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  • 251. Ganguly, Pritam
    et al.
    Schravendijk, Pim
    Hess, Berk
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Theoretical & Computational Biophysics. Technische Universität Darmstadt, Germany; Stockholm University, Sweden .
    van der Vegt, Nico F. A.
    Ion Pairing in Aqueous Electrolyte Solutions with Biologically Relevant Anions2011In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 115, no 13, p. 3734-3739Article in journal (Refereed)
    Abstract [en]

    We performed molecular simulations to study ion pairing in aqueous solutions. Our results indicate that ion specific interactions of Li+, Na+, and K+ with the dimethyl phosphate anion are solvent-mediated. The same mechanism applies to carboxylate ions, as has been illustrated in earlier simulations of aqueous alkali acetate solutions. Contact ion pairs play only a minor role or no role at all in determining the solution structure and ion specific thermodynamics of these systems. On the basis of the Kirkwood Buff theory of solution we furthermore show that the well-known reversal of the Hofmeister series of salt activity coefficients, comparing chloride or bromide with dimethyl phosphate or acetate, is caused by changing from a contact pairing mechanism in the former system to a solvent-mediated interaction mechanism in the latter system.

  • 252.
    Gao, Jiajia
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Crystallography as forensic tool for electrolyte degradation in dye-sensitized solar cellsManuscript (preprint) (Other academic)
  • 253.
    Gao, Jiajia
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Electrolyte-Based Dynamics: Fundamental Studies for Stable Liquid Dye-Sensitized Solar Cells2016Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The long-term outdoor durability of dye-sensitized solar cells (DSSCs) is still a challenging issue for the large-scale commercial application of this promising photovoltaic technique. In order to study the degradation mechanism of DSSCs, ageing tests under selected accelerating conditions were carried out. The electrolyte is a crucial component of the device. The interactions between the electrolyte and other device components were unraveled during the ageing test, and this is the focus of this thesis. The dynamics and the underlying effects of these interactions on the DSSC performance were studied.

    Co(bpy)32+/3+-mediated solar cells sensitized by triphenylamine-based organic dyes are systems of main interest. The changes with respect to the configuration of both labile Co(bpy)32+ and apparently inert Co(bpy)33+ redox complexes under different ageing conditions have been characterized, emphasizing the ligand exchange problem due to the addition of Lewis-base-type electrolyte additives and the unavoidable presence of oxygen. Both beneficial and adverse effects on the DSSC performance have been separately discussed in the short-term and long-term ageing tests. The stability of dye molecules adsorbed on the TiO2 surface and dissolved in the electrolyte has been studied by monitoring the spectral change of the dye, revealing the crucial effect of cation-based additives and the cation-dependent stability of the device photovoltage. The dye/TiO2 interfacial electron transfer kinetics were compared for the bithiophene-linked dyes before and after ageing in the presence of Lewis base additives; the observed change being related to the light-promoted and Lewis-base-assisted performance enhancement. The effect of electrolyte co-additives on passivating the counter electrode was also observed. The final chapter shows the effect of electrolyte composition on the electrolyte diffusion limitation from the perspectives of cation additive options, cation concentration and solvent additives respectively. Based on a comprehensive analysis, suggestions have been made regarding lithium-ion-free and polymer-in-salt strategies, and also regarding cobalt complex degradation and the crucial role of Lewis base additives. The fundamental studies contribute to the understanding of DSSC chemistry and provide a guideline towards achieving efficient and stable DSSCs.

  • 254.
    Gao, Jiajia
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Impedance spectroscopic analysis of electrolyte diffusion in aged dye-sensitized solar cells containing cobalt tris(bipyridine) redox shuttlesManuscript (preprint) (Other academic)
  • 255.
    Gao, Jiajia
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Interfacial dye/electrolyte interaction dramatically improving the photocurrent in dye-sensitized solar cellsManuscript (preprint) (Other academic)
  • 256.
    Gao, Jiajia
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Light-induced cobalt tris(bipyridine) ligand exchange: a simple strategy towards efficient and durable dye-sensitized solar cellsManuscript (preprint) (Other academic)
  • 257.
    Gao, Jiajia
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Yang, W.
    Pazoki, M.
    Boschloo, G.
    Kloo, Lars
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Cation-Dependent Photostability of Co(II/III)-Mediated Dye-Sensitized Solar Cells2015In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 119, no 44, p. 24704-24713Article in journal (Refereed)
    Abstract [en]

    The electrolyte composition has a significant effect on the performance and stability of cobalt-based, dye-sensitized solar cells (DSSCs). The stability of DSSCs incorporating Co(II/III) tris(bipyridine) redox mediator has been investigated over 1000 h under full solar irradiation (with UV cutoff) at a temperature of 60 °C, the main focus being on monitoring the photovoltaic performance of the device and analyzing the internal charge-transfer dynamics in the presence of different cation coadditives (preferably added as tetracyanoborate salts). A clear cation-dependence is shown, not only of the early light-induced performance but also of the long-term photostability of the photovoltage of the device. These light-induced changes, which are attributed to the promotion of electron injection and less electron recombination loss, by transient spectral and electrochemical studies at the TiO2/dye/electrolyte interface, indicate that the main cation effects involve the TiO2 surface electric field and energy-state distribution. By examining the stability of adsorbed and solvated dye during aging, it has been found that the dye photodegradation is probably responsible for the decline in the photovoltage and that this is extremely dependent on the nature of the cation coadditives in the electrolyte. It is therefore suggested that optimization of the electrolyte cation composition is essential for improving the stability of cobalt-based DSSCs.

  • 258.
    Gao, Jiajia
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Yang, Wenxing
    Uppsala Univ, Angstrom Lab, Dept Chem, Box 523, SE-75120 Uppsala, Sweden..
    El-Zohry, Ahmed M.
    Uppsala Univ, Angstrom Lab, Dept Chem, Box 523, SE-75120 Uppsala, Sweden..
    Prajapati, Govind Kumar
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Fang, Yuan
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Dai, Jing
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Hao, Yan
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Leandri, Valentina
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Svensson, Per H.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry. RISE Surface Proc Formulat, Forskargatan 20j, SE-15136 Sodertalje, Sweden..
    Furo, Istvan
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Boschloo, Gerrit
    Uppsala Univ, Angstrom Lab, Dept Chem, Box 523, SE-75120 Uppsala, Sweden..
    Lund, Torben
    Roskilde Univ, Dept Sci & Environm, DK-4000 Roskilde, Denmark..
    Kloo, Lars
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Light-induced electrolyte improvement in cobalt tris(bipyridine)-mediated dye-sensitized solar cells2019In: Journal of Materials Chemistry A, ISSN 2050-7488, Vol. 7, no 33, p. 19495-19505Article in journal (Refereed)
    Abstract [en]

    Lithium-ion-free tris(2,2 '-bipyridine) Co(ii/iii)-mediated electrolytes have previously been proposed for long-term stable dye-sensitized solar cells (DSSCs). Such redox systems also offer an impressive DSSC performance improvement under light soaking exposure, manifested by an increase in photocurrent and fill factor without the expense of decreasing photovoltage. Kinetic studies show that charge transfer and ion diffusion at the electrode/electrolyte interface are improved due to the light exposure. Control experiments reveal that the light effect is unambiguously associated with electrolyte components, [Co(bpy)(3)](3+) and the Lewis-base additive tert-butylpyridine (TBP). Electrochemical and spectroscopic investigation of the [Co(bpy)(3)](3+)/TBP mixtures points out that the presence of TBP, which retards the electrolyte diffusion, however causes an irreversible redox reaction of [Co(bpy)(3)](3+) upon light exposure that improves the overall conductivity. This discovery not only provides a new strategy to mitigate the typical J(sc)-V-oc trade-off in Co(ii/iii)-mediated DSSCs but also highlights the importance of investigating the photochemistry of a photoelectrochemical system.

