Luminescence enhancement of Eu3+-doped poly(acrylic acid) using 1,10-phenanthroline as antenna ligand

Abstract This work reports on the photoluminescence enhancement of Eu 3+ -doped poly(acrylic acid) using 1,10-phenanthroline as antenna ligand. The polymeric material was synthesized by polymerization in aqueous solution of the monomer partially neutralized with Eu 2 O 3 , containing 1,10-phenanthroline, and using potassium persulfate as initiator. The monomer modification and the coordination of antenna ligand to the Eu 3+ ions were confirmed by 1 H-NMR. The doped polymer was characterized by luminescence spectroscopy. The excitation spectra show clear evidence of the coordination between the Eu 3+ ions and the 1,10-phenanthroline ligands in the polymer matrix. On the other hand, the emission spectra show an inhomogeneous broadening and, together with the relative intensity of the 5 D 0 → 7 F 1,2 transitions of Eu 3+ , indicate that the dopant ions are uniformly distributed in low symmetry coordination sites. Besides, an enhancement in the intensity of the Eu 3+ characteristic red emission by 1,10-phenanthroline addition is observed, and it is due to the antenna effect of the ligand, which acts as a sensitizer of the Eu 3+ ions. An estimation of the increasing luminescence efficiency is presented.