc 78371, Czech Republic.;King Abdulaziz Univ, Fac Sci, Dept Chem, POB 80203, Jeddah 21569, Saudi Arabia..
    As a single atom Pd outperforms Pt as the most active co-catalyst for photocatalytic H-2 evolution2021In: ISCIENCE, ISSN 2589-0042, Vol. 24, no 8, article id 102938Article in journal (Refereed)
    Abstract [en]

    Here, we evaluate three different noble metal co-catalysts (Pd, Pt, and Au) that are present as single atoms (SAs) on the classic benchmark photocatalyst, TiO2. To trap the single atoms on the surface, we introduced controlled surface vacancies (Ti3+-Ov) on anatase TiO2 nanosheets by a thermal reduction treatment. After anchoring identical loadings of single atoms of Pd, Pt, and Au, we measure the photocatalytic H-2 generation rate and compare it to the classic nanoparticle co-catalysts on the nanosheets. While nanoparticles yield the well-established the hydrogen evolution reaction activity sequence (Pt > Pd > Au), for the single atom form, Pd radically outperforms Pt and Au. Based on density functional theory (DFT), we ascribe this unusual photocatalytic co-catalyst sequence to the nature of the charge localization on the noble metal SAs embedded in the TiO2 surface.

  • 163.
    Chakraborty, Pratip
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Theoretical Chemistry and Biology.
    Couto, Rafael Carvalho
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Theoretical Chemistry and Biology.
    Holmgaard List, Nanna
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Theoretical Chemistry and Biology.
    Deciphering Methylation Effects on S2(ππ*) Internal Conversion in the Simplest Linear α,β-Unsaturated Carbonyl2023In: Journal of Physical Chemistry A, ISSN 1089-5639, E-ISSN 1520-5215, Vol. 127, no 25, p. 5360-5373Article in journal (Refereed)
    Abstract [en]

    Chemical substituents can influence photodynamics by altering the location of critical points and the topography of the potential energy surfaces (electronic effect) and by selectively modifying the inertia of specific nuclear modes (inertial effects). Using nonadiabatic dynamics simulations, we investigate the impact of methylation on S2(ππ*) internal conversion in acrolein, the simplest linear α,β-unsaturated carbonyl. Consistent with time constants reported in a previous time-resolved photoelectron spectroscopy study, S2 → S1 deactivation occurs on an ultrafast time scale (∼50 fs). However, our simulations do not corroborate the sequential decay model used to fit the experiment. Instead, upon reaching the S1 state, the wavepacket bifurcates: a portion undergoes ballistic S1 → S0 deactivation (∼90 fs) mediated by fast bond-length alternation motion, while the remaining decays on the picosecond time scale. Our analysis reveals that methyl substitution, generally assumed to mainly exert inertial influence, is also manifested in important electronic effects due to its weak electron-donating ability. While methylation at the β C atom gives rise to effects principally of an inertial nature, such as retarding the twisting motion of the terminal −CHCH3 group and increasing its coupling with pyramidalization, methylation at the α or carbonyl C atom modifies the potential energy surfaces in a way that also contributes to altering the late S1-decay behavior. Specifically, our results suggest that the observed slowing of the picosecond component upon α-methylation is a consequence of a tighter surface and reduced amplitude along the central pyramidalization, effectively restricting the access to the S1/S0-intersection seam. Our work offers new insight into the S2(ππ*) internal conversion mechanisms in acrolein and its methylated derivatives and highlights site-selective methylation as a tuning knob to manipulate photochemical reactions.

  • 164.
    Chatre, Clément
    et al.
    Université de Lyon, Université Claude Bernard Lyon 1, CNRS, IRCELYON UMR 5256, 69626 Villeurbanne, France.
    Ehret, Eric
    Université de Lyon, Université Claude Bernard Lyon 1, CNRS, IRCELYON UMR 5256, 69626 Villeurbanne, France.
    Ondarçuhu, Thierry
    Université de Toulouse, CNRS, IMFT INPT-UPS, 31400 Toulouse, France.
    Steyer, Philippe
    Univ. Lyon, INSA de Lyon, Université Claude Bernard Lyon 1, CNRS, MATEIS, UMR 5510, 69621 Villeurbanne, France.
    Masenelli-Varlot, Karine
    Univ. Lyon, INSA de Lyon, Université Claude Bernard Lyon 1, CNRS, MATEIS, UMR 5510, 69621 Villeurbanne, France.
    Cadete Santos Aires, Francisco José
    Université de Lyon, Université Claude Bernard Lyon 1, CNRS, IRCELYON UMR 5256, 69626 Villeurbanne, France;National Research Tomsk State University, LCR, 634050 Tomsk, Russia.
    Nozière, Barbara
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Influence of Surface-Active Substances and Substrates on the Wettability of Individual Aerosol Particles during Condensation by Environmental Scanning Electron Microscopy2023In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 39, no 8, p. 2957-2965Article in journal (Refereed)
    Abstract [en]

    The formation of liquid cloud droplets from aerosol particles in the Earth atmosphere is still under debate particularly because of the difficulties to quantify the importance of bulk and surface effects in these processes. Recently, single-particle techniques have been developed to access experimental key parameters at the scale of individual particles. Environmental scanning electron microscopy (ESEM) has the advantage to provide in situ monitoring of the water uptake of individual microscopic particles deposited on solid substrates. In this work, ESEM was used to compare droplet growth on pure ammonium sulfate (NH4)2SO4 and mixed sodium dodecyl sulfate/ammonium sulfate (SDS/(NH4)2SO4) particles and to explore the role of experimental parameters, such as the hydrophobic–hydrophilic character of the substrate, on this growth. With hydrophilic substrates, the growth on pure salt particles was strongly anisotropic, but this anisotropy was suppressed by the presence of SDS. With hydrophobic substrates, it is the wetting behavior of the liquid droplet that is impacted by the presence of SDS. The wetting behavior of the pure (NH4)2SO4 solution on a hydrophobic surface shows a step-by-step mechanism that can be attributed to successive pinning–depinning phenomena at the triple-phase line frontier. Unlike the pure (NH4)2SO4 solution, the mixed SDS/(NH4)2SO4 solution did not show such a mechanism. Therefore, the hydrophobic–hydrophilic character of the substrate plays an important role in the stability and dynamics of the liquid droplets’ nucleation by water vapor condensation. In particular, hydrophilic substrates are not suited for the investigation of the hygroscopic properties (deliquescence relative humidity (DRH) and hygroscopic growth factor (GF)) of particles. Using hydrophobic substrates, data show that the DRH of (NH4)2SO4 particles is measured within 3% accuracy on the RH and their GF could indicate a size-dependent effect in the micrometer range. The presence of SDS does not seem to modify the DRH and GF of (NH4)2SO4 particles. This study shows that the water uptake on deposited particles is a complex process but, once carefully taken into account, ESEM is a suitable technique to study them.

  • 165.
    Chattopadhyaya, Mausumi
    et al.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Murugan, N. Arul
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Rinkevicius, Zilvinas
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology. KTH, Centres, SeRC - Swedish e-Science Research Centre.
    Origin of the Absorption Band of Bromophenol Blue in Acidic and Basic pH: Insight from a Combined Molecular Dynamics and TD-DFT/MM Study2016In: Journal of Physical Chemistry A, ISSN 1089-5639, E-ISSN 1520-5215, Vol. 120, no 36, p. 7175-7182Article in journal (Refereed)
    Abstract [en]

    We study the linear and nonlinear optical properties of a well-known acid base indicator, bromophenol blue (BPB), in aqueous solution by employing static and integrated approaches. In the static approach, optical properties have been calculated using time-dependent density functional theory (TD-DFT) on the fully relaxed geometries of the neutral and different unprotonated forms of BPB. Moreover, both closed and open forms of BPB were considered. In the integrated approach, the optical properties have been computed over many snapshots extracted from molecular dynamics simulation using a hybrid time-dependent density functional theory/molecular mechanics approach. The static approach suggests closed neutral double right arrow anionic interconversion as the dominant mechanism for the red shift in the absorption spectra of BPB due to a change from acidic to basic pH. It is found by employing an integrated approach that the two interconversions, namely open neutral double right arrow anionic and open neutral double right arrow dianionic, can contribute to the pH- dependent shift in the absorption spectra of BPB. Even though both static and integrated approaches reproduce the pH-dependent red shift in the absorption spectra of BPB, the latter one is suitable to determine both the spectra and spectral broadening. Finally, the computed static first hyperpolarizability for various protonated and deprotonated forms of BPB reveals that this molecule can be used as a nonlinear optical probe for pH sensing in addition to its highly exploited use as an optical probe.

