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

This work discusses quantitative aspects of energy transfer occurring in sol−gel derived organic−inorganic di-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 and triplet (T) excited states or directly from the hybrid emitting centers through the dipole−dipole, dipole−2λ pole (λ = 2, 4, and 6) and exchange mechanisms. This latter process is dominant for all discussed energy transfer pathways. The ligand-to-Eu3+ energy transfer rate is typically 1 order of magnitude larger than the value estimated for direct hybrid-to-Eu3+ transfer (3.75 × 1010 and 3.26 × 109 s-1, respectively, to the 5D1 level). The most efficient luminescence channel is (S0)Hybrid → (T)Hybrid → (T)Ligand → (5D1, 5D0) → 7F0-6. The predicted emission quantum yield of the di-ureasil incorporating [Eu(btfa)3(4,4‘-bpy)(EtOH)] is in excellent agreement with the corresponding experimental v...

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