  • 259.
    Gao, Li
    et al.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Tu, Yaoquan
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Ågren, Hans
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Eriksson, Leif A.
    Characterization of Agonist Binding to His524 in the Estrogen Receptor alpha Ligand Binding Domain2012In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 116, no 16, p. 4823-4830Article in journal (Refereed)
    Abstract [en]

    The bioactivities of the natural steroidal estrogen 17 beta-estradiol (E-2), the synthetic estrogen diethylstilbestrol (DES), and the phytoestrogen genistein (GEN) are intimately associated with their binding to the estrogen receptor alpha ligand binding domain (ER alpha LBD) and accordingly allostery. Molecular modeling techniques have been performed on agonists in complex with the LBD, focusing on the pivotal role of His524 modeled as the epsilon-tautomer and the protonated form (depending on pH). It is found that E-2 binds to the active LBD with the aid of Leu525, showing existing stable patterns of an H-binding network with Glu419 via His524 in all models. The main difference seen in the effect is that the full agonists E-2 and DES have higher binding energies to the protonated His524 than the partial agonists GEN and Way-169916 (W), which is in line with noted experimental transcriptional activities. In conclusion, the study demonstrates that the phytoestrogen GEN interacts differently with the LBD than what E-2 and DES do, which explains the observed signaling differences.

  • 260.
    Gao, Li
    et al.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Tu, Yaoquan
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Ågren, Hans
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Eriksson, Leif A.
    Modification of the anticancerdrug tamoxifen to avoid CYP2D6 polymorphismManuscript (preprint) (Other academic)
  • 261. Gao, Yan
    et al.
    Zhang, Linlin
    Ding, Xin
    Sun, Licheng
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Artificial photosynthesis - functional devices for light driven water splitting with photoactive anodes based on molecular catalysts2014In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 16, no 24, p. 12008-12013Article in journal (Refereed)
    Abstract [en]

    Photoactive anodes consisting of Ru(bpy)(3) type photosensitizer 1 and molecular catalysts 2 and 3 on nanostructured TiO2 have been assembled in functional devices for successful light driven water splitting. From their performance measurements we found that the photoanode TiO2(1 + 3) in which the molecular ruthenium catalyst and the phosphonate anchoring group are linked by a flexible -CH(2)CH(2)CH(2)chain showed a significantly higher photocurrent density than the photoanode TiO2(1 + 2) with only -CH2- linkage. The possible reasons for the different water splitting performance of otherwise identical devices are discussed.

  • 262.
    García García, Sandra
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Generation, stability and migration of montmorillonite colloids in aqueous systems2010Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    In Sweden the encapsulated nuclear waste will be surrounded by compacted bentonite in the granitic host rock. In contact with water-bearing fractures the bentonite barrier may release montmorillonite colloids that may be further transported in groundwater. If large amounts of material are eroded from the barrier, the buffer functionality can be compromised. Furthermore, in the scenario of a leaking canister, strongly sorbing radionuclides, can be transported by montmorillonite colloids towards the biosphere. This thesis addresses the effects of groundwater chemistry on the generation, stability, sorption and transport of montmorillonite colloids in water bearing rock fractures.

    To be able to predict quantities of montmorillonite colloids released from the bentonite barrier in contact with groundwater of varying salinity, generation and sedimentation test were performed. The aim is first to gain understanding on the processes involved in colloid generation from the bentonite barrier. Secondly it is to test if concentration gradients of montmorillonite colloids outside the barrier determined by simple sedimentation experiments are comparable to generation tests. Identical final concentrations and colloid size distributions were achieved in both types of tests.

    Colloid stability is strongly correlated to the groundwater chemistry. The impact of pH, ionic strength and temperature was studied. Aggregation kinetics experiments revealed that for colloid aggregation rate increased with increasing ionic strength. The aggregation rate decreased with increasing pH. The temperature effect on montmorillonite colloid stability is pH-dependent. At pH≤4, the rate constant for colloid aggregation increased with increasing temperature, regardless of ionic strength. At pH≥10, the aggregation rate constant decreased with increasing temperature. In the intermediate pH interval, the aggregation rate constant decreased with increasing temperature except at the highest ionic strength, where it increased. The relationship between the rate constant and the ionic strength allowed the critical coagulation concentration (CCC) for Na- and Ca-montmorillonite to be determined.

    In order to distinguish the contribution of physical filtration and sorption to colloid retention in transport, the different retention mechanisms were quantified. Sorption on different representative minerals in granite fractures was measured for latex colloids (50, 100, 200 nm) and montmorillonite colloids as a function of ionic strength and pH. Despite of the negative charge in mineral surfaces and colloids, sorption was detected. The sorption is correlated to the mineral point of zero charge and the zeta potential of the colloids, and increases with increasing ionic strength and decreasing pH. In transport experiments with latex colloids in columns packed with fracture filling material, the retention by sorption could clearly be seen. In particular at low flow rates, when the contact time for colloids with the mineral surfaces were the longest, sorption contributed to retention of the transport significantly. The retention of latex colloids appeared to be irreversible in contrary to the reversible montmorillonite colloid retention.

    Generation, stability and sorption of the montmorillonite colloids are controlled by electrostatic forces; hence, the results were in qualitative agreement with DLVO.

  • 263.
    Gardner, James M.
    et al.
    Johns Hopkins University.
    Abrahamsson, Maria
    Johns Hopkins University.
    Farnum, Byron H.
    Johns Hopkins University.
    Meyer, Gerald J.
    Johns Hopkins University.
    Visible Light Generation of Iodine Atoms and I-ˆ’I Bonds: Sensitized I-ˆ’ Oxidation and I3-ˆ’ Photodissociation2009In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 131, no 44, p. 16206-16214Article in journal (Refereed)
    Abstract [en]

    Direct 355 or 532 nm light excitation of TBAI3, where TBA is tetrabutyl ammonium, in CH3CN at room temperature yields an iodine atom, I?, and an iodine radical anion, I2??. In the presence of excess iodide, the iodine atom reacts quantitatively to yield a second equivalent of I2?? with a rate constant of k = 2.5 ± 0.4 ? 1010 M?1 s?1. The I2?? intermediates are unstable with respect to disproportionation and yield initial reactants, k = 3.3 ± 0.1 ? 109 M?1 s?1. The coordination compound Ru(bpz)2(deeb)(PF6)2, where bpz is 2,2?-bipyrazine and deeb is 4,4?-(C2H5CO2)2-2,2?-bipyridine, was prepared and characterized for mechanistic studies of iodide photo-oxidation in acetonitrile at room temperature. Ru(bpz)2(deeb)2+ displayed a broad metal-to-ligand charge transfer (MLCT) absorption band at 450 nm with ε = 1.7 ? 104 M?1 cm?1. Visible light excitation resulted in photoluminescence with a corrected maximum at 620 nm, a quantum yield ? = 0.14, and an excited state lifetime τ = 1.75 ?s from which kr = 8.36 ? 104 s?1 and knr = 5.01 ? 105 s?1 were abstracted. Arrhenius analysis of the temperature dependent excited state lifetime revealed an activation energy of ?2500 cm?1 and a pre-exponential factor of 1010 s?1, assigned to activated surface crossing to a ligand field or MLCT excited state. Steady state light excitation of Ru(bpz)2(deeb)2+ in a 20 mM TBAI acetonitrile solution resulted in ligand loss photochemistry with a quantum yield of 5 ? 10?5. The MLCT excited state was dynamically quenched by iodide with Ksv = 1.1 ? 105 M?1 and kq = 6.6 ± 0.3 ? 1010 M?1 s?1, a value consistent with diffusion-limited electron transfer. Excited state hole transfer to iodide was quantitative but the product yield was low due to poor cage escape yields, ?CE = 0.042 ± 0.001. Nanosecond transient absorption was used to quantify the appearance of two photoproducts [Ru(bpz?)(bpz)(deeb)]+ and I2??. The coincidence of the rate constants for [Ru(bpz?)(bpz)(deeb)]+ formation and for excited state decay indicated reductive quenching by iodide. The rate constant for the appearance of I2?? was about a factor of 3 slower than excited state decay, k = 2.4 ± 0.2 ? 1010 M?1 s?1, indicating that I2?? was not a primary photoproduct of excited state electron transfer. A mechanism was proposed where an iodine atom was the primary photoproduct that subsequently reacted with iodide, I? + I? ? I2??. Charge recombination Ru(bpz?)(bpz)(deeb)+ + I2?? ? Ru(bpz)2(deeb)2+ + 2I? was highly favored, ?Go = ?1.64 eV, and well described by a second-order equal concentration kinetic model, kcr = 2.1 ± 0.3 ? 1010 M?1 s?1.

