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  • crystallization  (2)
  • silica xerogel  (2)
  • silica xerogels  (2)
  • 13C NMR  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Effect of Pr3+ Doping on the OH Content of Silica Xerogels (1998)
    Springer
    Journal of sol gel science and technology 13 (1998), S. 599-603 
    Details
    ISSN: 1573-4846
    Keywords: silica xerogel ; Pr3+ ; OH contents ; luminescence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Pr2O3-SiO2 xerogels doped with different Pr/Si concentrations were annealed at 900°C for 120 h and then investigated by FTIR, NIR absorption, Raman and luminescence spectroscopies. It is observed that the content of surface silanol groups is lower for higher Pr3+ concentrations. Luminescence measurements indicate that the amount of the residual OH plays an important role in the spectroscopic properties of the Pr3+ ion and in particular the quantum yield of the emission from the 3P0,1 and 1D2 states.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008699412259
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Crystallization of Silica Xerogels: A Study by Raman and Fluorescence Spectroscopy (1997)
    Springer
    Journal of sol gel science and technology 8 (1997), S. 391-395 
    Details
    ISSN: 1573-4846
    Keywords: silica xerogels ; crystallization ; Raman spectroscopy ; Eu3+ luminescence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Pure and europium doped silica xerogels were annealed at 1050°C to obtain full densification, and at 1300°C to induce crystallization. Raman spectroscopy, time resolved selective luminescence and lifetime measurements were performed on glassy and crystallized samples. We discuss the differences between the Raman spectra of the xerogel annealed at 1050°C and those of a commercial silica. The typical Raman structures of α -crystobalite are evident for the 1300°C annealed samples, but a glassy phase coexists, indicating an incomplete crystallization. Fluorescence measurements give information on the environment of the Eu3+ ions in the glassy and crystallized sample.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1026480212567
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Crystallization of silica xerogels: A study by raman and fluorescence spectroscopy (1997)
    Springer
    Journal of sol gel science and technology 8 (1997), S. 391-395 
    Details
    ISSN: 1573-4846
    Keywords: silica xerogels ; crystallization ; Raman spectroscopy ; Eu3+ luminescence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Pure and europium doped silica xerogels were annealed at 1050°C to obtain full densification, and at 1300°C to induce crystallization. Raman spectroscopy, time resolved selective luminescence and lifetime measurements were performed on glassy and crystallized samples. We discuss the differences between the Raman spectra of the xerogel annealed at 1050°C and those of a commerical silica. The typical Raman structures of α-crystobalite are evident for the 1300°C annealed samples, but a glassy phase coexists, indicating an incomplete crystallization. Fluorescence measurements give information on the environment of the Eu3+ ions in the glassy and crystallized sample.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02436871
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Site selection spectroscopy of SiO2:Eu3+ gels (1994)
    Springer
    Journal of sol gel science and technology 2 (1994), S. 783-786 
    Details
    ISSN: 1573-4846
    Keywords: optical spectroscopy ; fluorescence line narrowing ; Eu3+ ; silica xerogel
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Silica gels doped with Eu3+ ions were studied at temperatures between 10 K and 300 K by site selection spectroscopy in samples heated up to 200°C. The 5D0 → 7F0 transition shows internal structures due to the different environments of the europium ions. Lifetimes, energy levels and homogeneous linewidths are site dependent. In the wet gel the Eu3+ ions prefer a liquid-like environment and only when the liquid is removed by heat treatment, the ion is linked more strongly to the silica network.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00486350
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    Complete assignment of the aliphatic chains in dimers, trimers and polymer of 3-hexylthiophene through 2D-NMR spectroscopy (1995)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 33 (1995), S. 657-663 
    Details
    ISSN: 0749-1581
    Keywords: NMR ; 1H NMR ; 13C NMR ; dimers and timers of 3-hexylthiophene ; poly(3-hexylthiophene) ; 1H, 13C inverse detection ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The 1H and 13C signals of the hexyl chains of the title compounds were fully assigned. The regiochemical features of the aliphatic region of proton and carbon spectra were analysed in dimers and trimers. Dimers and trimers proved to be reliable model compounds in the regiochemical assignment of poly(3-hexylthiophene) even when the aliphatic region of proton and carbon spectra was involved. The chemical shifts of the protons of CH2(α)s and of the hexyl chain as a whole and those of the first three aliphatic carbons appear to be the most significant.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1260330807
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    Paper (German National Licenses)
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