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

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.