  • 264.
    Gardner, James M
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Beyler, Maryline
    Uppsala University.
    Karnahl, Michael
    Uppsala University.
    Tschierlei, Stefanie
    Uppsala University.
    Ott, Sascha
    Uppsala University.
    Hammarström, Leif
    Uppsala University.
    Light-Driven Electron Transfer between a Photosensitizer and a Proton-Reducing Catalyst Co-adsorbed to NiO2012In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 134, no 47, p. 19322-19325Article in journal (Refereed)
    Abstract [en]

    While intermolecular hole-hopping along the surface of semiconductors is known, there are no previous examples of electron-hopping between molecules on a surface. Herein, we present the first evidence of electron transfer from the photoreduced sensitizer Coumarin-343 (C343) to complex 1, both bound on the surface of NiO. In solution, 1 has been shown to be a mononuclear Fe-based proton-reducing catalyst. The reduction of 1 is reversible and occurs within 50 ns after excitation of C343. Interfacial recombination between the reduced 1(-) and NiO hole occurs on a 100 µs time scale by non-exponential kinetics. The observed process is the first essential step in the photosensitized generation of H2 from a molecular catalyst in the absence of a sacrificial donor reagent.

  • 265.
    Gardner, James M.
    et al.
    Johns Hopkins University.
    Giaimuccio, Jovan M.
    Johns Hopkins University.
    Meyer, Gerald J.
    Johns Hopkins University.
    Evidence for Iodine Atoms as Intermediates in the Dye Sensitized Formation of I-ˆ’I Bonds2008In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 130, no 51, p. 17252-17253Article in journal (Refereed)
    Abstract [en]

    Visible light excitation of [Ru(bpz)2(deeb)](PF6)2, where bpz is 2,2?-bipyrazine and deeb is 4,4?-(CO2Et)2-2,2?-bipyridine, in acetonitrile solutions with iodide is shown to initiate excited-state electron transfer reactions that yield iodine atoms. The iodine atoms subsequently react with iodide to form the I?I bond in I2??. The resultant Ru(bpz?)(bpz)(deeb)+, I2?? stores ?1.64 eV of free energy and returns cleanly to ground-state products with kcr = (2.1 ± 0.3) ? 1010 M?1 s?1.

  • 266.
    Gardner, James M.
    et al.
    Johns Hopkins University.
    Kim, Su
    Johns Hopkins University.
    Searson, Peter C.
    Johns Hopkins University.
    Meyer, Gerald J.
    Johns Hopkins University.
    Electrodeposition of Nanometer-Sized Ferric Oxide Materials in Colloidal Templates for Conversion of Light to Chemical Energy2011In: Journal of Nanomaterials, ISSN 1687-4110, E-ISSN 1687-4129, Vol. 2011, p. 1-8Article in journal (Refereed)
    Abstract [en]

    Colloidal crystal templates were prepared by gravitational sedimentation of 0.5 micron polystyrene particles onto fluorine-doped tin oxide (FTO) electrodes. Scanning electron microscopy (SEM) shows that the particles were close packed and examination of successive layers indicated a predominantly face-centered-cubic (fcc) crystal structure where the direction normal to the substrate surface corresponds to the (111) direction. Oxidation of aqueous ferrous solutions resulted in the electrodeposition of ferric oxide into the templates. Removal of the colloidal templates yielded ordered macroporous electrodes (OMEs) that were the inverse structure of the colloidal templates. Current integration during electrodeposition and cross-sectional SEM images revealed that the OMEs were about 2 mu m thick. Comparative X-ray diffraction and infrared studies of the OMEs did not match a known phase of ferric oxide but suggested a mixture of goethite and hematite. The spectroscopic properties of the OMEs were insensitive to heat treatments at 300. C. The OMEs were utilized for photoassisted electrochemical oxidation. A sustained photocurrent was observed from visible light in aqueous photoelectrochemical cells. Analysis of photocurrent action spectra revealed an indirect band gap of 1.85 eV. Addition of formate to the aqueous electrolytes resulted in an approximate doubling of the photocurrent.

  • 267. Gaur, Sarthak
    et al.
    Johansson, Sandra
    KTH, School of Chemical Science and Engineering (CHE).
    Mohammad, Faruq
    Kumar, Challa S. S. R.
    Spivey, James J.
    Catalytic Activity of Titania-Supported Core-Shell Fe3O4@Au NanoCatalysts for CO Oxidation2012In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 116, no 42, p. 22319-22326Article in journal (Refereed)
    Abstract [en]

    In continuation of our previous work (J. Phys. Chem. Lett. 2010, 1(20), 3141 and J. Phys. Chem. C 2010, 114 (45), 19194), Fe3O4@Au core-shell types of nanoparticles were prepared by coating superparamagnetic iron oxide nanoparticles (SPIONS; similar to 4.9 nm) with a thin layer of gold (similar to 0.5 nm) and supported on microporous TiO2. To remove the ligands attached to nanoparticles, the catalyst was treated at 200, 300, 400, and 500 degrees C in either (a) a reducing atmosphere with H-2/Ar or (b) an oxidizing atmosphere with O-2/He. The synthesized nanoparticles and freshly prepared catalysts were characterized by HRTEM, which revealed that the size of the Fe3O4@Au nanoparticles was 5.34 +/- 0.71 nm and that of Fe3O4@Au/TiO2 was 5.96 +/- 0.71 nm. Fresh and pretreated programmed reduction, X-ray diffraction, X-ray photoelectron spectroscopy, and Fourier transform infrared spectroscopy. To test the activity of Fe3O4@Au/TiO2 catalysts, CO oxidation was performed over catalysts from 30 to 500 degrees C. Results showed that the catalyst treated with H-2/Ar at 500 degrees C had a lower light-off temperature and the highest CO conversion (similar to 68%) at 300 degrees C; however, such a treatment also resulted in catalyst sintering, leading to a net increase in particle size to 7.87 +/- 1.59 nm. The higher catalytic activity of the catalyst treated with H-2 at 500 degrees C can be attributed to the copresence of Fe-0 and Au-0 in the catalyst, the complete removal of organic ligands from the catalyst surface, and possibly the synergistic interaction between Au and Fe.

