| 1. |
- Bergman, Nina, et al.
(författare)
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Approaches for the analysis of low molecular weight compounds with laser desorption/ionization techniques and mass spectrometry
- 2014
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Ingår i: Analytical and Bioanalytical Chemistry. - : Springer Science and Business Media LLC. - 1618-2642 .- 1618-2650. ; 406:1, s. 49-61
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Forskningsöversikt (refereegranskat)abstract
- This review summarizes various approaches for the analysis of low molecular weight (LMW) compounds by different laser desorption/ionization mass spectrometry techniques (LDI-MS). It is common to use an agent to assist the ionization, and small molecules are normally difficult to analyze by, e.g., matrix assisted laser desorption/ionization mass spectrometry (MALDI-MS) using the common matrices available today, because the latter are generally small organic compounds themselves. This often results in severe suppression of analyte peaks, or interference of the matrix and analyte signals in the low mass region. However, intrinsic properties of several LDI techniques such as high sensitivity, low sample consumption, high tolerance towards salts and solid particles, and rapid analysis have stimulated scientists to develop methods to circumvent matrix-related issues in the analysis of LMW molecules. Recent developments within this field as well as historical considerations and future prospects are presented in this review.
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| 2. |
- Bergman, Nina, et al.
(författare)
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Quantitative determination of the Ru(bpy)(3)(2+) cation in photochemical reactions by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry
- 2014
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Ingår i: Analytical Methods. - : Royal Society of Chemistry (RSC). - 1759-9660 .- 1759-9679. ; 6:21, s. 8513-8518
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Tidskriftsartikel (refereegranskat)abstract
- The coordination compound of Ru(II) with three 2,2'-bipyridine ligands possesses a potent photosensitization capacity for electron- and energy-transfer processes. In combination with salts of peroxydisulfate acid as sacrificial electron acceptors, Ru(bpy)(3)(2+) is widely used for photocatalytic oxidative transformations in organic synthesis and water splitting. The drawback of this system is that bipyridine degrades under the resulting strongly oxidative conditions, the concentration of Ru(bpy)(3)(2+) diminishes, and the photocatalytic reaction eventually stops. A commonly employed assay for the determination of Ru(bpy)(3)(2+), UV-Vis spectroscopy, has low selectivity and does not distinguish between the intact complex and its decayed forms. Here, we report a matrix assisted laser desorption/ionisation mass spectrometric method for the quantitative analysis of Ru(bpy)(3)(2+) in photochemical reaction mixtures. The developed method was successfully used for the determination of intact Ru(bpy)(3)(2+) during the course of the water photooxidation reaction. The significant difference between the results of MALDI MS and UV-Vis analyses was observed.
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| 3. |
- Ellis, Hanna, 1985-, et al.
(författare)
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Laser desorption/ionization mass spectrometry of dye-sensitized solar cells : identification of the dye-electrolyte interaction
- 2015
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Ingår i: Journal of Mass Spectrometry. - : Wiley. - 1076-5174 .- 1096-9888. ; 50:5, s. 734-739
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Tidskriftsartikel (refereegranskat)abstract
- Dye-sensitized solar cells (DSCs) have great potential to provide sustainable electricity from sunlight. The photoanode in DSCs consists of a dye-sensitized metal oxide film deposited on a conductive substrate. This configuration makes the photoanode a perfect sample for laser desorption/ionization mass spectrometry (LDI-MS). We applied LDI-MS for the study of molecular interactions between a dye and electrolyte on the surface of a TiO2 photoanode. We found that a dye containing polyoxyethylene groups forms complexes with alkali metal cations from the electrolyte, while a dye substituted with alkoxy groups does not. Guanidinium ion forms adducts with neither of the two dyes.
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| 4. |
- Risch, Marcel, et al.
