The in situ synthesis process and luminescence behavior of 2-pyridinecarboxylic acid europium complexes in the sol–gel derived host materials

The in situ synthesis processes and luminescence behaviors of the 2-pyridinecarboxylic acid europium (PA:Eu3+) complexes in sol–gel derived host materials have been investigated. The Raman scattering spectrum of the 1 mol% EuCl3 and 3 mol% PA co-doped gel was similar to that of the PA:Eu3+ complex powders that were synthesized in ethanol, which indicated that the PA:Eu3+ complexes have been in situ synthesized in the 1 mol% EuCl3 and 3 mol% PA co-doped gel. The excitation and the emission spectra of the 1 mol% EuCl3 and 3 mol% PA co-doped gels, which were similar to that of the PA:Eu3+ complex powders, also indicated an efficient ligand-to-metal energy transfer which belonged to the complexes. The decay curve of the 1 mol% EuCl3 and 3 mol% PA co-doped gel can be fitted to a double-exponential function. After the gel was heated at 90 °C for 12 h, the decay curve can be fitted to a single-exponential function due to vaporization of the most residual water in the gel. The dependence of luminescence intensity and the decay time of x% EuCl3 and 3x% PA co-doped gels that were heated at 90 °C for 12 h on various concentrations of the EuCl3 and PA were also investigated. The luminescence intensity and the decay time reached a maximum for 1 mol% EuCl3 and 3 mol% PA co-doped gel that were heated at 90 °C for 12 h.