  • 268. Geppert, W. D.
    et al.
    Hamberg, M.
    Thomas, R. D.
    Österdahl, Fabian
    KTH, School of Engineering Sciences (SCI), Physics.
    Hellberg, F.
    Zhaunerchyk, V.
    Ehlerding, A.
    Millar, T. J.
    Roberts, H.
    Semaniak, J.
    af Ugglas, M.
    Källberg, A.
    Simonsson, A.
    Kaminska, M.
    Larsson, M.
    Dissociative recombination of protonated methanol2006In: Faraday discussions (Online), ISSN 1359-6640, E-ISSN 1364-5498, Vol. 133, p. 177-190Article in journal (Refereed)
    Abstract [en]

    The branching ratios of the different reaction pathways and the overall rate coefficients of the dissociative recombination reactions of CH3OH2+ and CD3OD2+ have been measured at the CRYRING storage ring located in Stockholm, Sweden. Analysis of the data yielded the result that formation of methanol or deuterated methanol accounted for only 3 and 6% of the total rate in CH3OH2+ and CD3OD2+, respectively. Dissociative recombination of both isotopomeres mainly involves fragmentation of the C - O bond, the major process being the three-body break-up forming CH3, OH and H (CD3, OD and D). The overall cross sections are best fitted by sigma = 1.2 +/- 0.1 x 10(-15) E-1.15 +/- 0.02 cm(2) and sigma = 9.6 +/- 0.9 x 10(-16) E-1.20 +/- 0.02 cm(2) for CH3OH2+ and CD3OD2+, respectively. From these values thermal reaction rate coefficients of k(T) = 8.9 +/- 0.9 x 10(-7) (T/300) (- 0.59 +/- 0.02) cm(3) s(-1) (CH3OH2+) and k( T) = 9.1 +/- 0.9 x 10(-7) (T/ 300) (- 0.63 +/- 0.02) cm(3) s(-1)(CD3OD2+) can be calculated. A non-negligible formation of interstellar methanol by the previously proposed mechanism via radiative association of CH3+ and H2O and subsequent dissociative recombination of the resulting CH3OH2+ ion to yield methanol and hydrogen atoms is therefore very unlikely.

  • 269. Geppert, W D
    et al.
    Thomas, R
    Ehlerding, A
    Semaniak, J
    Österdahl, Fabian
    KTH, Superseded Departments, Physics.
    af Ugglas, M
    Djuric, N
    Paal, A
    Larsson, M
    Extraordinary branching ratios in astrophysically important dissociative recombination reactions2004In: Faraday discussions (Online), ISSN 1359-6640, E-ISSN 1364-5498, Vol. 127, p. 425-437Article in journal (Refereed)
    Abstract [en]

    Branching ratios of the dissociative recombination reactions of the astrophysically relevant ions DCO+, N2H+ and DOCO+ ( as substitute for HOCO+) have been measured using the CRYRING storage ring at the Manne Siegbahn Laboratory at the University of Stockholm, Sweden. For DCO+, the channel leading to D and CO was by far the most important one ( branching ratio 0.88), only small contributions of the CD+O and OD+C product pathways ( branching ratios 0.06 each) were recorded. In the case of N2H+ the surprising result of a break-up of the N-N bond to N and NH ( branching ratio 0.64) was found with the branching ratio of the N-2+H product channel therefore displaying a branching ratio of only 0.36. In the case of DOCO+, the three-body break-up into D+O+CO dominated ( branching ratio 0.68), whereas the contribution of the CO2+H channel was only minute (0.05). The remaining share ( branching ratio 0.27) was taken by the pathway leading to OH+CO. For the dissociative recombination of N2H+ and DOCO+ also absolute reaction cross sections were obtained in the collisional energy range between 0 and 1 eV. From these cross sections it was possible to work out the thermal rate constants, which were found to be k(T) = 1.0 +/- 0.1 x 10(-7) (T/300 K)(-0.51 +/- 0.02) cm(3) s(-1) and k(T) = 1.2 +/- 0.1 x 10(-6) (T/300 K)(-0.64 +/- 0.02) cm(3) s(-1) for N2H+ and DOCO+, respectively.

  • 270. Geppert, W D
    et al.
    Thomas, R
    Hellberg, F
    Ehlerding, A
    Österdahl, Fabian
    KTH, Superseded Departments, Physics.
    af Ugglas, M
    Larsson, M
    Dissociative recombination of N2OD+2004In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 6, no 13, p. 3415-3419Article in journal (Refereed)
    Abstract [en]

    Branching ratios and absolute cross sections have been measured for the dissociative recombination of N2OD+ using the CRYRING ion storage ring. The most dominating pathways were found to be those eading to N-2 + OD (46%) and the three-body break-up producing N-2 + O + D (40%). The production of N2O is not observed. The cross section of the reaction could be fitted to the expression sigma = 1.25 +/- 0.25 x 10(-15)(E/eV)(-1.24+/-0.02), which leads to a thermal reaction rate of k(T) = 1.4 +/- 0.1 x 10(-6)(T/300)(-0.74+/-0.02) cm(3) s(-1). The findings are compared with those of the related dissociative recombination of DOCO+ as well as with earlier flowing afterglow measurements.

  • 271.
    GIERER, J
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    YANG, EQ
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Jonsson, Mats
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Nuclear Chemistry.
    REITBERGER, T
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Nuclear Chemistry.
    ON THE IMPORTANCE OF SUPEROXIDE RADICAL-ANIONS IN OXYGEN BLEACHING OF PULP1993In: Abstracts of Papers of the American Chemical Society, Vol. 205Article in journal (Refereed)
  • 272.
    Giesecke, Marianne
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Meriguet, Guillaume
    Hallberg, Fredrik
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Fang, Yuan
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Stilbs, Peter
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Furo, Istvan
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Ion association in aqueous and non-aqueous solutions probed by diffusion and electrophoretic NMR2015In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 17, no 5, p. 3402-3408Article in journal (Refereed)
    Abstract [en]

    The results of diffusion and electrophoretic NMR (eNMR) measurements are reported for a series of tetramethylammonium (TMA) electrolytes (with sulphate, fluoride, acetate, chloride, bromide, nitrate, iodide and perchlorate as anions) in deuterated solvents such as water, dimethylsulphoxide (DMSO), acetonitrile, methanol and ethanol. In addition, similar data are presented for aqueous solutions of tetraalkylammonium salts with increasing alkyl chain length. The combination of diffusion NMR and eNMR yields the effective charge for the TMA cation. Relative to the nominal charge of z(nom) = 1 of TMA, the effective charge in the different solvents is found to be progressively smaller in the order water > DMSO > methanol > acetonitrile > ethanol. A part of this observed trend is ascribed to regular ion-ion interactions incorporated in the Onsager limiting law. Indeed, in solvents with high dielectric constants such as water, DMSO and methanol, the Onsager limiting law describes well the observations for all tetraalkylammonium ions. For ethanol and acetonitrile, there is a significant difference between the experimental data and the expected limiting-law behavior that is attributed to ion association (ion pairing) not taken into consideration by the Onsager limiting law.

