| 1. |
- Aas, Wenche
(författare)
-
Constitution, dynamics and structure of binary and ternary actinide complexes
- 1999
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Stoichiometry, ligand exchange reactions, coordinationgeometry and stability of complexes of type UO2LpFq(H2O)3-n(p= 1–2,q= 1-3), where L is one of the bidentate ligandspicolinate, oxalate, carbonate or acetate have beeninvestigated using single crystal X-ray diffraction, an arrayof19F-,13C-,17O- and1H-NMR techniques and potentiometric titration usingboth F-and H+selective electrodes. The experiments wereperformed in a 1.00 M NaClO4medium. The equilibrium constants were determinedat 25°C while most of the kinetic experiments were done at- 5°C. The equilibrium constants for the stepwise additionof F-to UO2L and UO2L2indicates that the prior coordination of L toU(VI) has a fairly small effect on the subsequent bonding offluoride, except for a statistical effect determined by thenumber of available coordination sites. This indicates thatternary complexes might be important for the speciation andtransport of hexavalent actinides in ground and surface watersystems. A single crystal structure of UO2(picolinate)F32-has been determined showing the same pentagonalbipyramidal symmetry as in aqueous solution studied by NMR. Theexchangeable donor atoms are situated in a plane perpendicularto the linear uranyl group. The complexes show a variety ofdifferent exchange reactions depending on the ligand used. Ithas been possible to quantify external fluoride and the otherligands exchange reactions as well asintra-molecular reactions. This type of detailedinformation has not been observed in aqueous solution before.Water takes a critical part in the exchange mechanism, and whenit is eliminated from the inner coordination sphere a muchslower kinetics can be observed.19F-NMR has showed to be a powerful technique tostudy these reactions, both because of the sensitivity of thisNMR nucleus and also the possibility to observe reactions wherefluoride is not directly involved in the mechanism. TernaryTh(edta)F1-2and (UO2)2(edta)2F1-4have been investigated using1H and19F-NMR. The fluoride complexation to Cm(III) wasstudied using time resolved fluorescence spectroscopy (TRLFS)and the stability constant for the CmF2+complex was determined at 25°C in 1.0 mNaCl.Keywords. Ternary complexes, actinides,dioxouranium(VI), curium(III), thorium(IV), ligand exchange,isomers, NMR, potentiometric titrations, aqueous solution,oxalate, picolinate, acetate, EDTA.
|
|
| 2. |
|
|
| 3. |
|
|
| 4. |
|
|
| 5. |
- Bring, Torun, 1960-
(författare)
-
Red Glass Coloration : a Colorimetric and Structural Study
- 2006
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Syftet med detta arbete har varit att försöka hitta alternativ till det kadmiumbase¬rade röda pigment som används idag. Detta har gjorts genom att delvis under¬söka kombinationer av grundämnen som i litteraturen finns omnämnda som röda glaspigment, delvis genom att försöka förbättra och underlätta produktionen av redan kända, men problematiska pigment. Det har konstaterats att det går att framställa ett rött glas när man smälter soda¬kalkglas med en kombination av molybden och selen, under reducerande beting¬elser. Rött glas med denna kombination har inte rapporterats tidigare. Pigmentet är känsligt för vilken glassammansättning man använder och flera vanliga glas¬komponenter måste undvikas. För att utvärdera färgen hos glasen användes UV/vis-spektroskopi och färgkoordinater i CIE-systemet. Både ESCA- och XANES-analyser visar att molybden finns i glaset som Mo6+joner. Färgen upp¬kommer troligtvis genom en interaktion mellan molybdenjonerna och selen i reducerad form. UV/Vis- och XANES spektra visar att selen finns i glaset i redu¬cerad form. Färgutvecklingen hos kopparrubinglas studerades med UV/vis-spektroskopi. Detta pigment behöver värmebehandlas för att färgen skall bildas. När låga vär¬mebehandlingstemperaturer och låga halter av de färgande komponenterna an¬vänds, är pigmentet stabilt under lång tid. Experimentella resultat från EXAFS- och TEM-analyser visar tydligt att färgkällan är metalliska kopparpartiklar i na¬nostorlek. Inverkan av olika reduktionsmedel på guld- och kopparrubinpigmenten har un¬dersökts. Det konstaterades att SnO är mer reducerande gentemot koppar än Sb2O3 i sodakalkglas. Kopparrubinglas kan framställas med bara endera av dessa reduktionsmedel, men SnO ger bättre resultat. Skift i absorbanstoppens läge och provets färg har observerats hos både guld- och kopparrubiner. Det största skiftet finns hos glas där en blåaktig ton erhållits. Skiftet beror troligtvis på att större partik¬lar bildats. Möjligheterna att kombinera röd färg med halvtransparenta alabasterglas har undersökts. Det konstaterades dock att alabastereffekten inte går att kombinera med pigment som kräver starkt reducerande miljöer. Både guld- och kopparrubiner är miljövänligare än det kadmiumbaserade pig¬mentet, och måste anses som möjliga alternativ. Mo/Se-pigmentet kan också vara ett alternativ.
|
|
| 6. |
- Eriksson, Margareta
(författare)
-
Ozone chemistry in aqueous solution : ozone decomposition and stabilisation
- 2005
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Ozone is used in many applications in the industry as an oxidising agent for example for bleaching and sterilisation. The decomposition of ozone in aqueous solutions is complex, and is affected by many properties such as, pH, temperature and substances present in the water. Additives can either accelerate the decomposition rate of ozone or have a stabilising effect of the ozone decay. By controlling the decomposition of ozone it is possible to increase the oxidative capacity of ozone. In this work the chemistry of acidic aqueous ozone is studied and ways to stabilise the decomposition of ozone in such solutions. The main work emphasizes the possibility to use surfactants in order to develop a new type of cleaning systems for the sterilisation of medical equipment.
