Synthesis, characterization and luminescence properties of Tb3+ and Eu3+-doped poly(acrylic acid)

Tb3+ and Eu3+-doped poly(acrylic acid) (PAA) was synthesized by polymerization in aqueous solution of the monomer partially neutralized with various amounts of Tb2O3 and Eu2O3, using potassium persulfate as initiator. The monomer modification was confirmed by H-1-NMR. The doped polymer was characterized by H-1-NMR, Fourier transform infrared (FTIR) 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 Eu3+ concentration was increased due to the complex formation. Additionally, the inhomogeneous broadening and the relative intensity of the D-5(0) --> F-7(1,2) transitions of Eu3+ ions, and also, the relatively high intensity of D-5(4) --> F-7(5) green emission of Tb3+, indicate that the dopant ions are uniformly distributed in low symmetry coordination sites. Besides, when both dopants are incorporated to the polymer, the Eu3+ ions quench the luminescence of Tb3+, indicating an efficient energy transfer from Tb3+ to Eu3+ (C) 2002 Elsevier Science B.V. All rights reserved.