  • 273.
    Girdo, Valdis
    KTH, Superseded Departments, Civil and Architectural Engineering.
    Solvärmesystem för husuppvärmning i Skandinavien - Optimering1978Report (Other academic)
  • 274.
    Girdo, Valdis
    KTH, Superseded Departments, Civil and Architectural Engineering.
    Solvärmesystem för husuppvärmning i Skandinavien: Experimentella försök med plana solfångare. Jämförelse mellan beräknad och experimentellt bestämd effektivitet1978Report (Other academic)
  • 275. Goldstein, S.
    et al.
    Lind, Johan
    KTH, Superseded Departments, Chemistry.
    Merenyi, Gabor
    KTH, Superseded Departments, Chemistry.
    Reaction of organic peroxyl radicals with (NO2)-N-center dot and (NO)-N-center dot in aqueous solution: Intermediacy of organic peroxynitrate and peroxynitrite species2004In: Journal of Physical Chemistry A, ISSN 1089-5639, E-ISSN 1520-5215, Vol. 108, no 10, p. 1719-1725Article in journal (Refereed)
    Abstract [en]

    In this work, we studied the reactions of alkyl peroxyl radicals with (NO2)-N-. and (NO)-N-. using the pulse radiolysis technique. The rate constants for the reaction of (NO2)-N-. with (CH3)(2)C(OH)CH2OO., CH3OO. and c-C5H9OO. vary between 7 x 10(8) and 1.5 x 10(9) M-1 s(-1). The reaction produces relatively long-lived alkyl peroxynitrates, which are in equilibrium with the parent radicals and have no appreciable absorption above 270 nm. It is also shown that (NO)-N-. adds rapidly to (CH3)(2)C(OH)CH2OO. and CH3OO. to form alkyl peroxynitrites. The rate constants for these reactions were determined to be 2.8 x 10(9) and 3.5 x 10(9) M-1 s(-1), respectively. However, in contrast to alkyl peroxynitrates, alkyl peroxynitrites do not accumulate. Rather, they decompose rapidly via homolysis along the relatively weak O-O bond, initially forming a geminate pair. Most of this pair collapses in the cage to form an alkyl nitrate, RONO2, and about 14% diffuses out as free alkoxyl and (NO2)-N-. radicals. A thermokinetic analysis predicts the half-life of CH3OONO in water to be less than 1 mus, an estimate that agrees well with previous experimental findings of ours for other alkyl peroxynitrites. A comparison of aqueous and gaseous thermochemistry of alkyl peroxynitrates reveals that alkyl peroxyl radicals and the corresponding alkyl peroxynitrates are similarly solvated by water.

  • 276. Gorbatov, O. I.
    et al.
    Korzhavyi, Pavel A.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Technology.
    Ruban, Andrei V.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    Johansson, Börje
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    Gornostyrev, Yu. N.
    Vacancy-solute interactions in ferromagnetic and paramagnetic bcc iron: Ab initio calculations2011In: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 419, no 1-3, p. 248-255Article in journal (Refereed)
    Abstract [en]

    Vacancy-solute interactions play a crucial role in diffusion-controlled processes, such as ordering or decomposition, which occur in alloys under heat treatment or under irradiation. Detailed knowledge of these interactions is important for predicting long-term behavior of nuclear materials (such as reactor steels and nuclear-waste containers) as well as for advancing our general understanding of kinetic processes in alloys. Using first-principles calculations based on the density functional theory and employing the locally self-consistent Green's function technique, we develop a database of vacancy-solute interactions in dilute alloys of bcc Fe with 3p (Al, Si, P, S), 3d (Sc-Cu), and 4d (Y-Ag) elements. Unrelaxed interactions within the first three coordination shells have been computed in the ferromagnetic state as well as in the paramagnetic (disordered local moment) state of the iron matrix. Magnetism is found to have a strong effect on the vacancy-solute interactions. Implications of the obtained results for interpreting the effects of vacancy trapping and enhanced impurity diffusion are discussed.

  • 277.
    Gradisek, Anton
    et al.
    Jozef Stefan Inst, Dept Solid State Phys, SI-1000 Ljubljana, Slovenia..
    Cifelli, Mario
    Univ Pisa, Dipartimento Chim & Chim Ind, I-56124 Pisa, Italy..
    Wojcik, Michal
    Univ Warsaw, Dept Chem, PL-02093 Warsaw, Poland..
    Apih, Tomaz
    Jozef Stefan Inst, Dept Solid State Phys, SI-1000 Ljubljana, Slovenia..
    Dvinskikh, Sergey
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry. Lab Biomol NMR, St Petersburg 198504, Russia.
    Gorecka, Ewa
    Univ Warsaw, Dept Chem, PL-02093 Warsaw, Poland..
    Domenici, Valentina
    Univ Pisa, Dipartimento Chim & Chim Ind, I-56124 Pisa, Italy..
    Study of Liquid Crystals Showing Two Isotropic Phases by H-1 NMR Diffusometry and H-1 NMR Relaxometry2019In: CRYSTALS, Vol. 9, no 3, article id 178Article in journal (Refereed)
    Abstract [en]

    In this work, we report a study of two thermotropic liquid crystalline samples showing a not common mesophase behavior. The samples, namely a di-benzyloxy biphenyl derivative labelled 9/2 RS/RS, and a bimesogenic liquid crystal labelled L1, show a direct transition between two isotropic phases followed, at lower temperatures, by the optically isotropic, 3D structured, cubic phase. These systems have been investigated by means of H-1 NMR diffusometry and H-1 NMR relaxometry in order to characterize their isotropic-isotropic'-cubic mesophase behavior, mainly on the dynamic point of view. In particular, the temperature trend of the self-diffusion coefficients measured for both samples allowed us to significantly distinguish between the two isotropic phases, while the temperature dependence of the H-1 spin-lattice relaxation time (T-1) did not show significant discontinuities at the isotropic-isotropic' phase transition. A preliminary analysis of the frequency-dependence of H-1 T-1 at different temperatures gives information about the main motional processes active in the isotropic mesophases.

  • 278. Granas, O.
    et al.
    Korzhavyi, Pavel A.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    Kissavos, A. E.
    Abrikosov, I. A.
    Theoretical study of the Mo-Ru sigma phase2008In: Calphad, ISSN 0364-5916, E-ISSN 1873-2984, Vol. 32, no 1, p. 171-176Article in journal (Refereed)
    Abstract [en]

    The thermodynamic properties of the Mo-Ru binary sigma-phase are investigated using a combination of ab initio calculations and CALPHAD modeling. Total energy calculations have been performed for the complete set of 32 end-member compounds of a 5-sublattice compound energy model. The internal crystallographic parameters for each end-member compound have been determined by minimising the total energy. A simpler, 3-sublattice model of the Mo-Ru a-phase is formulated on the basis of calculated total energies. The site occupancy is acquired by minimising the free energy given by the compound energy model. A strong preference of Mo and Ru towards high-coordination sites and icosahedral sites in the Mo-Ru a-phase is found and analysed in terms of the electronic structure.

  • 279.
    Göthelid, Mats
    et al.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Le Lay, G.
    Karlsson, Ulf O.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    An ordered layer of molecular iodine on Ge(100) 2x12004In: Surface Science, ISSN 0039-6028, E-ISSN 1879-2758, Vol. 556, no 03-feb, p. 203-212Article in journal (Refereed)
    Abstract [en]

    Adsorption of iodine on the Ge(1 0 0) (2 x 1) surface has been investigated by core level and valence band photoelectron spectroscopy and scanning tunnelling microscopy. Iodine binds to dimer atom dangling bonds without disrupting the dimers at all coverages. At saturation a c(2 x 2) ordered layer of molecular iodine develops on top of a (2 x 2) ordered structure of atomic iodine binding to asymmetric Ge-dimers. Annealing destroys the molecular character and etches the surface by Ge dimer bond breaking and attachment of additional iodine to these Ge atoms to form GeI2, which desorbs from the surface.

