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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Journal of sol gel science and technology 2 (1994), S. 387-391 
    ISSN: 1573-4846
    Keywords: BaO-TiO2-SiO2 gel ; homogeneity effect ; crystallization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract In BaO-TiO2-SiO2 system, crystallization from various gel by heating depended on the sol-gel processes and gel homogeneity. Through the condensation reaction of Si(OAc)4 and TiAcAc(O i Pr)3 in tetrahydrofuran solvent, homogeneous TiO2-SiO2 sol with oligomers of relatively large molecular weight was obtained. The gel prepared by mixing the binary sol, Ba(OAc)2, and Si(OMe)4 was the most homogeneous in term of suppression of crystallization. By heating the above gel, only Ba2TiSi2O8 crystal appeared, which was observed in a melt quenched glass. In the case of the gels made by other sol-gel processes, TiO2 or BaTiO3 crystal was first observed from the heated gels prior to the precipitation of Ba2TiSi2O8.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Journal of sol gel science and technology 4 (1995), S. 67-73 
    ISSN: 1573-4846
    Keywords: photostability of laser-dye ; inorganic-organic matrix ; optical solid material ; fluorescence decay ; mobility of dye
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The laser dye, 4-dicyanomethylene-2-methyl-6-p-dimethylaminostyryl-4H-pyran (DCM) was incorporated in various inorganic-organic host matrices by the sol-gel technique. The photostability of the DCM-doped materials under CW argon laser irradiation was investigated. The absorption of DCM monomer ar 480 nm decreased with increasing irradiation time and was accompanied by an increase in the absorption at 352 nm by inactive photoproducts. Photostability was estimated by measuring the decay rates of DCM fluorescences in different host matrices. The rates exhibited two components; a rapid decay within the first several tens of seconds followed by a slower luminescence decay. The rapid decay depended upon the DCM content in the matrix while the slow decay component was related to the mobility of the DCM in the different matrices. The silica host matrix containing phenyl and a small amount of epoxy groups exhibited the best photostability of the materials examined.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Journal of sol gel science and technology 2 (1994), S. 755-759 
    ISSN: 1573-4846
    Keywords: monomer dispersion in spheres ; photochemical hole burning ; microcavity effect
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Organic dyes such as water soluble porphyrins were incorporated into monodispersed SiO2 particles using the sol-gel technique (the Stober synthesis) and their monomeric and dimeric properties were investigated by aiming at the microcavity effect. Doping efficiencies of dyes into SiO2 particles depended on dye's hydrophilic properties. The doping efficiency of a porphyrin, TTMAPP, decreased with increasing the nominal content in the starting solution and the doping content showed the maximum value of 1.6×10−5 mol/g SiO2. With increasing the TTMAPP content, spectra of doped particles were changed from dimeric to monomeric nature; the absorption peak due to dimers disappeared and halfwidth of absorption at Soret band decreased. This unusual change was caused by the decrease of particle sizes by dye doping. The TTMAPP-doped sample having monomeric spectrum showed the fluorescence life time of 8.5 nsec and photochemical hole burning at about 5 K.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Journal of sol gel science and technology 2 (1994), S. 457-460 
    ISSN: 1573-4846
    Keywords: thick film ; interfacial polymerization ; optical waveguide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A silicate glass film of 2–20 µm in thickness has been formed on a fused quartz substrate by a sol-gel process using an interfacial polymerization technique. A partially hydrolyzed silicon alkoxide was dissolved in hexane and brought into contact with ammonia water in a cylindrical Teflon container. A silica gel film formed at the interface between the two immiscible liquids by the polycondensation of the partially hydrolyzed silicon alkoxide was gently placed on a substrate at the bottom of the container, by draining the liquid. The crack free gel film was dried in an ambient atmosphere and dip-coated with boron ethoxide, followed by sintering in an oven at 1250°C for 1 h. The glass film thus obtained was highly transparent and 2–20 µm in thickness depending on the concentration of the precursor solution and the pH of ammonia water.
    Type of Medium: Electronic Resource
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