Judd–Ofelt analysis of lanthanide doped silica–PEG hybrid sol–gels

Abstract

Lanthanide complexes of 1,10-phenanthroline (phen), 2,2′-bipyridine (bipyridyl, bpy) and dipicolinate (dpa), together with uncomplexed lanthanide ions (Ln = Nd, Sm, Dy, Ho, Er) were doped into silica–polyethylene glycol (SiO₂–PEG) inorganic–organic hybrid materials. The samples were prepared via a sol–gel process. The intensities of the f–f transitions in the absorption spectrum were analysed by application of the Judd–Ofelt theory. Sets of phenomenological Ω_λ intensity parameters have been extracted. The hypersensitive transitions are strongly influenced by the drying time of the sol–gel glass. The PEG molecules compete with the organic ligand for complex formation to the lanthanide ions complex. 1,10-Phenanthroline and bipyridyl complexes are not stable in the presence of PEG, but the dipicolinate complexes are.