  • 280. Ha, Dang Trinh
    et al.
    Wang, Y.
    Alcami, M.
    Itaelae, E.
    Kooser, K.
    Urpeainen, S.
    Huels, Michael A.
    KTH, School of Engineering Sciences (SCI), Physics, Atomic and Molecular Physics.
    Kukk, E.
    Martin, F.
    Fragmentation Dynamics of Doubly Charged Methionine Phase2014In: Journal of Physical Chemistry A, ISSN 1089-5639, E-ISSN 1520-5215, Vol. 118, no 8, p. 1374-1383Article in journal (Refereed)
    Abstract [en]

    The dependence of the fragmentation of doubly charged gas-phase methionine (C5H11NO2S) on the electronic-state character of the parent ion is studied experimentally by energy-resolved electron ion-ion coincidence spectroscopy. The parent dication electronic states are populated by Auger transitions following site-specific sulfur 2p core ionization. Two fragmentation channels are observed to be strongly dependent on the electronic states with vacancies in weakly bound molecular orbitals. All-electron calculations are applied to assign doubly charged final states of sulfur 2p core ionized methionine. In addition, the Car-Parrinello method is applied to model fragmentation dynamics of doubly charged methionine molecules with various initial temperatures to understand the typical characteristics of the molecular dissociation and partly to support the interpretation of experimental data.

  • 281. Haeffner, F.
    et al.
    Brinck, Tore
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry.
    How does methyllithium invert? A density functional study2001In: Organometallics, ISSN 0276-7333, E-ISSN 1520-6041, Vol. 20, no 24, p. 5134-5138Article in journal (Refereed)
    Abstract [en]

    Quantum chemical studies (B3LYP) of the inversion of methyllithium in both tetrameric and dimeric aggregates have been carried out. Results show that inversion occurs either via dissociation of the tetramer into the dimers, passage of a four-membered-ring transition state, and association of the dimers to form the inverted tetramer, or via a nonconcerted route involving an eight-membered-ring transition state. The activation energies of these two mechanisms are similar. However, the dissociative mechanism is ruled out by NMR experiments.

  • 282. Hagström, Magnus
    et al.
    Engvall, Klas
    Pettersson, Jan B. C.
    Desorption Kinetics at Atmospheric Pressure: Alkali Metal Ion Emission from Hot Platinum Surfaces2000In: Journal of Physical Chemistry B, Vol. 104, no 18, p. 4457-4462Article in journal (Refereed)
  • 283. Hahlin, Maria
    et al.
    Johansson, Erik M. J.
    Plogmaker, Stefan
    Odelius, Michael
    Hagberg, Daniel
    KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Sun, Licheng
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Siegbahn, Hans
    Rensmo, Hakan
    Electronic and molecular structures of organic dye/TiO2 interfaces for solar cell applications: a core level photoelectron spectroscopy study2010In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 12, no 7, p. 1507-1517Article in journal (Refereed)
    Abstract [en]

    The electronic and molecular properties of three organic dye molecules with the general structure donor-linker-anchor have been investigated using core level photoelectron spectroscopy (PES). The molecules contain a diphenylaniline donor unit, a thiophene linker unit, and cyanoacrylic acid or rhodanine-3-acetic acid anchor units. They have been investigated both in the form of a multilayer and adsorbed onto nanoporous TiO2 and the experimental results were also compared with DFT calculations. The changes at the dye-sensitized TiO2 surface due to the modification of either the donor unit or the anchor unit was investigated and the results showed important differences in coverage as well as in electronic and molecular surface properties. By measuring the core level binding energies, the sub-molecular properties were characterized and the result showed that the adsorption to the TiO2 influences the energy levels of the sub-molecular units differently.

  • 284.
    Hajian, Alireza
    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. KTH.
    Lindström, Stefan B.
    Linköping University.
    Pettersson, Torbjörn
    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. KTH.
    Hamedi, Mahiar M.
    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. KTH.
    Wågberg, Lars
    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. KTH.
    Understanding the Dispersive Action of Nanocellulose for Carbon Nanomaterials2017In: Nano letters (Print), ISSN 1530-6984, E-ISSN 1530-6992, Vol. 17, no 3, p. 1439-1447Article in journal (Refereed)
    Abstract [en]

    This work aims at understanding the excellent ability of nanocelluloses to disperse carbon nanomaterials (CNs) in aqueous media to form long-term stable colloidal dispersions without the need for chemical functionalization of the CNs or the use of surfactant. These dispersions are useful for composites with high CN content when seeking water-based, efficient, and green pathways for their preparation. To establish a comprehensive understanding of such dispersion mechanism, colloidal characterization of the dispersions has been combined with surface adhesion measurements using colloidal probe atomic force microscopy (AFM) in aqueous media. AFM results based on model surfaces of graphene and nanocellulose further suggest that there is an association between the nanocellulose and the CN. This association is caused by fluctuations of the counterions on the surface of the nanocellulose inducing dipoles in the sp2carbon lattice surface of the CNs. Furthermore, the charges on the nanocellulose will induce an electrostatic stabilization of the nanocellulose–CN complexes that prevents aggregation. On the basis of this understanding, nanocelluloses with high surface charge density were used to disperse and stabilize carbon nanotubes (CNTs) and reduced graphene oxide particles in water, so that further increases in the dispersion limit of CNTs could be obtained. The dispersion limit reached the value of 75 wt % CNTs and resulted in high electrical conductivity (515 S/cm) and high modulus (14 GPa) of the CNT composite nanopapers.

  • 285.
    Hallberg, Fredrik
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry.
    Molecular Interactions Studied by Electrophoretic and Diffusion NMR2010Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Even though electrophoretic NMR (eNMR) experiments may provide unique chemical information and have been performed for three decades, the technique is still rarely applied, mainly because several experimental sources of artifacts have to be controlled to achieve accurate results. In this thesis, new experimental setups and protocols for accurate and precise eNMR experiments are presented. These include a novel eNMR sample cell, a radiofrequency filter and methods to suppress bulk flow effects. These developments improved the signal-to-noise ratio by roughly an order of magnitude compared to the U-tube setup previously used for eNMR. Convection-compensated pulse sequences in combination with a phase correction method were found to efficiently suppress bulk flow effects in the experiments and greatly increase experimental accuracy.

    These experimental setups and protocols were applied to probe association of ions and molecules in solution. It is particularly illustrated that the combination of diffusion and eNMR has great potential to provide quantitative results on ionic and molecular association in a variety of systems.

    The extent to which ionic surfactants associate with uncharged cyclodextrin probed by eNMR yielded very similar results to those obtained by diffusion NMR experiments. Complexation of a large set of small mono- and polyvalent metal cations to poly(ethylene oxide) was quantified by estimating the effective charge of the polymer through combined diffusion and eNMR information. Significant association was found for cations that have a surface charge density below a critical value.

    Ion pairing between tetramethylammonium cations and a series of anions in several solvents was also probed by diffusion NMR and eNMR experiments. For the monovalent anions in ethanol and ethanol-water mixture a dependence on ionic size was demonstrated. In water, dimethylsulfoxide, and methanol no such trend and very little pairing was observed. In acetonitrile, a different pattern was seen that did not correlate well with any single ionic parameter.

    An experimental cell and procedures for electrokinetic studies of solvated proton-conducting polymer materials is also presented. Electro-osmotic flow and diffusion were studied for each molecular component in water-methanol mixtures that swell Nafion membranes.

  • 286.
    Halldin Stenlid, Joakim
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Computational Studies of Chemical Interactions: Molecules, Surfaces and Copper Corrosion2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The chemical bond – a corner stone in science and a prerequisite for life – is the focus of this thesis. Fundamental and applied aspects of chemical bonding are covered including the development of new computational methods for the characterization and rationalization of chemical interactions. The thesis also covers the study of corrosion of copper-based materials. The latter is motivated by the proposed use of copper as encapsulating material for spent nuclear fuel in Sweden.

    In close collaboration with experimental groups, state-of-the-art computational methods were employed for the study of chemistry at the atomic scale. First, oxidation of nanoparticulate copper was examined in anoxic aqueous media in order to better understand the copper-water thermodynamics in relation to the corrosion of copper material under oxygen free conditions. With a similar ambition, the water-cuprite interface was investigated with regards to its chemical composition and reactivity. This was compared to the behavior of methanol and hydrogen sulfide at the cuprite surface.

