Browsing by Subject "Cation"

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    ItemOpen Access
    Investigation of binding properties of dicationic styrylimidazo[1,2-a]pyridinium dyes to human serum albumin by spectroscopic techniques
    (John Wiley and Sons Ltd, 2017) Özdemir, A.; Gökoğlu, E.; Yılmaz, Esra; Yalçın, E.; Gökoğlu, E.; Seferoğlu, Z.; Tekinay, T.
    The binding interaction between two dicationic styrylimidazo[1,2-a]pyridinium dyes and human serum albumin (HSA) was investigated at physiological conditions using fluorescence, UV–vis absorption, and circular dichroism (CD) spectroscopies. Analysis of the fluorescence titration data at different temperatures suggested that the fluorescence quenching mechanism of HSA by these dyes was static. The calculated thermodynamic parameters (ΔG°, ΔH° and ΔS°) indicated that hydrogen bonding and van der Waals forces played a major role in the formation of the dye–HSA complex. Binding distances (r) between dyes and HSA were calculated according to Förster's non-radiative energy transfer theory. Studies of conformational changes of HSA using CD measurements indicate that the α-helical content of the protein decreased upon binding of the dyes.
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    ItemOpen Access
    Sorption of phenol and radioactive cesium onto surfactant modified insolubilized humic acid
    (2010) Celebi, O.; Erten, H. N.
    In this study, the sorption behavior of two important contaminants, phenol and radioactive cesium (137Cs), onto surfactant modified insolubilized humic acid (SMIA) were investigated as a function of time, sorbate concentration utilizing the radiotracer method and UV-Vis spectroscopy. Phenol sorption process was well described by both Freundlich and Tempkin type isotherms, and cesium sorption was described by Freundlich and Dubinin-Radushkevich isotherms. It was found that SMIA adsorbs both cations and phenolic substances. Kinetic studies indicated that adsorption behavior of phenol obey the pseudo second order rate law. FTIR spectroscopic technique was used to understand the structural changes during modification process with surfactants.
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    ItemOpen Access
    Spectroscopic characterization of vanadium(v) oxo species deposited on zirconia
    (Royal Society of Chemistry, 2000) Kantcheva, M.
    A method for deposition of vanadium(v) oxo species from acidic solutions of ammonium metavanadate on zirconia is described. The samples are synthesized by suspension of the support (powder) in solutions containing three different vanadium(V) precursor ions: the dioxovanadium(V) ion, VO2+, the yellow diperoxo anion [VO(O-O)2]- and the red monoperoxo cation [VO(O- O)]+. Application of vanadium(V) peroxo complexes increases significantly the uptake of vanadium by zirconia. The state and localization of the VO(x) species on the surface of zirconia were studied by FTIR, UV/VIS and XP spectroscopies. The materials prepared from VO2+ ions contain isolated VO4 groups and domains of orthovanadate species, (VO4)(n). The FTIR spectra of adsorbed CO revealed that the number of exposed Zr4+ ions decreased markedly when vanadium(v) peroxo ions were used as precursors. The predominant surface structure in this case was identified as pyrovanadates, V2O7. On all of the samples studied no separate phase of V2O5 was detected.