  • 166. Chattopadhyaya, Mausumi
    et al.
    Natarajan Arul, Murgan
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Alam, Md. Mehboob
    Chakrabarti, Swapan
    Spatial spin-charge separation in neutral endohedral metallofullerene: A combined restricted open-shell MP2 and Car-Parrinello molecular dynamics study2013In: Chemical Physics Letters, ISSN 0009-2614, E-ISSN 1873-4448, Vol. 557, p. 71-75Article in journal (Refereed)
    Abstract [en]

    We present the first theoretical evidence of the unusual separation of spin and charge degrees of freedom of electron in a neutral endohedral metallofullerene, Sc@C-50. To demystify its origin, we have performed computation at the level of ROMP2 in combination with Car-Parrinello molecular dynamics at 300 K on a series of Sc@C-n. Our inspection reveals that a sharp fall of electron correlation in Sc@C-50 makes the system so sensitive that, to avoid additional Pauli repulsion, Sc leaves the charge component of the solitary 3d electron to C-50 keeping the spin density over its own.

  • 167.
    Chaudhary, Himanshu
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Ferreira Fernandes, Ricardo M.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry. Centro de Investigação em Química, Department of Chemistry and Biochemistry, Faculty of Science, University of Porto, Rua do Campo Alegre, s/n, Porto, P-4169-007, Portugal.
    Gowda, Vasantha
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Claessens, Mirelle M. A. E.
    Furo, Istvan
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Lendel, Christofer
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Intrinsically disordered protein as carbon nanotube dispersant: How dynamic interactions lead to excellent colloidal stability2019In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 556, p. 172-179Article in journal (Refereed)
    Abstract [en]

    The rich pool of protein conformations combined with the dimensions and properties of carbon nanotubes create new possibilities in functional materials and nanomedicine. Here, the intrinsically disordered protein α-synuclein is explored as a dispersant of single-walled carbon nanotubes (SWNTs) in water. We use a range of spectroscopic methods to quantify the amount of dispersed SWNT and to elucidate the binding mode of α-synuclein to SWNT. The dispersion ability of α-synuclein is good even with mild sonication and the obtained dispersion is very stable over time. The whole polypeptide chain is involved in the interaction accompanied by a fraction of the chain changing into a helical structure upon binding. Similar to other dispersants, we observe that only a small fraction (15–20%) of α-synuclein is adsorbed on the SWNT surface with an average residence time below 10 ms

  • 168.
    Chen, Dihao
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Surface and Corrosion Science. Univ Sci & Technol Beijing, Inst Adv Mat & Technol, Beijing Adv Innovat Ctr Mat Genome Engn, Key Lab Corros & Protect MOE, Beijing 100083, Peoples R China..
    Dong, Chaofang
    Univ Sci & Technol Beijing, Inst Adv Mat & Technol, Beijing Adv Innovat Ctr Mat Genome Engn, Key Lab Corros & Protect MOE, Beijing 100083, Peoples R China..
    Pan, Jinshan
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Surface and Corrosion Science.
    Engelhardt, George R.
    OLI Syst Inc, 2 Gatehall Dr, Parsippany, NJ 07054 USA..
    Macdonald, Digby D.
    Univ Calif Berkeley, Dept Nucl Engn & Mat Sci & Engn, Berkeley, CA 94720 USA..
    Development of the General Methodology for Determining the Point of Zero Charge of Oxide Films by Contact Angle Titration2023In: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 170, no 8, article id 081504Article in journal (Refereed)
    Abstract [en]

    The point of zero charge (pH(pzc)) is one of the most important properties in determining the nature of the surface charge on oxide films in contact with aqueous solutions. Contact angle titration is a simple, rapid and direct surface titration approach to determine the pH(pzc) of oxide films, compared with mass titration, potentiometric titration and batch equilibration method. Although contact angle titration has been an effective method to estimate the pH(pzc) in the past, there are some limitations in previous methodologies for the correlation between the contact angle and the surface charge density, due to the consideration of only the negative charged OH- at surface or the absence of a vital part of solution potential for the electrochemical potential of H+ in electrolyte. Based on the work of many previous contributors, two general thermodynamic methods for determining the pHpzc of oxide films by contact angle titration are developed here. The methods provide precise, fundamental understandings of the variation of the contact angle with surface charge density, which is of great significance for interfacial science.

  • 169. Chen, P.
    et al.
    Nishiyama, Y.
    Wohlert, Jakob
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Biocomposites.
    Quantifying the influence of dispersion interactions on the elastic properties of crystalline cellulose2021In: Cellulose, ISSN 0969-0239, E-ISSN 1572-882X, Vol. 28, no 17, p. 10777-10786Article in journal (Refereed)
    Abstract [en]

    Dispersion and electrostatic interactions both contribute significantly to the tight assembly of macromolecular chains within crystalline polysaccharides. Using dispersion-corrected density functional theory (DFT) calculation, we estimated the elastic tensor of the four crystalline cellulose allomorphs whose crystal structures that are hitherto available, namely, cellulose Iα, Iβ, II, IIII. Comparison between calculations with and without dispersion correction allows quantification of the exact contribution of dispersion to stiffness at molecular level.

  • 170.
    Chen, Pan
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Nishiyama, Yoshiharu
    Wohlert, Jakob
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Lu, Ang
    Mazeau, Karim
    Ismail, Ahmed E.
    Translational Entropy and Dispersion Energy Jointly Drive the Adsorption of Urea to Cellulose2017In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 121, no 10, p. 2244-2251Article in journal (Refereed)
    Abstract [en]

    The adsorption of urea on cellulose at room temperature has been studied using adsorption isotherm experiments and molecular dynamics (MD) simulations. The immersion of cotton cellulose into bulk urea solutions with concentrations between 0.01 and 0.30 g/mL led to a decrease in urea concentration in all solutions, allowing the adsorption of urea on the cellulose surface to be measured quantitatively. MD simulations suggest that urea molecules form sorption layers on both hydrophobic and hydrophilic surfaces. Although electrostatic interactions accounted for the majority of the calculated interaction energy between urea and cellulose, dispersion interactions were revealed to be the key driving force for the accumulation of urea around cellulose. The preferred orientation of urea and water molecules in the first solvation shell varied depending on the nature of the cellulose surface, but urea molecules were systematically oriented parallel to the hydrophobic plane of cellulose. The translational entropies of urea and water molecules, calculated from the velocity spectrum of the trajectory, are lower near the cellulose surface than in bulk. As urea molecules adsorb on cellulose and expel surface water into the bulk, the increase in the translational entropy of the water compensated for the decrease in the entropy of urea, resulting in a total entropy gain of the solvent system. Therefore, the cellulose urea dispersion energy and the translational entropy gain of water are the main factors that drive the adsorption of urea on cellulose.