    An overall ambition during the development of computational methods for the analysis of chemical bonding was to bridge the gap between molecular and materials chemistry. Theory and results are thus presented and applied in both a molecular and a solid-state framework. A new property, the local electron attachment energy, for the characterization of a compound’s local electrophilicity was introduced. Together with the surface electrostatic potential, the new property predicts and rationalizes regioselectivity and trends of molecular reactions, and interactions on metal and oxide nanoparticles and extended surfaces.

    Detailed atomistic understanding of chemical processes is a prerequisite for the efficient development of chemistry. We therefore envisage that the results of this thesis will find widespread use in areas such as heterogeneous catalysis, drug discovery, and nanotechnology.

  • 287.
    Halldin Stenlid, Joakim
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Brinck, Tore
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Extending the σ-Hole Concept to Metals: An Electrostatic Interpretation of the Nanostructural Effects in Gold and Platinum Catalysis2017In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126Article in journal (Refereed)
    Abstract [en]

    Crystalline surfaces of gold are chemically inert, whereas nanoparticles of gold are excellent catalysts for many reactions. The catalytic properties of nanostructured gold have been connected to increased binding affinities of reactant molecules to low-coordinated Au atoms. Here we show that the high reactivity at these sites is a consequence of the formation of σ-holes, i.e. maxima in the surface electrostatic potential (Vs,max) due to the overlap of mainly the valence s-orbitals when forming the bonding σ-orbitals. The σ-holes are binding sites for Lewis bases, and binding energies correlate with magnitudes of the Vs,max. For symmetrical Au clusters, of varying size, the most positive Vs,max are found at corners, edges, and surfaces (facets) and decreasing in that order. This is in agreement with the experimentally and theoretically observed dependence of catalytic activity on local structure. The density of σ-holes can explain the increasing catalytic activity with decreasing particle size also for other transition metal catalysts, such as platinum.

  • 288.
    Halldin Stenlid, Joakim
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Johansson, Adam Johaness
    Brinck, Tore
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    σ-Holes on Transition Metal Nanoclusters and Their Influence on the Local Lewis Acidity2017In: Crystals, ISSN 2073-4352, Vol. 7, article id 222Article in journal (Refereed)
    Abstract [en]

    Understanding the molecular interaction behavior of transition metal nanoclusters lies at the heart of their efficient use in, e.g., heterogeneous catalysis, medical therapy and solar energy harvesting. For this purpose, we have evaluated the applicability of the surface electrostatic potential [VS(r)] and the local surface electron attachment energy [ES(r)] properties for characterizing the local Lewis acidity of a series of low-energy TM13 transition metal nanoclusters (TM = Au, Cu, Ru, Rh, Pd, Ir, Pt, Co), including also Pt7Cu6. The clusters have been studied using hybrid Kohn–Sham density functional theory (DFT) calculations. The VS(r) and ES(r), evaluated at 0.001 a.u. isodensity contours, are used to analyze the interactions with H2O. We find that the maxima of VS(r), σ-holes, are either localized or diffuse. This is rationalized in terms of the nanocluster geometry and occupation of the clusters’s, p and d valence orbitals. Our findings motivate a new scheme for characterizing σ-holes as σs (diffuse), σp (localized) or σd (localized) depending on their electronic origin. The positions of the maxima in VS(r) (and minima in ES(r)) are found to coincide with O-down adsorption sites of H2O, whereas minima in VS(r) leads to H-down adsorption. Linear relationships between VS,max (and ES,min) and H2O interaction energies are further discussed.

  • 289.
    Halldin Stenlid, Joakim
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Johansson, Adam Johannes
    The Local Electron Attachment Energy and the Electrostatic Potential as Descriptors of Surface- Adsorbate InteractionsManuscript (preprint) (Other academic)
  • 290.
    Halldin Stenlid, Joakim
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Johansson, Adam Johannes
    Brinck, Tore
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Local Lewis Acidity of (TiO2)n n=7-10 Nanoparticles Characterized by DFT-Based DescriptorsManuscript (preprint) (Other academic)
  • 291.
    Halldin Stenlid, Joakim
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry. Stockholm Univ, AlbaNova Univ Ctr, Dept Phys, SE-10691 Stockholm, Sweden..
    Johansson, Adam Johannes
    Swedish Nucl Fuel & Waste Management Co SKB, Evenemangsgatan 13,Box 3091, SE-16903 Solna, Sweden..
    Brinck, Tore
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    The local electron attachment energy and the electrostatic potential as descriptors of surface-adsorbate interactions2019In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 21, no 31, p. 17001-17009Article in journal (Refereed)
    Abstract [en]

    Two local reactivity descriptors computed by Kohn-Sham density functional theory (DFT) are used to predict and rationalize interactions of nucleophilic molecules (exemplified by CO and H2O) with transition metal (TM) and oxide surfaces. The descriptors are the electrostatic potential, V-S(r), and the local electron attachment energy, E-S(r), evaluated on surfaces defined by the 0.001 e Bohr(-3) isodensity contour. These descriptors have previously shown excellent abilities to predict regioselectivity and rank molecular as well as nanoparticle reactivities and interaction affinities. In this study, we generalize the descriptors to fit into the framework of periodic DFT computations. We also demonstrate their capabilities to predict local surface propensity for interaction with Lewis bases. It is shown that E-S(r) and V-S(r) can rationalize the interaction behavior of TM oxides and of fcc TM surfaces, including low-index, stepped and kinked surfaces spanning a wide range of interaction sites with varied coordination environments. Broad future applicability in surface science is envisaged for the descriptors, including heterogeneous catalysis and electrochemistry.

  • 292.
    Halldin Stenlid, Joakim
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Johansson, Adam Johannes
    Brinck, Tore
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    σ-Holes and σ-Lumps Direct the Lewis Basic and Acidic Interactions of Noble Metal Nanoparticles: Introducing Regium BondsManuscript (preprint) (Other academic)
  • 293. Hallstedt, Bengt
    et al.
    Dupin, Nathalie
    Hillert, Mats
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Höglund, Lars
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Physical Metallurgy.
    Lukas, Hans Leo
    Schuster, Julius C.
    Solak, Nuri
    Thermodynamic models for crystalline phases. Composition dependent models for volume, bulk modulus and thermal expansion2007In: Calphad, ISSN 0364-5916, E-ISSN 1873-2984, Vol. 31, no 1, p. 28-37Article in journal (Refereed)
    Abstract [en]

    The thermodynamic modelling of solid (crystalline) phases forms a central topic within the Calphad approach and a variety of aspects have been discussed at previous Ringberg workshops. At the present Ringberg workshop, modelling of volume and its temperature, pressure and composition dependence formed a major part of the discussions. In addition, modelling of the heat capacity above the (equilibrium) melting temperature, sublattice modelling of complex phases, modelling of ordering and interstitial solutions in the bcc lattice and the effect of magnetism were addressed.

  • 294.
    Halthur, Tobias
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Multilayer Structures for Biomaterial Applications: Biomacromolecule-based Coatings2005Doctoral thesis, comprehensive summary (Other scientific)
    Abstract [en]

    The cellular response to a biomaterial, such as a dental implant, is mainly governed by the surface properties, and can thus be altered by the introduction of a surface coating. In this thesis the buildup of a biomacromolecule-based coating formed by layerby-layer (LbL) deposition of the charged polypeptides poly(L-lysine) (PLL) and poly(L-glutamic acid) (PGA) has been studied. In an attempt to make these coatings bioactive and useful for bone-anchored implants, an amelogenin protein mixture (EMD), has been immobilized in these thin polyelectrolyte multilayer (PEM) films. Multilayers were also built by LbL deposition of the natural biomacromolecules collagen (Col) and hyaluronic acid (HA). Multilayer films of these two extra-cellular biomacromolecules should be of interest for use as a scaffold for tissue engineering.

