Browsing by Subject "Platinum"

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    DNA-mediated biomineralization of a new planar Pt-complex
    (2006) Klump, H H; Koch, K; Lin, C T
    The crystal growth morphology of a coordination complex of Pt(II) that crystallizes from solution can be controlled by using a second molecular species such as peptides or other organic compounds. Examples of crystal growth controlled by nucleic acids are few. In this article we describe the use of branched three-way junction (3WJ) DNA to influence the crystal growth of a planar platinum compound, cis-[(2, 2′-bipyridyl)N,N-di(2-hydroxyethyl)-N′-benzoylthioureatoplatinum(II)]chloride. Platinum complexes with extended planar aromatic residues are capable of stacking in the absence as well as in the presence of linear DNA double helices. This feature is based on the interaction of the compound with DNA through intercalation, resulting in the prevention of binding of DNA polymerase. Microscopic one-dimensional crystals were observed under these conditions. In the presence of the branched 3WJ DNA, however, additional nucleation sites are present, resulting in extended crystal growth of unique Pt compounds. At least two different crystal modifications were observed using transmission electron microscopy.
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    Influence of preparation variables on the dispersion of platinum on zeolite KL.
    (Elsevier, 1997) M'Kombe, C; Dry, M; O'Connor, C
    Various preparation conditions were investigated to evaluate their effect on the dispersion of Pt on zeolite KL. The highest dispersion was obtained by calcining in O2 at about 350 °C. Calcining in N2 or H2 resulted in lower dispersions. Irrespective of the gas atmosphere, heating at 600 °C resulted in sintering of the Pt. The duration of calcination, whether at 350 °C or 600 °C, had little effect on Pt dispersion. The rate at which the temperature was increased up to the calcination temperature and the rate of the O2 flow also had no effect. Subsequent to identical calcination procedures, reduction with H2 resulted in much higher Pt dispersions than reduction with CO. Below 350 °C the temperature of the H2 reduction did not have a marked effect on dispersion. At the 1.5% Pt level, different loading techniques, viz., liquid ion exchange, solid-state ion exchange, and incipient wetness impregnation, resulted in similar Pt dispersions. There was a good correlation between the percentage of Pt dispersion and n-hexane conversion in the aromatization reaction. Pt dispersions were determined by CO chemisorption, and the observed trends were confirmed by TEM. Hydrogen chemisorption was a less satisfactory method of measuring dispersion. © Elsevier Science Inc. 1997