  • 171.
    Chen, Pan
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center. South China Univ Technol, State Key Lab Pulp & Paper Engn, Guangzhou 510640, Guangdong, Peoples R China.
    Ogawa, Yu
    Univ Grenoble Alpes, CNRS, CERMAV, BP53, F-38000 Grenoble 9, France..
    Nishiyama, Yoshiharu
    Univ Grenoble Alpes, CNRS, CERMAV, BP53, F-38000 Grenoble 9, France..
    Ismail, Ahmed E.
    West Virginia Univ, Dept Chem & Biomed Engn, Morgantown, WV 26505 USA..
    Mazeau, Karim
    Univ Grenoble Alpes, CNRS, CERMAV, BP53, F-38000 Grenoble 9, France..
    I alpha to I beta mechano-conversion and amorphization in native cellulose simulated by crystal bending2018In: Cellulose, ISSN 0969-0239, E-ISSN 1572-882X, Vol. 25, no 8, p. 4345-4355Article in journal (Refereed)
    Abstract [en]

    The bending of rod-like native cellulose crystals with degree of polymerization 40 and 160 using molecular dynamics simulations resulted in a deformation-induced local amorphization at the kinking point and allomorphic interconversion between cellulose I alpha and I beta in the unbent segments. The transformation mechanism involves a longitudinal chain slippage of the hydrogen-bonded sheets by the length of one anhydroglucose residue ( 0.5 nm), which alters the chain stacking from the monotonic (I alpha) form to the alternating I beta one or vice versa. This mechanical deformation converts the I alpha form progressively to the I beta form, as has been experimentally observed for ultrasonication of microfibrils. I beta is also able to partially convert to I alpha-like organization but this conversion is only transitory. The qualitative agreement between the behavior of ultrasonicated microfibrils and in silico observed I alpha -> I beta conversion suggests that shear deformation and chain slippage under bending deformation is a general process when cellulose fibrils experience lateral mechanical stress.

  • 172.
    Chen, Pan
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Fibre Technology. Beijing Inst Technol, Sch Mat Sci & Engn, Beijing Engn Res Ctr Cellulose & Derivat, Beijing 100081, Peoples R China..
    Wohlert, Jakob
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Biocomposites.
    Berglund, Lars
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Furo, Istvan
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center.
    Water as an Intrinsic Structural Element in Cellulose Fibril Aggregates2022In: Journal of Physical Chemistry Letters, ISSN 1948-7185, E-ISSN 1948-7185, Vol. 13, no 24, p. 5424-5430Article in journal (Refereed)
    Abstract [en]

    While strong water association with cellulose in plant cell walls and man-made materials is well-established, its molecular scale aspects are not fully understood. The thermodynamic consequences of having water molecules located at the microfibril-microfibril interfaces in cellulose fibril aggregates are therefore analyzed by molecular dynamics simulations. We find that a thin layer of water molecules at those interfaces can be in a state of thermal equilibrium with water surrounding the fibril aggregates because such an arrangement lowers the free energy of the total system. The main reason is enthalpic: water at the microfibril- microfibril interfaces enables the cellulose surface hydroxyls to experience a more favorable electrostatic environment. This enthalpic gain overcomes the entropic penalty from strong immobilization of water molecules. Hence, those particular water molecules stabilize the cellulose fibril aggregates, akin to the role of water in some proteins. Structural and functional hypotheses related to this finding are presented.

  • 173.
    Chen, Song
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Resource recovery.
    Wang, Shihuai
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Li, Hu
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Tillämpad materialvetenskap..
    Forsberg, Kerstin
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Resource recovery.
    Eu3+ doped monetite and its use as fluorescent agent for dental restorations2018In: Ceramics International, ISSN 0272-8842, E-ISSN 1873-3956, Vol. 44, no 9, p. 10510-10516Article in journal (Refereed)
    Abstract [en]

    It is essential but challenging to distinguish the dental restorations from the surrounding teeth when removing filling materials from cavity. In this study, Eu3+ doped monetite was proposed as a fluorescent agent for dental restorations to meet this challenge. Eu3+ doped monetite with enhanced fluorescent property was obtained via a precipitation method. The presence of Eu3+ could prevent the phase transformation of brushite to monetite. However, all the brushite particles transformed to monetite at 300 °C and to tricalcium phosphate at 800 °C. The emission intensity increased with the addition of Eu3+ and reached the maximum when 12 mol% Eu3+ was added into the aqueous solution. With either 254 nm or 393 nm excitation, Eu3+ doped monetite showed the strongest fluorescence emission peaking at 616 nm and other two moderate bands peaking at 699 nm and 593 nm. The excitation spectra at the emission wavelength of 616 nm showed strong absorption peaks at 254 nm and 393 nm. We further investigate the fluorescence properties of Eu3+ doped monetite in one type of dental restorations. Glass ionomer cement with Eu3+ doped monetite exhibited clear fluoresce with origin color under UV irradiation at 254 nm, showing that Eu3+doped monetite is a promising fluorescent agent for dental restorations.

  • 174. Chen, W.
    et al.
    Guo, R.
    Tang, H.
    Wienhold, K. S.
    Li, N.
    Jiang, Z.
    Tang, J.
    Jiang, X.
    Kreuzer, L. P.
    Liu, H.
    Schwartzkopf, M.
    Sun, X. W.
    Roth, Stephan V.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Biocomposites. Deutsches Elektronen-Synchrotron DESY, Notkestraße 85, 22607 Hamburg, Germany.
    Wang, K.
    Xu, B.
    Müller-Buschbaum, P.
    Operando structure degradation study of PbS quantum dot solar cells2021In: Energy & Environmental Science, ISSN 1754-5692, E-ISSN 1754-5706, Vol. 14, no 6, p. 3420-3429Article in journal (Refereed)
    Abstract [en]

    PbS quantum dot (QD) solar cells demonstrate great potential in solar energy conversion with a broad and flexible spectral response. Even though long-term storage stabilities of QD solar cells were reported in literature, the operation stability from a more practical aspect, to date, has been not yet investigated. Herein, we observe the structure degradation process of a PbS QD-ink based solar cell during the device operation. Simultaneously to probing the solar cell parameters, the overall structure evolutions of the QDs in both, active layer and hole transport layer of the solar cell are studied with grazing-incidence small- and wide-angle X-ray scattering (GISAXS/GIWAXS). We find a spontaneous decrease of the QD inter-dot distance with an increase in the spatial disorder in the active layer (PbX2-PbS QDs, X = I, and Br) during the operation induced degradation. Consequently, the structure disorder-induced broadening of the energy state distribution is responsible for the decrease in open-circuit voltageVocleading to the device degradation. These findings elucidate the origin of light-soaking as well as the structure degradation of QD ink-based solar cells and indicate that the stability of the device can be realized by the positional stabilization of the QDs in the QD solid.

  • 175.
    Chen, Xiaoyu
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Theoretical Chemistry and Biology.
    Ahlquist, Mårten S. G.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Theoretical Chemistry and Biology.
    Deconstructing the Enhancing Effect on CO2 Activation in the Electric Double Layer with EVB Dynamic Reaction Modeling2020In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 124, no 41, p. 22479-22487Article in journal (Refereed)
    Abstract [en]

    The reactivities of the same molecular electrocatalyst under homogeneous and heterogeneous conditions can be dramatically different, highlighting that the reaction environment plays an important role in catalysis. For catalysis on solid electrodes, reactions take place in the electric double layer (EDL), where a strong electric field is experienced. In this work, empirical valence bond molecular dynamics (EVB-MD) was used to explore CO2binding in the EDL. It allows explicit descriptions of the solvent, electrolyte, catalyst–reactant, and the electrode surface material, as well as an unbiased description of the applied electric field. The strong local electric field concentrates cations, which in turn stabilizes the bound CO2. Furthermore, controlled computational experiments suggest that neither the electric field nor the cations alone can produce significant stabilization, but that the combination leads to a dramatic stabilization of the CO2 bound state.

