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)(3)Eu) rather than a traditional nitrate (Eu(NO3)(3) . 6H(2)O) 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)(3)Al is found to be as effective at inhibiting Eu3+ clustering as the previously reported Al(NO3)(3) . 9H(2)O and (C4H9O)(2)Al-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.