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  • 1.
    Hellberg, Jonas
    et al.
    KTH, Superseded Departments, Chemistry.
    Dahlstedt, Emma
    KTH, Superseded Departments, Chemistry.
    Woldegiorgis, Andreas
    KTH, Superseded Departments, Chemistry.
    Umpolung of the 5-alkyl-2-dimethylamino-1,3-dithiolium-4-thiolate mesoion and its application in the synthesis of some new tetrathiafulvalenes2004In: European Journal of Organic Chemistry, ISSN 1434-193X, E-ISSN 1099-0690, no 7, p. 1455-1463Article in journal (Refereed)
    Abstract [en]

    The 5-alkyl-2-dimethylamino-1,3-dithiolium-4-thiolate mesoion could be umpoled with sulfuryl chloride to yield a dicationic electrophile 3 that reacted with various electron-rich aromatic substrates to yield arylthio-substituted 1,3-dithiolium salts 13-25. Two of these compounds have been transformed to the corresponding symmetrical tetrathiafulvalenes 43 and 44, and their cyclovoltammetric behaviour recorded.

  • 2.
    Woldegiorgis, Andreas
    KTH, Superseded Departments, Chemistry.
    Fabrication of new silica nano structures and development of new concepts for MALDI-TOF mass spectrometry2004Doctoral thesis, comprehensive summary (Other scientific)
    Abstract [en]

    A technique to alter the morphology of the inner surface of fused silica capillaries has been developed. The internal surface area is enlarged by means of nano-wires of silica, which are grown from the capillary walls. The growth is initiated by the decomposition of the etchant precursor 2-chloro-1,1,2–trifluoroethylmethyl ether at elevated temperature and pressure. It is suggested that the formation of the nano-wires is a process where hydrogen fluoride is continuously consumed and re-liberated. The amorphous bulk silica wall is dissolved, vaporized and finally condensed, yielding a directional re-formation of silica into nano-wire structures. The unidirectional growth of the nano-wires seems to follow the well-known vapor-liquid-solid (VLS) mechanism since characteristic attributes of the VLS mechanism can be observed in the modified capillaries, such as spherical particles terminating each nano-wire. An alternative procedure was developed based on non-isothermal etching which enabled nano-wire outgrowth in fused silica capillaries with internal diameters exceeding 5 µm. The etched and modified capillaries are expected to be suitable for fluidic applications where a higher surface-to-volume ratio is beneficial, such as open tubular liquid chromatography as well as solid-phase micro-reactors and catalysis including enzymatic reactions.

    The last part of the thesis describes new techniques developed for matrix-assisted laser desorption/ionization (MALDI) mass spectrometry. A set of novel matrices based on polymers/oligomers of benzodioxins and thiophenes has been introduced. Using this approach, which has been given the name Polymer-Assisted Laser Desorption/Ionization (PALDI), the low m/z-range of the mass spectrum, from 180 to 1.000 Da, could be used without the abundant chemical noise which normally disturbs such MALDI-MS spectra. Some of the PALDI matrices also showed excellent behavior in the analysis of low molecular weight polymers. A methodology based on non-linear regression of cumulative frequency distributions in polymers has been developed to compare and evaluate different matrix/polymer/cation agent sample combinations for MALDI and PALDl-MS analyses of low molecular weight polymers.

  • 3.
    Woldegiorgis, Andreas
    et al.
    KTH, Superseded Departments, Chemistry.
    Jansson, K.
    Curcio, Mario
    KTH, Superseded Departments, Chemistry.
    Roeraade, Johan
    KTH, Superseded Departments, Chemistry.
    Nanowires for surface enlargement of narrow-bore fused-silica tubing2004In: Electrophoresis, ISSN 0173-0835, E-ISSN 1522-2683, Vol. 25, no 21-22, p. 3660-3668Article in journal (Refereed)
    Abstract [en]

    A method for preparation of silica nanowires with dimensions of d = 10-100 nm, 5-500 nm, is described. The nanostructured material is an integral part of the inner surface of narrow bore fused-silica capillary tubing. The wire preparation method is based on a decomposition of 2-chloro-1,1,2-trifluoroethyl methyl ether at elevated temperature and pressure. The silica bulk material is rearranged via a sustained silica-hydrogen fluoride chemistry, and reaction mechanisms for this process are proposed. The method is suitable for preparing long lengths of tubing with the modified surface. It is our belief that the texture of the capillary wall with its increased surface area is useful for applications such as microreactions, catalysis, and high-resolution pressure and/or electrodriven open-tubular liquid chromatography.

  • 4.
    Woldegiorgis, Andreas
    et al.
    KTH, Superseded Departments, Chemistry.
    von Kieseritzky, Fredrik
    KTH, Superseded Departments, Chemistry.
    Dahlstedt, Emma
    KTH, Superseded Departments, Chemistry.
    Hellberg, Jonas
    KTH, Superseded Departments, Chemistry.
    Brinck, Tore
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry (closed 20110630).
    Roeraade, Johan
    KTH, Superseded Departments, Chemistry.
    Polymer-assisted laser desorption/ionization analysis of small molecular weight compounds2004In: Rapid Communications in Mass Spectrometry, ISSN 0951-4198, E-ISSN 1097-0231, Vol. 18, no 8, p. 841-852Article in journal (Refereed)
    Abstract [en]

    The use of non-polar, small polymers as matrices for the analysis of low molecular weight compounds in polymer-assisted laser desorption/ionization mass spectrometry (PALDI-MS) is demonstrated. The matrices evaluated were either based on an oligothiophene or a benzodioxin backbone. Metallocenes, polycyclic hydrocarbons, a fluorosurfactant, and a subset of small organic compounds with various functionalities, served as model analytes. The mechanism of ionization charge transfer is discussed and ionization potentials for the matrices in the study have been estimated using density functional theory (DFT) calculations. Some of the results are possibly contradictory to the generally accepted limiting conditions for gas-phase charge-transfer reactions. These results are interpreted in the light of energy pooling. Also a new mass calibration procedure for the lowmass region in positive ion mode is presented, and some aspects of the ionization/desorption process leading to radical cations are studied.

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