Experimental And Theoretical Studies On The J-O Parameters Of Lanthanide (Europium Ⅲ) Organic Complex

Compounds containing rare earth ions have long been used as fluorescent and laser materials due to their sharp intensely luminescent f-f electronic transitions. Unfortunately, since the f-f transitions of rare earth ions are forbidden by the selection rule, they absorb very little excitation energy. Photoactive rare earth organic complex exhibits intense narrow emission band via an effective intramolecular energy transfer from the ligands to the metal ions under excitation by near ultraviolet light, which is called the antenna effect. Therefore, they are expected to be promising luminescent dopants for the preparation of hybrid fluorescent and other optical sources.However, most of the researches works concerning lanthanide b-diketonate chelates have been mainly focused on the solid complexes themselves and the practical applications of organic rare earth complexes are hindered by their weaknesses such as thermal and luminescence stability et al. A variety of approaches have been developed to overcome the above-mentioned weaknesses and to enlarge their application range.The synthesis of polymer composite materials containing lanthanide organic complexes is an important approach to the preparation of photoelectric functional materials. In the synthetic process, the partial polar group in polymer chains is able to replace some micro-molecule ligand (such as water) in lanthanide complex occurring interaction with lanthanide ion, leading to the profound effect of the structure and performance of lanthanide polymer composite materials.Judd-Ofelt obtained the relationship between crystal field and the transition intensity based on the configuration mixing theory, and built up a method for calculating the transition intensity parameters from the absorption spectra. But the use of J-O theory is limited, because in many cases the measurement of absorption spectra is difficult.In this paper, J-O theory was used to analyze the emission spectra of rare earth ions of Eu³⁺, the copolymer system of styrene/α-methyl acrylic acid which can coordinate with lanthanide and possess polymeric activity was selected. Novel composite resins possessing good luminescent properties have been synthesized through a free radical copolymerization of styrene,α-methyl acrylic acid and the binary or ternary complexes of lanthanide ions (Eu³⁺). We characterized the molecular structure, physical and mechanical performance, and the luminescent properties of the composite resins. Spectra investigations indicated thatα-methyl-acrylic acid act as both solubilizer and coligand. Photoluminescence measurement indicated that the lanthanide complexes show superior emission lines and higher intensities in the resin matrix than in the corresponding pure complex powders (although the complex content in copolymer system is only 0.31wt %). The phenomenon can be attributed to the restriction of molecular motion of complexes by the polymer chain networks and the exclusion of water molecules from the complex. These results indicated that these composite resins possessed better transparency (80～89%) and mechanical performance.