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  • 176.
    Chen, Xiaoyu
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Theoretical Chemistry and Biology.
    Wei, Dongli
    North China Elect Power Univ, Sch Environm & Chem Engn, Beijing 102206, Peoples R China..
    Ahlquist, Mårten S. G.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Theoretical Chemistry and Biology.
    Aggregation and Significant Difference in Reactivity Therein: Blocking the CO2-to-CH3OH Reaction2021In: Organometallics, ISSN 0276-7333, E-ISSN 1520-6041, Vol. 40, no 17, p. 3087-3093Article in journal (Refereed)
    Abstract [en]

    A CoPc/CNT system has been only recently reported to transform CO2 to methanol via electrochemical reductions, despite the fact that catalyst has been studied extensively since the 1980s. The explanation of high methanol selectivity lies behind the fact that in the new report CoPc exists mainly as a monomer, while in earlier works aggregates dominate. Here, we have studied the reactivity of monomeric and dimeric CoPc by DFT. The mechanism involves rate-limiting CO2 association, with the C-O cleavage step having very similar activation free energy. Once the Co-CO-intermediate is formed, the reaction bifurcates with two possible paths: (1) CO dissociation or (2) one additional reduction follows a protonation to give the Co-CHO-intermediate, which then leads to methanol by further reactions. For the monomeric species at low reduction potentials, CO dissociation is favored, but the formation of Co-CHO-becomes competitive at more negative applied potentials. For the dimer, the CO dissociation is always favored, and the reduction needed to form the C-H bond is negative enough for it not to be observed. The more difficult reduction stems from repulsive interactions between the CoPc units and lower solvent stabilization of the charge in the aggregate.

  • 177.
    Chen, Xing
    et al.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry.
    Rinkevicius, Zilvinas
    KTH, School of Biotechnology (BIO), Theoretical Chemistry.
    Cao, Zexing
    Department of Chemistry and State Key Laboratory of Physical Chemistry of Solid Surfaces, Xiamen University, China .
    Ruud, Kenneth
    Centre for Theoretical and Computational Chemistry, Department of Chemistry, University of Tromsö, Norway.
    Ågren, Hans
    KTH, School of Biotechnology (BIO), Theoretical Chemistry.
    Zero-point vibrational corrections to isotropic hyperfine coupling constants in polyatomic molecules2011In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 13, no 2, p. 696-707Article in journal (Refereed)
    Abstract [en]

    The present work addresses isotropic hyperfine coupling constants in polyatomic systems with a particular emphasis on a largely neglected, but a posteriori significant, effect, namely zero-point vibrational corrections. Using the density functional restricted-unrestricted approach, the zero-point vibrational corrections are evaluated for the allyl radical and four of its derivatives. In addition for establishing the numerical size of the zero-point vibrational corrections to the isotropic hyperfine coupling constants, we present simple guidelines useful for identifying hydrogens for which such corrections are significant. Based on our findings, we critically re-examine the computational procedures used for the determination of hyperfine coupling constants in general as well as the practice of using experimental hyperfine coupling constants as reference data when benchmarking and optimizing exchange-correlation functionals and basis sets for such calculations.

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  • 178.
    Chen, Zhihui
    et al.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry.
    Hellström, Staffan
    KTH, School of Biotechnology (BIO), Theoretical Chemistry.
    Ning, Zhijun
    KTH, School of Biotechnology (BIO), Theoretical Chemistry.
    Yu, Z-Y
    Fu, Ying
    KTH, School of Biotechnology (BIO), Theoretical Chemistry.
    Exciton Polariton Contribution to the Stokes Shift in Colloidal Quantum Dots2011In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 115, no 13, p. 5286-5293Article in journal (Refereed)
    Abstract [en]

    We study the exciton polariton contribution to the Stokes shift in colloidal quantum dots (QDs). By detailed quantum mechanical description of light-matter interaction and temporal analysis of incident electromagnetic field across the QD using the finite-difference time-domain method, we have shown that the optical excitation of an exciton in the QD and its coupling with the excitation radiation (i.e., exciton polariton) induce strong variations in the dielectric constant of the QD which contribute significantly to the Stokes shift and cause modifications 50 in the absorption spectrum that agrees well with experiments.

  • 179. Cheng, Ming
    et al.
    Yang, Xichuan
    Zhang, Fuguo
    Zhao, Jianghua
    Sun, Licheng
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Tuning the HOMO and LUMO Energy Levels of Organic Dyes with N-Carboxomethylpyridinium as Acceptor To Optimize the Efficiency of Dye-Sensitized Solar Cells2013In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 117, no 18, p. 9076-9083Article in journal (Refereed)
    Abstract [en]

    Different from traditional D-pi-A sensitizers (the traditional design concept of the organic dyes is the donor-pi-linker-acceptor structure), a series of organic dyes with pyridinium as acceptor have been synthesized in order to approach the optimal energy level composition in the TiO2-dye-iodide/triiodide system in the dye-sensitized solar cells. HOMO and LUMO energy level tuning is achieved by varying the conjugation units and the donating ability of the donor part. Detailed investigation on the relationship between the dye structure and photophysical, photoelectrochemical properties and performance of DSSCs is described. For TPA-based dyes, by substituting the 3-hexylthiophene group with a carbon-carbon double bond as pi-spacer, the bathochromic shift of absorption spectra and higher current density (J(sc)) are achieved. When the methoxyl and n-hexoxyl are introduced into CM301 to construct dyes CM302 and CM303, the absorption peak is red-shifted compared with that of CM301 due to the increase of the electron-donating ability. The devices fabricated with sensitizers CM302 and CM303 show higher J(sc) and open-circuit voltage (V-oc) than those of the device sensitized by CM301, which can be mainly attributed to the wider incident photon-to-current conversion efficiency (IPCE) response and the suppression of electron recombination between TiO2 film and electrolyte, respectively. The effects of different electron donors in DSSCs application are compared, and the results show that sensitizers with a phenothiazine (PTZ) electron-donating unit give a promising efficiency, which is even better than the TPA-based dyes. This is because the PTZ unit displayed a stronger electron-donating ability than the TPA unit (oxidation potential of 0.82 and 1.08 V vs the normal hydrogen electrode (NHE), respectively). For sensitizers CM306 and CM307, the introduction of 1,3- bis(hexyloxy)phenyl increases the donating ability of the donor part. Furthermore, the presence of long alkyl chains decreases the dye adsorption amount on the TiO2 surface, which diminishes dye aggregation and the electron recombination effectively, though, with less adsorption amount of dyes on TiO2, the device sensitized by dye CM307 obtained the best conversion efficiency of 7.1% (J(sc) = 13.6 mA.cm(-2), V-oc = 710 mV, FF = 73.6%) under AM 1.5G irradiation (100 mW.cm(-2)).