(författare)
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Atomic structure of cobalt-oxide nanoparticles activein light-driven catalysis of water oxidation
- 2012
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Ingår i: International journal of hydrogen energy. - : Elsevier BV. - 0360-3199 .- 1879-3487. ; 37:10, s. 8878-8888
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Tidskriftsartikel (refereegranskat)abstract
- The atomic structure of water-oxidizing nanoparticles (10-60 nm) formed from cobalt(II)salts and methylenediphosphonate (M2P) is investigated. These amorphous nanoparticles are of high interest for production of solar fuels. They facilitate water oxidation in a directly light-driven process using [Ru(bpy)3]2+ (bpy = 2,2’-bipyridine) as a photosensitizer and persulfate (S2O82-) as an electron acceptor. By X-ray absorption spectroscopy (XAS) at the cobalt K-edge, cobalt L-edge and oxygen K-edge, we investigate the light-driven transition from the CoII/M2P precursor to the active catalyst, which is a layered cobalt(III) oxide with structural similarities to water-oxidizing electrocatalysts. The M2P ligand likely binds at the periphery of the nanoparticles, preventing their further agglomeration during the catalytic reaction. This system opens a possibility to link the catalytically active nanoparticles via a covalent bridge to a photosensitizer and build an artificial photosynthetic system for direct utilization of solar energy for fuel production without production of electricity as an intermediate step.
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| 5. |
- Semenaka, Valentyna V., et al.
(författare)
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Direct synthesis of an heterometallic {(Mn3Cr4III)-Cr-II} wheel by decomposition of Reineckes salt
- 2010
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Ingår i: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9226 .- 1477-9234. ; 39:9, s. 2344-2349
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Tidskriftsartikel (refereegranskat)abstract
- A new heterometallic Mn/Cr molecular wheel complex has been synthesized using zerovalent manganese, Reineckes salt, ammonium thiocyanate and triethanolamine (H(3)tea) as starting materials. The compound [Mn3Cr4(NCS)(6)(Htea)(6)] (1) has been characterized in terms of its electrochemical, IR and EPR spectroscopic as well as its magnetic properties. The magnetic susceptibility and magnetization data were treated simultaneously during the optimization routine and resulted in J(Mn-Cr) = + 0.43 cm(-1), J(Cr-Cr) = -4.75 cm(-1), J(Mn-Mn) = +1.78 cm(-1), g(eff) = 1.878 with the ground state S = 15/2.
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| 6. |
- Shevchenko, Denys, et al.
(författare)
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Photochemical water oxidation with visible light using a cobalt containing catalyst
- 2011
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Ingår i: Energy and Environmental Science. - : RSC Publishing. - 1754-5692 .- 1754-5706. ; 4:4, s. 1284-1287
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Tidskriftsartikel (refereegranskat)abstract
- Artificial photosynthesis aims at using solar light energy to oxidatively split water to oxygen, protons and electrons and store the energy in a chemical fuel. Here we present a cobalt phosphonate material that can split water catalytically, driven by visible light in aqueous solutions of pH 7.
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| 7. |
- Shevchenko, Denys, et al.
(författare)
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Synthesis, crystal structure, mass spectrometry, electrochemistry and magnetism of a Mn-III-substituted trilacunary Keggin tungstosilicate
- 2013
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Ingår i: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9226 .- 1477-9234. ; 42:14, s. 5130-5139
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Tidskriftsartikel (refereegranskat)abstract
- A rare example of a "monomeric" triple transition-metal substituted Keggin anion has been synthesized and characterized by various methods including X-ray crystallography, ESI and MALDI mass spectrometry, electrochemistry, EPR, and SQUID.
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| 8. |
- Shevchenko, Denys V., et al.
(författare)
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Direct template synthesis of a heterometallic Co-III/Zn-II complex : The advantage of using a metal powder as a starting material
- 2008
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Ingår i: Inorganic Chemistry Communications. - : Elsevier BV. - 1387-7003 .- 1879-0259. ; 11:10, s. 1209-1211
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Tidskriftsartikel (refereegranskat)abstract
- The heterometallic complex [Co(L-1)Cl-2][ZnCl3(DMF)] (L-1 = 4,6,6-trimethyl-1,9-diamino-3,7-diazanon-3-ene) has been obtained by direct template synthesis from cobalt powder, zinc oxide, zinc chloride, ethylenediamine dihydrochloride and acetone in dimethylformamide and characterized by X-ray crystallographic analysis. The mechanism of the complex formation is suggested.