|
|
| 7. |
- Gamstedt, Heléne, 1964-
(författare)
-
Ionic Liquid Electrolytes for Photoelectrochemical Solar Cells
- 2005
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Potential electrolytes for dye-sensitized photoelectrochemical solar cells have been synthesized and their applicability has been investigated. Different experimental techniques were used in order to characterize the synthesized electrolytes, such as elemental analysis, electrospray ionisation/mass spectrometry, cyclic voltammetry, dynamic viscosity measurements, as well as impedance, Raman and NMR spectroscopy. Some crystal structures were characterized by using single crystal X-ray diffraction. In order to verify the eligibility of the ionic compounds as electrolytes for photoelectrochemical solar cells, photocurrent density/photovoltage and incident photon-to-current conversion efficiency measurements were performed, using different kinds of light sources as solar simulators. In electron kinetic studies, the electron transport times in the solar cells were investigated by using intensitymodulated photocurrent and photovoltage spectroscopy. The accumulated charge present in the semiconductor was studied in photocurrent transient measurements. The ionic liquids were successfully used as solar cell electrolytes, especially those originating from the diethyl and dibutyl-alkylsulphonium iodides. The highest overall conversion efficiency of almost 4 % was achieved by a dye-sensitized, nanocrystalline solar cell using (Bu2MeS)I:I2 (100:1) as electrolyte (Air Mass 1.5 spectrum at 100 W m-2), quite compatible with the standard efficiencies provided by organic solvent-containing cells. Several solar cells with iodine-doped metal-iodidebased electrolytes reached stable efficiencies over 2 %. The (Bu2MeS)I:I2-containing cells showed better long-term stabilities than the organic solvent-based cells, and provided the fastest electron transports as well as the highest charge accumulation. Several polypyridyl-ruthenium complexes were tested as solar cell sensitizers. No general improvements could be observed according to the addition of amphiphilic co-adsorbents to the dyes or nanopartices of titanium dioxide to the electrolytes. For ionic liquid-containing solar cells, a saturation phenomena in the short-circuit current densities emerged at increased light intensities, probably due to inherent material transport limitation within the systems. Some iodoargentates and -cuprates were structurally characterized, consisting of monomeric or polymeric entities with anionic networks or layers. A system of metal iodide crownether complexes were employed and tested as electrolytes in photoelectrochemical solar cells, though with poorer results. Also, the crystal structure of a copper-iodide-(12-crown-4) complex has been characterized
|
|
| 8. |
- Lindsjö, Martin, 1975-
(författare)
-
On the nature of main-group polycations : an odyssey
- 2005
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Compounds containing main-group clusters, with focus on bismuth polycations, have been synthesized and characterized using X-ray diffraction and spectroscopic methods. Six new compounds have been isolated from synthesis in GaX3-arene media; Bi8[GaCl4]2, Bi8 [GaBr4]2, Sb8[GaCl4]2, Sb8[GaBr4]2, Te4[Ga2Cl7]2 and Te4[Ga2Br7]2. Sb2+ 8 is the first homopolyatomic antimony cation to be isolated. The cation forms a square antiprism, in correlation with Wade’s rules, and displays a significant difference in length between the inter-square and intra-square Sb–Sb distances. The geometries of the Sb2+ 8 cations in Sb8[GaCl4]2 and Sb8[GaBr4]2 are in excellent agreement; the average intra-square and intersquare Sb–Sb distances are 2.87 Å and 2.97 Å, respectively. A very strong Raman band attributed to Sb2+8 is found at 180 cm-1. The Bi2+8 (square antiprismatic) and Te2+4 (squareplanar) polycations are known from earlier compounds. The Bi–Bi distances in Bi8[GaCl4]2 (3.07–3.12 Å) are in general agreement with previous structures, while the Bi–Bi distances of Bi8[GaBr4]2 (2.92–3.18 Å) display a wider distrubution than previously observed. The Te–Te distances of the cations of Te4[Ga2Cl7]2 and Te4[Ga2Br7]2 are 2.66 and 2.67 Å, respectively. Quantum chemical calculations on bismuth polycations show that all species predicted byWade’s rules are local minima on a potential energy surface. The cation–anion interactions have been considered for salts containing bismuth polycations and it has been confirmed that such interactions have a major influence on the polycation stability. The new compound Bi16I4 has been isolated from molten Bil3. The structure consists of polymerized Bi16I4 molecules forming infinite ribbons and is very similar to the structure of the known metal-rich bismuth iodides, Bi14I4 and Bi18I4. DFT calculations predict all three compounds to be metallic conductors, while Bi4I4 is a semiconductor.
|
|
| 9. |
- Riihimäki, Eva-Stina, 1978-
(författare)
-
Structure and Dynamics of the Copper-binding Octapeptide Region in the Human Prion Protein
- 2005
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The copper-binding ability of the prion protein may be closely connected to its function. Identifying the exact function of the prion protein can clarify the underlying mechanism in prion diseases. In this work, the copper-binding octapeptide region in the human prion protein has been studied. The structural characteristics of the binding site are examined by quantum chemical structural optimization. The calculations aim at identifying a substitute for copper(II) to be used in NMR-spectroscopic studies of the copper-binding region. The dynamical and structural features of the peptide region are investigated in molecular dynamics simulations. Aspects of importance in the development of model systems in molecular dynamics simulation are addressed.
|
|
| 10. |
|
|