  • 180.
    Cherkasov, Artem
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Nuclear Chemistry.
    Jonsson, Mats
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Nuclear Chemistry.
    Substituent Effects on Thermochemical Properties of C-, N-, O- and S-Centered Radicals. Physical Interpretation of Substituent Effects.1999In: Journal of chemical information and computer sciences, ISSN 0095-2338, E-ISSN 1520-5142, Vol. 39, p. 1057-1063Article in journal (Refereed)
  • 181.
    Cherkasov, Artem
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Nuclear Chemistry.
    Jonsson, Mats
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Nuclear Chemistry.
    Substituent Effects on Thermochemical Properties of Free Radicals. New Substituent Scales for C-Centered Radicals1998In: Journal of chemical information and computer sciences, ISSN 0095-2338, E-ISSN 1520-5142, Vol. 38, no 6, p. 1151-1156Article in journal (Refereed)
  • 182.
    Cherkasov, Artem R
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Nuclear Chemistry.
    Jonsson, Mats
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Nuclear Chemistry.
    Galkin, Vladimir
    University of Kazan, Russia.
    A Novel Approach to the Analysis of Substituent Effects. Quantitative Description of Ionization Energies and Gas Basicity of Amines.1999In: Journal of Molecular Graphics and Modelling, ISSN 1093-3263, E-ISSN 1873-4243, Vol. 17, no 15, p. 28-42Article in journal (Refereed)
  • 183.
    Chernova, E. A.
    et al.
    Lomonosov Moscow State Univ, Dept Mat Sci, 1-73 Leninskiye Gory, Moscow 119991, Russia..
    Petukhov, D. I.
    Lomonosov Moscow State Univ, Dept Mat Sci, 1-73 Leninskiye Gory, Moscow 119991, Russia.;Lomonosov Moscow State Univ, Dept Chem, 1-3 Leninskiye Gory, Moscow 119991, Russia..
    Chumakov, A. P.
    DESY Deutsch Elekt Synchrotron, Notkestr 85, D-22607 Hamburg, Germany..
    Kirianova, A. V.
    Lomonosov Moscow State Univ, Dept Mat Sci, 1-73 Leninskiye Gory, Moscow 119991, Russia..
    Sadilov, I. S.
    Lomonosov Moscow State Univ, Dept Mat Sci, 1-73 Leninskiye Gory, Moscow 119991, Russia..
    Kapitanova, O. O.
    Lomonosov Moscow State Univ, Dept Chem, 1-3 Leninskiye Gory, Moscow 119991, Russia..
    Boytsova, O. V.
    Lomonosov Moscow State Univ, Dept Mat Sci, 1-73 Leninskiye Gory, Moscow 119991, Russia.;RAS, Kurnakov Inst Gen & Inorgan Chem, Leninsky Ave 31, Moscow 119991, Russia..
    Valeev, R. G.
    Russian Acad Sci UdmFRC UB RAS, Udmurt Fed Res Ctr, Ural Brunch, St Them Tatiana Baramzina 34, Izhevsk 426067, Russia..
    Roth, Stephan V.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Biocomposites. DESY Deutsch Elekt Synchrotron, Notkestr 85, D-22607 Hamburg, Germany..
    Eliseev, Ar A.
    Lomonosov Moscow State Univ, Dept Chem, 1-3 Leninskiye Gory, Moscow 119991, Russia..
    Eliseev, An A.
    Lomonosov Moscow State Univ, Dept Mat Sci, 1-73 Leninskiye Gory, Moscow 119991, Russia..
    The role of oxidation level in mass-transport properties and dehumidification performance of graphene oxide membranes2021In: Carbon, ISSN 0008-6223, E-ISSN 1873-3891, Vol. 183, p. 404-414Article in journal (Refereed)
    Abstract [en]

    Here we report on gas and vapor transport properties of ultra-thin graphene oxide (GO) membranes, with various C:O ratios. Graphene oxide nanosheets with an average lateral size of 800 nm and C:O ratio ranging from 2.11 to 1.81 have been obtained using improved Hummers' method by variation of graphite:KMnO4 ratio. Thin-film selective layers based on the obtained graphene oxide have been spin-coated onto porous substrates. To extend the C:O range to 2.60, thermal reduction of GO membranes was applied. A decrease in C:O ratio leads to significant water vapor permeance growth to over 60 m(3)(STP).m(-2).bar(-1).h(-1) while the permeance towards permanent gases reduces slightly. According to the permeation and sorption measurements, a decisive role of H2O diffusivity has been established, while the water sorption capacity of the graphene oxide stays nearly independent of C:O ratio in GO. The result is supported by semi-empirical modeling which reveals diminution of H2O jump activation barriers with both increasing GO interlayer spacing and its oxidation degree. The height of the activation barriers was found to vary up to an order of magnitude within the entire range of relative humidity (0-100% RH), lowering significantly for strongly oxidized GO. Our results evidence the necessity of attaining maximum GO oxidation degree for improving water transport in GO, especially at low partial pressures.

  • 184.
    Chien, Tzu-En
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Process Technology.
    Near-ambient pressure velocity map imaging2024Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Catalytic reactions on solid surfaces have been studied under Ultra-high vacuum (UHV) conditions for decades. These studies provide crucial information for catalytic reactions, such as surface structures, adsorption sites, and reaction mechanisms. However, industrial catalysis operates under high gas pressure to increase the reaction rate, so the knowledge we learn from the previous UHV studies may not be able to directly transfer to the industry. This difference is referred to as the “pressure gap”, and it represents the difficulties that scientists encounter when attempting to investigate and comprehend catalytic reactions at high pressure. To address this issue, in situ/operando techniques and instruments have been developed to study reactions at pressures closer to real-world applications.The present thesis aims to showcase the new instrument, Near-Ambient Pressure Velocity Map Imaging (NAP-VMI), and its applications to molecular spectroscopy and surface science at near-ambient pressures. This instrument features a velocity map imaging (VMI) setup with redesigned ion optics and uses differential pumping to achieve a working pressure of 10−3 mabr. It allows time-resolved measurements at microsecond time scales using the pump-probe technique with a pulsed molecular beam and a pulsed laser. The performance is validated using N2O photodissociation and N2 surface scattering. CO oxidation on Pd(110) and Pd(100) surfaces is studied at elevated oxygen pressure (1×10−5 mbar) where the surfaces reconstruct.The results show the suppression of CO2 production in oxygen rich environments for both surfaces. The difference in kinetics and dynamics behavior between the two surfaces also suggests that surface structures and adsorption sites are important in the reaction mechanisms. These findings highlight the importance of surface structure in catalytic reactions and pave the way for more effective catalysts to be designed by tailoring surface properties and reaction conditions.

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    Summary
  • 185.
    Chien, Tzu-En
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Process Technology.
    Hohmann, Lea
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Process Technology.
    Harding, Dan
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Process Technology.
    Bimodel Activity on Heterogeneous Catalysts: CO oxidation on Pd(100)Manuscript (preprint) (Other academic)
    Abstract [en]

    Time-resolved kinetics of CO oxidation on Pd(100) are studied using near-ambient pressure velocity map imaging (NAP-VMI) with a pulsed molecular beam. We observed two types of bimodel activities to CO oxidation at different oxygen exposures. To explain this behavior, we have developed two kinetic models with two different surface configurations. Three reaction channels are discovered on Pd(100) under oxygen rich environment, representing CO oxidation on different metastable surfaces. We assign those reaction channels to: CO oxidation (1) on a pristine metal surface, (2) on an epitaxial multilayer PdO(101), and (3) on a domain boundary between Pd(100) and (√5 × √5) single layer surface oxide. All reaction channels can be described in the Langmuir–Hinshelwood mechanism. This is a direct evidence of the coexistence of multiple surface activities to the CO oxidation on the Pd(100) surface. 

  • 186.
    Chien, Tzu-En
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Process Technology.
    Hohmann, Lea
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Process Technology.
    Harding, Dan
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Process Technology.
    Time-Resolved Surface Reaction Kinetics in the Pressure GapManuscript (preprint) (Other academic)
    Abstract [en]

    We extend the use of our recently developed Near-Ambient Pressure Velocity Map Imaging (NAP-VMI) technique to study the kinetics and dynamics of catalytic reactions in the pressure gap. As an example, we show that NAP-VMI combined with molecular beam surface scattering allows the direct measurement of time- and velocity-resolved kinetics of the scattering and oxidation of CO on the Pd(110) surface with oxygen pressures at the surface up to 1× 10−5 mbar, where different metastable surface structures form. Our results show that the c(2×4) oxide structure formed at low O2 pressure is highly active for CO oxidation. The velocity distribution of the CO2 products shows the presence of two reaction channels, which we attributeto reactions starting from two distinct but rapidly interconverting CO binding sites. The effective CO oxidationreaction activation energy is Er = (1.0 ± 0.13) eV. The CO2 production is suppressed at higher O2 pressure due to the number of antiphase domain boundaries increases, and the missing row sites are filled by O–atoms at O2 pressures approaching 1× 10−6 mbar. Filling of these sites by O–atoms reduces the CO surface lifetime, meaningthe surface oxide is inactive for CO oxidation. We briefly outline further developments planned for the NAP-VMI and its application to other types of experiments.

