Energy Transfer and Emission Quantum Yields of Organic-Inorganic Hybrids Lacking Metal Activator Centers

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• 作者：Só ; nia S. Nobre ; Patrí ; cia P. Lima ; Luí ; s Mafra ; Rute A. S&aacute ; Ferreira ; Ricardo O. Freire ; Lianshe Fu ; Uwe Pischel ; Veró ; nica de Zea Bermudez ; Oscar L. Malta ; Luí ; s D
• 刊名：Journal of Physical Chemistry C
• 出版年：2007
• 出版时间：March 1, 2007
• 年：2007
• 卷：111
• 期：8
• 页码：3275 - 3284
• 全文大小：217K
• 年卷期：v.111,no.8(March 1, 2007)
• ISSN：1932-7455

文摘

This work discusses quantitatively the energy transfer mechanism that occurs in the white-light emission ofsol-gel derived amine- and amide-functionalized hybrids. The white-light photoluminescence (PL) resultsfrom a convolution of the emission originated in the NH/C=O groups of the organic/inorganic cross-linkswith electron-hole recombinations occurring in the siloxane nanoclusters, both emissions typical of donor-acceptor pairs. Two model compounds that reproduce separately the two hybrid's emissions were synthesizedand characterized by X-ray diffraction, ²⁹Si/¹H/¹³C magic-angle spinning NMR, diffuse reflectance, Fouriertransform-IR, and photoluminescence spectroscopy to support their use as organic and inorganic structuralmodels for the two counterparts of the hybrids. The comparison between the lifetimes of the two emissionsof the inorganic and organic model compounds with those of the hybrids, the Arrhenius dependence withtemperature of the siliceous-related lifetime in the hybrids, and the nonexponential behavior of the decaycurve of the siliceous-related emission under lower excitation wavelengths are experimental evidence supportingthe occurrence of energy transfer in the hybrids. This energy transfer rate is quantitatively estimated ford-U(600) (the diureasil host with smaller number of polymer repeat units) generalizing the ideas proposedrecently for the intramolecular energy transfer between singlet and triplet ligand levels and ligand-to-metalcharge transfer states in lanthanide coordination compounds. The dipole-dipole energy transfer rate betweenthe two emitting centers is 1.3 × 10⁹ s^-1, larger than the value estimated for the transfer rate mediated by theexchange mechanism, 3.7 × 10⁸ s^-1. The predicted room-temperature emission quantum yield of that diureasilhybrid is comparable to the corresponding experimental value (7 ± 1 %), pointing out a strong dependenceof the radiative component values of the two emissions with temperature, induced by the glass-rubber phasetransition of the hybrid's polymer chains.