    The buildup of the multilayer films has been followed in situ, using ellipsometry, quartz crystal microbalance with dissipation (QCM-D), and dual polarization interferometry (DPI). The studied PLL/PGA multilayers were found to be highly hydrated, and to exhibit a two-regime buildup behavior, with an initial “slow-growing” regime, and a second “fast-growing” regime with a linear growth in film thickness and more than linear growth in mass. A net diffusion of polypeptides into the film during the buildup led to an increase in density of the films for each layer adsorbed. A change in density was also observed in the Col/HA film, where HA penetrated and diffused into the porous fibrous Col network.

    The formed PLL/PGA films were further found to be rather stable during drying, and post-buildup changes in temperature and pH, not losing any mass as long as the temperature was not raised too rapidly. The film thickness responded to changes in the ambient media and collapsed reversibly when dried. A swelling/de-swelling behavior of the film was also observed for changes in the temperature and pH.

    The EMD protein adsorbed to silica surfaces as nanospheres, and could by itself form multilayers. The adsorption of EMD onto PLL/PGA multilayer films increased at lower pH (5.0), and EMD could be immobilized in several layers by alternate deposition of EMD and PGA.

  • 295.
    Halthur, Tobias
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry (closed 20081231).
    Björklund, Anna
    YKI, Institute for Surface Chemistry.
    Elofsson, Ulla
    YKI, Institute for Surface Chemistry.
    Self-assembly/aggregation behavior and adsorption of enamel matrix derivate protein to silica surfaces2006In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 22, no 5, p. 2227-2234Article in journal (Refereed)
    Abstract [en]

    Adsorption of the amelogein protein mixture enamel matrix derivate (EMD) to silica surfaces has been studied by in situ ellipsometry and quartz crystal microbalance with dissipation (QCM-D). The protein was found to adsorb as nanospheres in mono- or multilayers, depending on the concentration of "free" nanospheres available in solution. The concentration of free nanospheres is determined by the competitive processes of adsorption and rapid aggregation into microscopic particles, measured by dynamic light scattering (DLS). Multilayers could also be formed by sequential injections of fresh EMD solution. At higher temperature, an up to 6 times thicker gel-like film was formed on the substrate surface, and decreasing the pH lead to disruption of the multi layer/aggregate formation and a decreased amount adsorbed.

  • 296.
    Halthur, Tobias
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Claesson, Per M.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Elofsson, Ulla
    Immobilization of Enamel Matrix Derivate Protein onto Polypeptide Multilayers: Comparative in Situ Measurements using Ellipsometry, Quartz Crystal Microbalance with Dissipation, and Dual Polarization Interferometry2006In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 22, no 26, p. 11065-11071Article in journal (Refereed)
    Abstract [en]

    The buildup of biodegradable poly(L-glutamic acid) (PGA) and poly(L-lysine) (PLL) multilayers on silica and titanium surfaces and the immobilization of enamel matrix derivate (EMD) protein was followed by utilizing in situ ellipsometry, quartz crystal microbalance with dissipation, and dual-polarization interferometry (DPI). The use of the relatively new DPI technique validated earlier published ellipsometry measurements of the PLL-PGA polypeptide films. The hydrophobic aggregating EMD protein was successfully immobilized both on top of and within the multilayer structures at pH 5.0. DPI measurements further indicated that the immobilization of EMD is influenced by the flow pattern during adsorption. The formed polypeptide-EMD multilayer films are of interest since it is known that EMD is able to trigger cell response and induce biomineralization. The multilayer films thus have potential to be useful as bioactive and biodegradable coatings for future dental implants.

  • 297.
    Halthur, Tobias
    et al.
    KTH, Superseded Departments, Chemistry.
    Claesson, Per M.
    KTH, Superseded Departments, Chemistry.
    Elofsson, Ulla
    Stability of Polypeptide Multilayers As Studied by in Situ Ellipsometry: Effects of Drying and Post-Buildup Changes in Temperature and pH2004In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 126, no 51, p. 17009-17015Article in journal (Refereed)
    Abstract [en]

    Polyelectrolyte multilayers (PEM) of poly(L-glutamic acid) (PGA) and poly(L-lysine) (PLL) with an initial layer of polyethyleneimine (PEI) were built on silica and titanium surfaces using the layer-by-layer (LbL) technique. The stability of the film during drying/rewetting, temperature cycles, and pH shifts was studied in situ by means of ellipsometry. The film thickness was found to decrease significantly (approximately 70%) upon drying, but the original film thickness was regained upon rewetting, and the buildup could be continued. The thickness in the dry state was found to be extremely sensitive to ambient humidity, needing several hours to equilibrate. Changes in temperature and pH were also found to influence the multilayer thickness, leading to swelling and deswelling of as much as 8% and 10-20% respectively. The film does not necessarily regain its original thickness as the pH is shifted back, but instead shows clear signs of hysteresis.

  • 298.
    Halthur, Tobias
    et al.
    KTH, Superseded Departments, Chemistry.
    Elofsson, Ulla
    YKI, Institute for Surface Chemistry.
    Multilayers of Charged Polypeptides As Studied by in Situ Ellipsometry and Quartz Crystal Microbalance with Dissipation2004In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 20, no 5, p. 1739-1745Article in journal (Refereed)
    Abstract [en]

    The buildup of poly(L-glutamic acid) (PGA) and poly(L-lysine) (PLL) multilayers on silica and titanium surfaces, with and without an initial layer of polyethyleneimine (PEI), was investigated and characterized by means of in situ ellipsometry and quartz crystal microbalance with dissipation. A two-regime buildup was found in all systems, where the length of the first slow-growing regime is dependent on the structure of the initial layers. In the second fast-growing regime, the film thickness grows linearly while the mass increases more than linearly (close to exponentially) with the number of deposited layers. The film refractive indices as well as the water contents indicate that the film density changes as the multilayer film builds up. The change in film density was proposed to be due to polypeptides diffusing into the multilayer film as they attach. Furthermore, the use of PEI as the initial layer was found to induce a difference in the thickness increments for PGA and PLL.

  • 299.
    Hamedi, Mahiar
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Wågberg, Lars
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Nyström, Gustav
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Marais, Andrew
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Karabulut, Erdem
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Cui, Yi
    Stanford Univ, Stanford, CA 94305 USA..
    Soft, compressible and fully Interdigitated 3D energy storage devices built by layer-by-layer assembly inside aerogels2015In: Abstract of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 249Article in journal (Other academic)
  • 300. Hamzavi, M.
    et al.
    Rajabi, A. A.
    Thylwe, Karl -Erik
    KTH, School of Engineering Sciences (SCI), Mechanics.
    The rotation-vibration spectrum of diatomic molecules with the tietz-hua rotating oscillator2012In: International Journal of Quantum Chemistry, ISSN 0020-7608, E-ISSN 1097-461X, Vol. 112, no 15, p. 2701-2705Article in journal (Refereed)
    Abstract [en]

    The Tietz-Hua (TH) potential is one of the very best analytical model potentials for the vibrational energy of diatomic molecules. By using the Nikiforov-Uvarov method, we have obtained the exact analytical s-wave solutions of the radial Schrodinger equation for the TH potential. The energy eigenvalues and the corresponding eigenfunctions are calculated in closed forms. Some numerical results for diatomic molecules are also presented.

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