  • 187.
    Chmyrov, Andriy
    KTH, School of Engineering Sciences (SCI), Applied Physics, Experimental Biomolecular Physics.
    Photo-induced dark states influorescence spectroscopy – investigations & applications2010Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis focuses on investigations of transient dark states of fluorescentmolecules using spectroscopic techniques. The main purpose is to show andconvince the reader that transient dark states are not always a nuisance, butalso represent an additional source of information. Several studies with fluorescencecorrelation spectroscopy were performed, all related to non-fluorescentstates such as triplet state or isomerized states.Photobleaching is one of the main problems in virtually all of the fluorescencetechniques. In this thesis, mechanisms that retard photobleaching arecharacterized. Several compounds, antioxidants and triplet state quenchers,which decrease photobleaching, are studied, and guidelines for achieving optimalfluorescence brightness using these compounds are presented.Triplet state quenching by several compounds was studied. Detailed investigationsof the fluorescence quencher potassium iodide demonstratedthat for some of fluorophores, except of quenching, there is fluorescence enhancementmechanism present. In agreement with the first publication inthis thesis, antioxidative properties were found to play an important role inthe fluorescence enhancement. Quenching of the triplet state is proposedas a tool for monitoring diffusion mediated reactions over a wide range offrequencies.Specially designed fluorophores combining high triplet yields with reasonablefluorescence brightness and photostability were characterized forpossible applications in novel super-resolution imaging techniques based onfluorescence photoswitching. Except of benefits for imaging techniques, photoinducedswitching to non-fluorescent states could be used for monitoringmolecular diffusion, which was also demonstrated in this thesis.Studies of the triplet state kinetics of fluorophores close to dielectric interfaceswere performed using fluorescence spectroscopy. The analysis of thetriplet state kinetic can provide information about the local microenvironmentand electrostatic interactions near dielectric interfaces.

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    AndriyChmyrov-PhDthesis
  • 188.
    Chmyrov, Andriy
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Experimental Biomolecular Physics.
    Arden-Jacob, Jutta
    ATTO-TEC GmbH, Germany.
    Zilles, Alexander
    University of Siegen, Germany.
    Drexhage, Karl-Heinz
    University of Siegen, Germany.
    Widengren, Jerker
    KTH, School of Engineering Sciences (SCI), Applied Physics, Experimental Biomolecular Physics.
    Characterization of new fluorescent labels for ultra-high resolution microscopy2008In: Photochemical and Photobiological Sciences, ISSN 1474-905X, E-ISSN 1474-9092, Vol. 7, no 11, p. 1378-1385Article in journal (Refereed)
    Abstract [en]

    Photo-induced switching of dyes into dark, long-lived states, such as a triplet state, has recently gained increasing interest, as a means to achieve ultra-high optical resolution. Additionally, these long lived states are often highly environment-sensitive and their photodynamics can thus offer additional independent fluorescence-based information. However, although providing a useful mechanism for photo-induced switching, the triplet state often appears as a precursor state for photobleaching, which potentially can limit its usefulness. In this work, a set of rhodamine and pyronin dyes, modified by substitution of heavy atoms and nitrogen within or close to the central xanthene unit of the dyes, were investigated with respect to their triplet state dynamics and photostabilities, under conditions relevant for ultra-high resolution microscopy. Out of the dyes investigated, in particular the rhodamine and pyronin dyes with a sulfur atom replacing the central oxygen atom in the xanthene unit were found to meet the requirements for ultra-high resolution microscopy, combining a prominent triplet state yield with reasonable photostability.

  • 189.
    Chmyrov, Andriy
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Experimental Biomolecular Physics.
    Sandén, Tor
    KTH, School of Engineering Sciences (SCI), Applied Physics, Experimental Biomolecular Physics.
    Widengren, Jerker
    KTH, School of Engineering Sciences (SCI), Applied Physics, Experimental Biomolecular Physics.
    Iodide as a Fluorescence Quencher and Promoter-Mechanisms and Possible Implications2010In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 114, no 34, p. 11282-11291Article in journal (Refereed)
    Abstract [en]

    In this work, fluorescence correlation spectroscopy (FCS) was used to investigate the effects of potassium iodide (KI) on the electronic-state population kinetics of a range of organic dyes in the visible wavelength range. Apart from a heavy atom effect promoting intersystem crossing to the triplet states in all dyes, KI was also found to enhance the triplet-state decay rate by a charge-coupled deactivation. This deactivation was only found for dyes with excitation maximum in the blue range, not for those with excitation maxima at wavelengths in the green range or longer. Consequently, under excitation conditions sufficient for triplet state formation, KI can promote the triplet state buildup of one dye and reduce it for another, red-shifted dye. This anticorrelated, spectrally separable response of two different dyes to the presence of one and the same agent may provide a useful readout for biomolecular interaction and microenvironmental monitoring studies. In contrast to the typical notion of KI as a fluorescence quencher, the FCS measurements also revealed that when added in micromolar concentrations KI can act as an antioxidant, promoting the recovery of photo-oxidized fluorophores. However, in millimolar concentrations KI also reduces intact, fluorescently viable fluorophores to a considerable extent. In aqueous solutions, for the dye Rhodamine Green, an optimal concentration of KI of approximately 5 mM can be defined at which the fluorescence signal is maximized. This concentration is not high enough to allow full triplet state quenching. Therefore, as a fluorescence enhancement agent, it is primarily the antioxidative properties of KI that play a role.

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    Chmyrov et al J Phys Chem B 2010
  • 190.
    Chmyrov, Andriy
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Experimental Biomolecular Physics.
    Sandén, Tor
    KTH, School of Engineering Sciences (SCI), Applied Physics, Experimental Biomolecular Physics.
    Widengren, Jerker
    KTH, School of Engineering Sciences (SCI), Applied Physics, Experimental Biomolecular Physics.
    Iodide as a Triplet State Promoter and Quencher –Mechanisms and Possible ImplicationsManuscript (preprint) (Other academic)
    Abstract [en]

    In this work, Fluorescence Correlation Spectroscopy(FCS) was used to investigate the effects of potassium iodide(KI) on the electronic state population kinetics of arange of organic dyes in the visible wavelength range. Apartfrom a heavy atom effect promoting intersystem crossing tothe triplet states in all dyes, KI was also found to enhancethe triplet state decay by a charge-coupled deactivation.This deactivation was only found for dyes with excitationmaximum in the blue range, not for those with excitationmaxima at wavelengths in the green range or longer. Consequently,under excitation conditions sufficient for tripletstate formation, KI can promote the triplet state build-up ofone dye and reduce it for another, red-shifted dye. The anticorrelated,spectrally separable responses of two dyes to thepresence of one and the same agent are likely to provide auseful readout for biomolecular interaction and micro-environmentalmonitoring studies. In contrast to the typicalnotion of KI as a fluorescence quencher, the FCS measurementsalso revealed that when added in micromolar concentrationsKI can act as an anti-oxidant, promoting the recoveryof photo-oxidized fluorophores. However, in millimolarconcentrations KI also reduces intact, fluorescently viablefluorophores to a considerable extent. In aqueous solutions,an optimal concentration of KI of approximately 5 mM canbe defined at which the fluorescence signal is maximized.This concentration is not high enough to allow full tripletstate quenching. Therefore, as a fluorescence enhancementagent, it is primarily the anti-oxidative properties of KI thatplay a role.

