In Situ Dehydroxylation in Eu³⁺-Doped Sol−Gel Silica

Abstract

Fluorescence line narrowing and lifetime measurements are used to characterize the extents of clustering and hydroxyl quenching, respectively, in Eu3+-doped sol−gel silica glasses prepared using europium trifluoromethanesulfonate (triflate). A triflate ((CF3SO3)3Eu) rather than a traditional nitrate (Eu(NO3)3·6H2O) precursor is used as the rare earth ion dopant in order to determine the feasibility of effecting chemical dehydroxylation via in situ fluorination by incorporating fluorine directly as a ligand substituent of the Eu3+ precursor. In samples doped only with Eu3+, the use of the triflate precursor leads to no noticeable differences in hydroxyl quenching of Eu3+ fluorescence or Eu3+ aggregation relative to samples prepared with a nitrate precursor. Beneficial effects are observed, however, in samples codoped with Al3+ or Sr2+. When Al3+ or Sr2+ is included in the synthesis, a reduction in hydroxyl quenching of Eu3+ is observed when the triflate precursor is used relative to the nitrate precursor. In addition, (CF3SO3)3Al is found to be as effective at inhibiting Eu3+ clustering as the previously reported Al(NO3)3·9H2O and (C4H9O)2Al−O−Si(OC2H5)3 precursors. The effect of incoporating fluorine via FSi(OC2H5)3 is also briefly considered and gives mixed results which differ for nitrate and triflate Eu3+ precursors.

Titanium Dioxide Nanomaterials: Basics and Design, Synthesis and Applications in Solar Energy Utilization Techniques

“…On the other hand, the great mismatch of ionic radius between Eu 3+ (0.95 Å) and Ti 4+ (0.68 Å) makes the doping Eu 3+ hardly enter into the TiO 2 lattice (Lin & Yu, 1998), but inclined to distribute in the crystallite surface or interstitials of TiO 2 nanocrystals. For the poorcrystallized TiO 2 matrix, the Eu 3+ has a tendency to form clusters due to the reduction of Eu 3+ −Eu 3+ distances (Stone et al, 1997). The clusters are undesirable which lead to an enhanced interparticle contact of the Eu−Eu pairs, thus quench its luminescence through cross relaxation.…”

5D3→7FJ emission in terbium-doped sol–gel glasses

“…RE clustering has been studied with fluorescence line narrowing (FLN)-a laser technique that allows the detection of energy migration among the Eu 3+ ions [7,8]. While the FLN experiments on sol-gel materials doped with Eu 3+ have demonstrated differences in the degree of energy migration between samples containing Eu 3+ clusters and samples with uniform doping, the details of the dynamics have proven to be difficult to extract [4].…”

Characterization and photoluminescence properties of aluminum borate nanorods doped with Eu

“…10 It is relatively easy to analyze the linear spectrum of Eu 3+ since the strongest transition which originates from an energy state is not split by the crystal field. It is well known that Eu 3+ ion is supersensitive to the evolution of its surroundings, [11][12][13] therefore it is favorably a good probe for the investigation of the local structure. Compared with the linear spectrum of Eu 3+ , the emission and absorption spectra of Eu 2+ ion usually consist of broadbands and the luminescence is very strongly dependent on the host lattice, which is quite different from the Eu 3+ ion.…”