Synthesis, characterization and luminescence properties of Tb 3+ and Eu 3+-doped poly(acrylic acid)

Abstract

Tb 3+ and Eu 3+-doped poly(acrylic acid) (PAA) was synthesized by polymerization in aqueous solution of the monomer partially neutralized with various amounts of Tb 2O 3 and Eu 2O 3, using potassium persulfate as initiator. The monomer modification was confirmed by 1H-NMR. The doped polymer was characterized by 1H-NMR, Fourier transform infrared (FT-IR) and luminescent spectroscopy. The NMR and FT-IR results show clear evidence of the coordination between the dopant cations and the carboxylate anions, which are formed during the partial neutralization of the monomer prior to polymerization. On the other hand, the polymer phosphorescence intensity decreased as the Eu 3+ concentration was increased due to the complex formation. Additionally, the inhomogeneous broadening and the relative intensity of the 5D 0→ 7F 1,2 transitions of Eu 3+ ions, and also, the relatively high intensity of 5D 4→ 7F 5 green emission of Tb 3+, indicate that the dopant ions are uniformly distributed in low symmetry coordination sites. Besides, when both dopants are incorporated to the polymer, the Eu 3+ ions quench the luminescence of Tb 3+, indicating an efficient energy transfer from Tb 3+ to Eu 3+.