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    AndriyChmyrov-KI
  • 191.
    Chmyrov, Andriy
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Experimental Biomolecular Physics.
    Sandén, Tor
    KTH, School of Engineering Sciences (SCI), Applied Physics, Experimental Biomolecular Physics.
    Widengren, Jerker
    KTH, School of Engineering Sciences (SCI), Applied Physics, Experimental Biomolecular Physics.
    Recovery of Photoinduced Reversible Dark States Utilized for Molecular Diffusion Measurements2010In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 82, no 24, p. 9998-10005Article in journal (Refereed)
    Abstract [en]

    For a spatially restricted excitation volume, the effective modulation of the excitation in time is influenced by the passage times of the molecules through the excitation volume. By applying an additional time-modulated excitation, the buildup of photoinduced reversible dark states in fluorescent molecules can be made to vary significantly with their passage times through the excitation volume. The variations in the dark state populations are reflected by the time-averaged fluorescence intensity, which thus can be used to characterize the mobilities of the molecules. The concept was experimentally verified by measuring the fluorescence response of freely diffusing cyanine fluorophores (Cy5), undergoingtrans-cis isomerization when subject to time-modulated excitation in a focused laser beam. From the fluorescence response, and by applying a simple photodynamic model, the transition times of the Cy5 molecules could be well reproduced when applying different laminar flow speeds through the detection volume. The presented approach puts no constraints on sample concentration, no requirements for high time resolution or sensitivity in the detection, nor requires a high fluorescence brightness of the characterized molecules. This can make the concept useful for a broad range of biomolecular mobility studies.

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    fulltext
  • 192.
    Choubey, Sandhya
    et al.
    KTH, School of Engineering Sciences (SCI), Physics. HBNI.
    Dutta, Debajyoti
    HBNI, Harish Chandra Res Inst, Chhatnag Rd, Allahabad 211019, Uttar Pradesh, India..
    Pramanik, Dipyaman
    HBNI, Harish Chandra Res Inst, Chhatnag Rd, Allahabad 211019, Uttar Pradesh, India..
    Measuring the sterile neutrino CP phase at DUNE and T2HK2018In: European Physical Journal C, ISSN 1434-6044, E-ISSN 1434-6052, Vol. 78, no 4, article id 339Article in journal (Refereed)
    Abstract [en]

    The CP phases associated with the sterile neutrino cannot be measured in the dedicated short-baseline experiments being built to test the sterile neutrino hypothesis. On the other hand, these phases can be measured in long-baseline experiments, even though the main goal of these experiments is not to test or measure sterile neutrino parameters. In particular, the sterile neutrino phase delta(24) affects the charged-current electron appearance data in long-baseline experiment. In this paper we show how well the sterile neutrino phase delta(24) can be measured by the next-generation long-baseline experiments DUNE, T2HK (and T2HKK). We also show the expected precision with which this sterile phase can be measured by combining the DUNE data with data from T2HK or T2HKK. The T2HK experiment is seen to be able to measure the sterile phase delta(24) to a reasonable precision. We also present the sensitivity of these experiments to the sterile mixing angles, both by themselves, as well as when DUNE is combined with T2HK or T2HKK.

  • 193. Choudhuri, I.
    et al.
    Patra, N.
    Mahata, A.
    Ahuja, Rajeev
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics. Department of Physics and Astronomy, Uppsala University, Uppsala, Sweden.
    Pathak, B.
    B-N@Graphene: Highly Sensitive and Selective Gas Sensor2015In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 119, no 44, p. 24827-24836Article in journal (Refereed)
    Abstract [en]

    We have performed density functional theory (DFT) calculations to study the gas (CO, CO2, NO, and NO2) sensing mechanism of pure and doped (B, N, and B-N) graphene surfaces. The calculated adsorption energies of the various toxic gases (CO, CO2, NO, and NO2) on the pure and doped graphene surfaces show, doping improves adsorption energy and selectivity. The electronic properties of the B-Ngraphene surfaces change significantly compared to pure and B and Ngraphene surfaces, while selective gas molecules are adsorbed. So, we report B-N codoping on graphene can be highly sensitive and selective for semiconductor-based gas sensor.

  • 194. Cifelli, Mario
    et al.
    Domenici, Valentina
    Dvinskikh, Sergey V.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry.
    Glogarova, Milada
    Veracini, Carlo Alberto
    Translational self-diffusion in the synclinic to anticlinic phases of a ferroelectric liquid crystal2010In: SOFT MATTER, ISSN 1744-683X, Vol. 6, no 23, p. 5999-6003Article in journal (Refereed)
    Abstract [en]

    In this work, the first direct measurement of inter and intra-layer molecular self-diffusion in the smectic phases of a chiral smectogen (S)-2-methylbutyl-[4'-(4 ''-heptyloxyphenyl)-benzoyl-4-oxy-(S)-2-((S)-2')benzoyl)-propionyl)]-pro pionate (ZLL7/*) by means of pulsed field gradient NMR is reported. Self-diffusion coefficients as low as 10(-13) m(2) s(-1) have been measured by combining magic echo spin decoupling with a stimulated echo sequence. The transitions among synclinic-anticlinic smectic phases are associated with a change in the self-diffusion coefficients.

  • 195. Cifelli, Mario
    et al.
    Domenici, Valentina
    Dvinskikh, Sergey V.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Veracini, Carlo Alberto
    Zimmermann, Herbert
    Translational self-diffusion in the smectic phases of ferroelectric liquid crystals: an overview2012In: Phase Transitions, ISSN 0141-1594, E-ISSN 1029-0338, Vol. 85, no 10, p. 861-871Article in journal (Refereed)
    Abstract [en]

    In this work, we present our recent results obtained in the field of translational self-diffusion studies by means of H-1 NMR diffusometry in smectic phases formed by calamitic chiral liquid crystals. In particular, the diffusional behavior of chiral smectic phases with different clinicity, such as the ferroelectric and antiferroelectric phases, will be discussed on the basis of the results obtained on three different chiral smectogens. This research demonstrates that, despite previous assertions, out-of-plane translational diffusion in smectic phases is poorly affected by the clinicity of the phases, showing no discontinuity at the transition from synclinic to anticlinic structures, typical of the smectic C* phases. We can conclude that diffusion basically reflects the layered smectic structure where in-plane diffusion is much faster and less hindered than the out-of-plane one.

  • 196.
    Claesson, Per M.
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Makuska, R.
    Varga, I.
    Meszaros, R.
    Titmuss, S.
    Linse, P.
    Pedersen, J. Skov
    Stubenrauch, Cosima
    Bottle-brush polymers: Adsorption at surfaces and interactions with surfactants2010In: Advances in Colloid and Interface Science, ISSN 0001-8686, E-ISSN 1873-3727, Vol. 155, no 1-2, p. 50-57Article in journal (Refereed)
    Abstract [en]

    Solution and adsorption properties of both charged and uncharged bottle-brush polymers have been investigated. The solution conformation and interactions in solution have been investigated by small-angle scattering techniques. The association of the bottle-brush polymers with anionic surfactants has also been studied. Surfactant binding isotherm measurements, NMR, surface tension measurements, as well as SAXS, SANS and light scattering techniques were utilized for understanding the association behaviour in bulk solutions. The adsorption of the bottle-brush polymers onto oppositely charged surfaces has been explored using a battery of techniques, including reflectometry, ellipsometry, quartz crystal microbalance, and neutron reflectivity. The combination of these techniques allowed determination of adsorbed mass, layer thickness, water content, and structural changes occurring during layer formation. The adsorption onto mica was found to be very different to that on silica, and an explanation for this was sought by employing a lattice mean-field theory. The model was able to reproduce a number of salient experimental features characterizing the adsorption of the bottle-brush polymers over a wide range of compositions, spanning from uncharged bottle-brushes to linear polyelectrolytes. This allowed us to shed light on the importance of electrostatic surface properties and non-electrostatic surface-polymer affinity for the adsorption. The interactions between bottle-brush polymers and anionic surfactants in adsorbed layers have also been elucidated using ellipsometry, neutron reflectivity and surface force measurements.

