Synthesis and Luminescent Properties of Rare Earth Gd(III) Doped Eu(III) Complexes with 2,4,6-pyridinetricarboxylic Acid

Doping of non-luminescent rare earth ions into luminescent rare earth complexes is an effective method to enhance their photoluminescent properties. A series of Gd(III) doped Eu(III) complexes were synthesized by hydrothermal method with the ligand of 2,4,6-pyridyl tricarboxylic acid. The ratios of Gd(III) to Eu(III) are 0∶1.0, 0.1∶0.9, 0.2∶0.8, 0.3∶0.7, 0.4∶0.6, 0.5∶0.5, 0.6∶0.4, 0.7∶0.3, 0.8∶0.2, 0.9∶0.1, respectively. The total contents of rare earth ions in the complexes were determined with EDTA standard solution by complexometric titration. And all the complexes were characterized by infrared spectroscopy. The fluorescence excitation spectra, emission spectra, fluorescence lifetime and luminescent quantum yields of the complexes were tested. The effects of gadolinium doping on the luminescence performance of the europium complex were studied. The results show that the optimal excitation wavelength for this series of complexes is 295 nm. When the ratio of Gd(III) to Eu(III) is 0.6∶0.4, the fluorescence of the complex is strongest. Moreover, even when the ratio of Gd(III) to Eu(III) changes from 0.1∶0.9 to 0.8∶0.2, the fluorescence intensity of Gd(III) doped complexes is still stronger than that of pure Eu(III) complexes. When the ratio of Gd(III) to Eu(III) is 0.6∶0.4, the doped complex has the longest fluorescence lifetime and the highest absolute quantum yield of luminescence.