Luminescence of Europium(III) and Terbium(III) Complexes Incorporated in Poly(Vinyl Pyrrolidone) Matrix

Abstract

Lanthanide complexes of europium and terbium ions with hydrogen phthalate [Eu(Hphth)3 and Tb(Hphth)3, respectively, Hphth = hydrogen phthalate] were incorporated into poly(vinyl pyrrolidone) (PVP) matrix. Transmission electron microscopy (TEM) results showed that the lanthanide complexes, with a mean diameter about 8.0 nm, were dispersed homogeneously in the PVP matrix. The excitation of the Ln(Hphth)3-PVP system by UV light resulted in a ligand-to-metal energy transfer and the emission spectra of the complexes displayed characteristic luminescence of the central ions. PVP significantly affected the strength of the hypersensitive transitions (5D0 → 7F2 for Eu3+, and 5D4 → 7F5 for Tb3+) of the complexes. For the mixed complexes containing both Eu3+ and Tb3+ as central ions, the luminescent intensity was strongly dependent upon the ratio of the lanthanide ions. Trace amount of Eu3+ quenched the luminescence of the Tb3+, whereas the presence of Tb3+ enhanced the luminescence of the Eu3+, thus demonstrating an important feature of energy transfer from terbium to europium in the mixed complexes.