Energy Transfer Mechanisms in Organic-Inorganic Hybrids Incorporating Europium(III): A Quantitative Assessment by Light Emission Spectroscopy

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• 作者：Patrí ; cia P. Lima ; Só ; nia S. Nobre ; Ricardo O. Freire ; Severino A. Jú ; nior ; Rute A. Sá ; Ferreira ; Uwe Pischel ; Oscar L. Malta ; Luí ; s D. Carlos
• 刊名：Journal of Physical Chemistry C
• 出版年：2007
• 出版时间：November 29, 2007
• 年：2007
• 卷：111
• 期：47
• 页码：17627 - 17634
• 全文大小：166K
• 年卷期：v.111,no.47(November 29, 2007)
• ISSN：1932-7455

文摘

This work discusses quantitative aspects of energy transfer occurring in sol-gel derived organic-inorganicdi-ureasil hybrids incorporating either [Eu(btfa)₃(4,4'-bpy)(EtOH)] (btfa = benzoyltrifluoroacetonate, 4,4'-bpy = 4,4'-bipyridine) or Eu(CF₃SO₃)₃. Host-to-Eu³⁺ energy transfer occurs either via ligand singlet andtriplet (T) excited states or directly from the hybrid emitting centers through the dipole-dipole, dipole-2pole ( = 2, 4, and 6) and exchange mechanisms. This latter process is dominant for all discussed energytransfer pathways. The ligand-to-Eu³⁺ energy transfer rate is typically 1 order of magnitude larger than thevalue estimated for direct hybrid-to-Eu³⁺ transfer (3.75 × 10¹⁰ and 3.26 × 10⁹ s^-1, respectively, to the ⁵D₁level). The most efficient luminescence channel is (S₀)_Hybrid (T)_Hybrid (T)_Ligand (⁵D₁, ⁵D₀) ⁷F_0-6. Thepredicted emission quantum yield of the di-ureasil incorporating [Eu(btfa)₃(4,4'-bpy)(EtOH)] is in excellentagreement with the corresponding experimental value (53 and 50 ± 5%, respectively), pointing out that theoptimization of the ground state geometry by the Sparkle/AM1 model can, under certain conditions, beimplemented in Eu³⁺-based organic-inorganic hybrids. For di-ureasils incorporating Eu(CF₃SO₃)₃, the energytransfer rates could not be quantitatively predicted because of the higher computational effort necessary forcalculating the singlet and triplet excited states in complex structures, such as these di-ureasils. Instead, theclassic Förster and Dexter approaches were applied. Although less efficient, as compared with the di-ureasilincorporating [Eu(btfa)₃(4,4'-bpy)(EtOH)], the hybrid-to-Eu³⁺ energy transfer is also dominated by the exchange(Dexter) interaction.