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| 9. |
- Shevchenko, Denys, et al.
(författare)
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Water oxidation by manganese oxides formed from tetranuclear precursor complexes : the influence of phosphate on structure and activity
- 2014
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Ingår i: Physical Chemistry, Chemical Physics - PCCP. - : Royal Society of Chemistry (RSC). - 1463-9076 .- 1463-9084. ; 16:24, s. 11965-11975
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Tidskriftsartikel (refereegranskat)abstract
- Two types of manganese oxides have been prepared by hydrolysis of tetranuclear Mn(III) complexes in the presence or absence of phosphate ions. The oxides have been characterized structurally using X-ray absorption spectroscopy and functionally by O-2 evolution measurements. The structures of the oxides prepared in the absence of phosphate are dominated by di-mu-oxo bridged manganese ions that form layers with limited long-range order, consisting of edge-sharing MnO6 octahedra. The average manganese oxidation state is +3.5. The structure of these oxides is closely related to other manganese oxides reported as water oxidation catalysts. They show high oxygen evolution activity in a light-driven system containing [Ru(bpy)(3)](2+) and S2O82- at pH 7. In contrast, the oxides formed by hydrolysis in the presence of phosphate ions contain almost no di-mu-oxo bridged manganese ions. Instead the phosphate groups are acting as bridges between the manganese ions. The average oxidation state of manganese ions is +3. This type of oxide has much lower water oxidation activity in the light-driven system. Correlations between different structural motifs and the function as a water oxidation catalyst are discussed and the lower activity in the phosphate containing oxide is linked to the absence of protonable di-mu-oxo bridges.
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| 10. |
- Zhang, Jinbao, et al.
(författare)
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Matrix-Assisted Laser Desorption/Ionization Mass Spectrometric Analysis of Poly(3,4-ethylenedioxythiophene) in Solid-State Dye-Sensitized Solar Cells : Comparison of In Situ Photoelectrochemical Polymerization in Aqueous Micellar and Organic Media
- 2015
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Ingår i: Analytical Chemistry. - : American Chemical Society (ACS). - 0003-2700 .- 1520-6882. ; 87:7, s. 3942-3948
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Tidskriftsartikel (refereegranskat)abstract
- Solid-state dye-sensitized solar cells (sDSCs) are devoid of such issues as electrolyte evaporation or leakage and electrode corrosion, which are typical for traditional liquid electrolyte-based DSCs. Poly(3,4-ethylenedioxythiophene) (PEDOT) is one of the most popular and efficient p-type conducting polymers that are used in sDSCs as a solid-state hole-transporting material. The most convenient way to deposit this insoluble polymer into the dye-sensitized mesoporous working electrode is in situ photoelectrochemical polymerization. Apparently, the structure and the physicochemical properties of the generated conducting polymer, which determine the photovoltaic performance of the corresponding solar cell, can be significantly affected by the preparation conditions. Therefore, a simple and fast analytical method that can reveal information on polymer chain length, possible chemical modifications, and impurities is strongly required for the rapid development of efficient solar energy-converting devices. In this contribution, we applied matrix-assisted laser desorption/ionization mass spectrometry (MALDI MS) for the analysis of PEDOT directly on sDSCs. It was found that the PEDOT generated in aqueous micellar medium possesses relatively shorter polymeric chains than the PEDOT deposited from an organic medium. Furthermore, the micellar electrolyte promotes a transformation of one of the thiophene terminal units to thiophenone. The introduction of a carbonyl group into the PEDOT molecule impedes the growth of the polymer chain and reduces the conductivity of the final polymer film. Both the simplicity of sample preparation (only application of the organic matrix onto the solar cell is needed) and the rapidity of analysis hold the promise of making MALDI MS an essential tool for the physicochemical characterization of conducting polymer-based sDSCs.
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