Luminescence behavior of terbium sulphosalicylic acid complexes in sol-gel derived host materials

The formation and luminescence behavior of terbium sulphosalicylic acid (TbSSA) complexes in sol-gel derived host materials have been investigated. The 5-sulphosalicylic acid (H3SSA) was dissolved in ethanol in advance, and then the TbCl3 and ethanol containing H3SSA were introduced into the initial precursor sol, respectively. The resulting sol exhibits intramolecular energy transfer from the coordinated sulphosalicylic acid to the terbium ion. The TbSSA complex has formed in the TbCh and H3SSA codoped sol. The complexes were found to have notably higher fluorescence intensities than TbCl3 in both the sol and the gel. In the sol, the concentration quenching was a diffusion-controlled process due to aggregation and effective collision between molecules and the fluorescence was decreased with increase of H3SSA concentration. On the other hand, the molecules in the gel were isolated in the pores of the silica network. The fluorescence intensities of TbSSA in the gel were increased with the increase of concentration ratio of H3SSA/TbCl3. Maximum fluorescence intensity was obtained at H3SSA/TbCl3 = 2.