  • 197.
    Claesson, Per M.
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Poptoshev, Evgeni
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Blomberg, Eva
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Dedinaite, Andra
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Polyelectrolyte-mediated surface interactions2005In: Advances in Colloid and Interface Science, ISSN 0001-8686, E-ISSN 1873-3727, Vol. 114, p. 173-187Article, review/survey (Refereed)
    Abstract [en]

    The current understanding of interactions between surfaces coated with polyelectrolytes is reviewed. Experimental data obtained with various surface force techniques are reported and compared with theoretical predictions. The majority of the studies concerned with interactions between polyelectrolyte-coated surfaces deal with polyelectrolytes adsorbed to oppositely charged surfaces, and this is also the main focus of this review. However, we also consider polyelectrolytes adsorbed to uncharged surfaces and to similarly charged surfaces, areas where theoretical predictions are available, but relevant experimental data are mostly lacking. We also devote sections to interactions between polyelectrolyte brush-layers and to interactions due to non-adsorbing polyelectrolytes. Here, a sufficient amount of both theoretical and experimental studies are reported to allow us to comment on the agreement between theory and experiments. A topic of particular interest is the presence of trapped non-equilibrium states that often is encountered in experiments, but difficult to treat theoretically.

  • 198.
    Claesson, Per
    et al.
    KTH, Superseded Departments (pre-2005), Chemistry.
    Poptochev, Evgeni
    KTH, Superseded Departments (pre-2005), Chemistry.
    Blomberg, Eva
    KTH, Superseded Departments (pre-2005), Chemistry.
    Surface Forces and Emulsion Stability2004In: Food Emulsions / [ed] Sjöblom, J., Friberg, S. and Larsson, K., New York: Marcel Dekker, 2004, 4, p. 257-297Chapter in book (Other academic)
  • 199.
    Cooper, Thomas M.
    et al.
    Air Force Res Lab, Mat & Mfg Directorate, Dayton, OH 45433 USA..
    Haley, Joy E.
    Air Force Res Lab, Mat & Mfg Directorate, Dayton, OH 45433 USA..
    Stewart, David J.
    Air Force Res Lab, Mat & Mfg Directorate, Dayton, OH 45433 USA..
    Long, Stephanie
    Air Force Res Lab, Mat & Mfg Directorate, Dayton, OH 45433 USA..
    Krein, Douglas M.
    Air Force Res Lab, Mat & Mfg Directorate, Dayton, OH 45433 USA..
    Burke, Aaron R.
    Air Force Res Lab, Mat & Mfg Directorate, Dayton, OH 45433 USA..
    Arias, Eduardo
    Ctr Invest Quim Aplicada CIQA, Blvd Enrique Reyna 140, Saltillo 25294, Coahuila, Mexico..
    Moggio, Ivana
    Ctr Invest Quim Aplicada CIQA, Blvd Enrique Reyna 140, Saltillo 25294, Coahuila, Mexico..
    Turlakov, Gleb
    Ctr Invest Quim Aplicada CIQA, Blvd Enrique Reyna 140, Saltillo 25294, Coahuila, Mexico..
    Ziolo, Ronald F.
    Ctr Invest Quim Aplicada CIQA, Blvd Enrique Reyna 140, Saltillo 25294, Coahuila, Mexico..
    Biler, Michal
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Theoretical Chemistry and Biology.
    Linares, Mathieu
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Theoretical Chemistry and Biology.
    Norman, Patrick
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Theoretical Chemistry and Biology.
    Nanoscale Organization of a Platinum(II) Acetylide Cholesteric Liquid Crystal Molecular Glass for Photonics Applications2020In: Advanced Functional Materials, ISSN 1616-301X, E-ISSN 1616-3028, Vol. 30, no 28, article id 1910562Article in journal (Refereed)
    Abstract [en]

    The fabrication, molecular structure, and spectroscopy of a stable cholesteric liquid crystal platinum acetylide glass obtained from trans-Pt(PEt3)(2)(C(sic)C-C6H5-C(sic)N)(C(sic)C-C6H5-COO-Cholesterol), are described and designated as PE1-CN-Chol. Polarized optical microscopy, differential scanning calorimetry, and wide-angle X-ray scattering experiments show room temperature glassy/crystalline texture with crystal formation upon heating to 165 degrees C. Further heating results in conversion to cholesteric phase. Cooling to room temperature leads to the formation of a cholesteric liquid crystal glass. Scanning tunneling microscopy of a PE1-CN-Chol monolayer reveals self-assembly at the solid-liquid interface with an array of two molecules arranged in pairs, oriented head-to-head through the CN groups, giving rise to a lamella arrangement. The lamella structure obtained from molecular dynamics calculations shows a clear phase separation between the conjugated platinum acetylide and the hydrophobic cholesterol moiety with the lamellae separation distance being 4.0 nm. Ultrafast transient absorption and flash photolysis spectra of the glass show intersystem crossing to the triplet state occurring within 100 ps following excitation. The triplet decay time of the film compared to aerated and deoxygenated solutions is consistent with oxygen quenching at the film surface but not within the film. The high chromophore concentration, high glass thermal stability, and long triplet lifetime in air show that these materials have potential as nonlinear absorbing materials.

  • 200. Costa e Silva, Andre
    et al.
    Ågren, John
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Physical Metallurgy.
    Clavaguera-Mora, Maria Teresa
    Djurovic, D.
    Gomez-Acebo, Tomas
    Lee, Byeong-Joo
    Liu, Zi-Kui
    Miodownik, Peter
    Seifert, Hans Juergen
    Applications of computational thermodynamics - the extension from phase equilibrium to phase transformations and other properties2007In: Calphad, ISSN 0364-5916, E-ISSN 1873-2984, Vol. 31, no 1, p. 53-74Article in journal (Refereed)
    Abstract [en]

    Complex equilibria and phase transformations involving diffusion can now be calculated quickly and efficiently. Detailed examples are given for cases which involve varying degrees of non-equilibrium and therefore time-dependence. Despite very good agreement between such calculations and experimental results, many potential end-users are still not convinced that such techniques could be usefully applied to their own specific problems. Friendly graphic interface versions of calculating software are now generally available, so the authors conclude that the most likely source of the reluctance to use such tools lies in the formulation of relevant questions and the interpretation of the results. Although the potential impact of such tools was foreseen many years ago [M. Hillert, Calculation of phase equilibria, in: Conference on Phase Transformations, 1968], few changes in the relevant teaching curricula have taken into account the availability and power of such techniques. This paper has therefore been designed not only as a collection of interesting problems, but also highlights the critical steps needed to achieve a solution. Each example includes a presentation of the "real" problem, any simplifications that are needed for its solution, the adopted thermodynamic formulation, and a critical evaluation of the results. The availability of such examples should facilitate changes in subject matter that will both make it easier for the next generation of students to use these tools, and at the same time reduce the time and effort currently needed to solve such problems by less efficient methods. The first set of detailed examples includes the deoxidation of steel by aluminum; heat balance calculations associated with ladle additions to steel; the determination of conditions that avoid undesirable inclusions; the role of methane in sintering atmospheres; interface control during the physical vapour deposition of cemented carbide; oxidation of gamma-TiAl materials; and simulation of the thermolysis of metallorganic precursors for Si-C-N ceramics and interface reaction of yttrium silicates with SiC-coated C/C-SiC composites for heat shield applications. A second set of examples, more dependent on competitive nucleation and growth, includes segregation and carburization in multicomponent steels and features a series of sophisticated simulatons using DICTRA software. Interfacial and strain energies become increasingly important in defining phase nucleation and morphology in such problems, but relatively little information is available compared to free energy and diffusion databases. The final section therefore demonstrates how computational thermodynamics, semi-empirical atomistic approaches and first-principles calculations are being used to aid filling this gap in our knowledge. (c) 2006 Elsevier Ltd. All rights reserved.

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