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  • 1
    ISSN: 0886-9383
    Keywords: Derivatization reaction ; Factorial design ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A number of nucleophiles have been successfully identified and quantified using the Kröhnke reaction with 2,3-diphenyl derivatives of quinolizinium salts. Optimization of the reaction conditions by means of a mathematical model involving analysis of the response surface has led to a better understanding of the factors exerting an influence on the above reaction.The parameters chosen were temperature, reaction time, base concentration, water concentration and nucleophile concentration. The reaction was developed in polar aprotic solvents (acetone, acetonitrile). To facilitate the nucleophilic attack, the presence of an organic base (triethylamine) was necessary, although concentrations in excess of 0·15M did not alter the development of the reaction. Since pharmaceutical solutions are often aqueous, the influence of water on the reaction was studied. Low water volumes have no significant influence on the opening of the quinolizinium ring by the nucleophilic reagent. However, when the water proportion exceeded that of the organic solvent, the fluorescence intensity was lower than expected. Development of the fluorescent reaction product was first detected 5 min after the reaction started. The fluorescence intensity reached its optimum value after 138 min.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Thin films of TiNx with 0.34〈x〈1.19 were deposited on silicon substrates by a filtered arc deposition process. Spectroscopic ellipsometry (SE) in the energy region 1.5-3.5 eV was used to measure the optical properties of the films. X-ray photoelectron spectroscopy (XPS) was used to determine the relative atomic concentration and the chemical states of the elements. The dielectric function ε(ω) measured by ellipsometry gives the optical response of TiNx films and valuable information on their chemical composition, which is also verified by XPS. The plasma energy ωp of TiNx films was found to depend strongly on the N/Ti ratio and this is correlated with the value of x as determined by XPS and Rutherford backscattering spectroscopy (RBS). The results show that, via the calibration, spectroscopic ellipsometry may be used to estimate the stoichiometry of deposited TiNx films.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 10 (1987), S. 13-16 
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Low energy ISS has been used to investigate, in situ, thin films of zirconium dioxide deposited by evaporation and ion-assisted deposition. It is shown that when a film is deposited to an average thickness of 0.3 nm ± 0.03, as measured by in situ ellipsometry, complete coverage of the substrate occurs. Ion-assisted films have detectably higher Zr surface concentrations and reduced low-energy sputter peaks. Inelastic tailing effects in the Zr scattering peak for 2 keV 4He+ are found to come from particles scattered from approximately the first 7 nm of the oxide surface. The influence of primary ion energy on the Zr/O ratio is also examined.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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