Luminescence based on energy transfer in xerogels doped with Ln2−xTbx(WO4)3

This paper presents preparation, optical absorption and photoluminescence properties of luminescent materials consisting of Ln2−xTbx(WO4)3 [where Ln = Gd(III) or La(III)] incorporated into silica xerogel. Photoluminescence behaviour of the salt in the rigid matrix was studied by the luminescence spectroscopy. The excitation spectra of the system Ln2−xTbx(WO4)3 show an intense broad band with a maximum placed at about 240 nm. This band is attributed to ligand–metal charge transfer (LMCT) inside the tungstate group. On the other hand, Tb3+ ion exhibits its characteristic emission in the material. Owing to energy transfer from the excited tungstate groups to the Tb3+ ions the emission intensity is improved. The energy transfer from WO42− group to Tb(III) ion is particularly effective for such dopants as Gd0.4Tb1.6(WO4)3 or La0.8Tb1.2(WO4)3 incorporated into SiO2 xerogel. Concentration of the emission quenchers such as water molecules and OH groups was reduced by thermal treatment. The high emission intensity and easy preparation of these systems make them potential candidates for application as luminescent materials.