稀土三元配合物粉末和凝胶共发光效应的光声光谱研究

Photoacoustic Study of the Co-fluorescence Effect of Lanthanide Ternary Complexes in Solid States

合成了Eu(TTA) 3 ·Phen和Eu0 .8Y0 .2 (TTA) 3 ·Phen固体配合物微晶粉末及其掺杂的SiO2 凝胶样品 .在30 0～ 80 0nm测定并解释了其光声光谱 .在配体吸收处 ,Eu0 .8Y0 .2 (TTA) 3 ·Phen的光声强度低于Eu(TTA) 3 ·Phen的光声强度 ;而对于配合物掺杂的凝胶样品 ,则情况相反 .Y3 + 的引入改变了配合物的弛豫过程 ,且配合物在粉末和凝胶状态下 ,弛豫历程不尽相同 .结合荧光光谱研究了标题化合物的发光特性 ,并建立了能量传递模型 .

Eu(TTA) 3·Phen and Eu 0.8 Y 0.2 (TTA) 3·Phen (TTA: thenoyltrifluoroacetone; Phen: phenanthroline) complex powders and their doped silica gels are synthesized. At the room temperature, their photoacoustic (PA) spectra are recorded and interpreted in the region of 300～800 nm. The PA intensities of central rare earth ions are interpreted by the probability of nonradiative transitions. It is found that the PA intensity of the ligand bears a relation to the molecular energy transfer processes. In the region of ligand absorption, PA intensity of Eu(TTA) 3·Phen is stronger than that of Eu 0.8 Y 0.2 (TTA) 3·Phen for complex powders. While for the PA intensity of the complexes in silica gels, the reverse is true. This indicates that the addition of Y 3+ changes the relaxation processes of europium ternary complex and that the relaxation processes of ternary complexes are different in the two kinds of solid states. The changes of fluorescence spectra turn out to be complementary to the PA spectra. According to Foster and Dexter'stheories, energy can be transferred to moleculesat short distances by intermolecular energy transfer. The efficiency of the intermolecular energy transfer is dependent on close approach or contact of the donor to the acceptor. Eu 0.8 Y 0.2 (TTA) 3·Phen was prepared by coprecipitation. The short distance between molecules in the coprecipitate makes the intermolecular energy transfer possible. In Eu 0.8 Y 0.2 (TTA) 3·Phen coprecipitate powder, Y 3+ has no low-lying 4f energy levels, so that the energy absorbed by its complex molecules cannot be dissipated through these energy levels, but is transferred to the nearby molecules Eu(TTA) 3·Phen in the aggregated particles which results in the characteristic emissions of Eu 3+ . Thus the luminescence of Eu 3+ is enhanced by an intermolecular energy transfer process. R=0.87 for Eu 0.8 Y 0.2 (TTA) 3·Phen indicates that the probability of radiative transitions increases with addition of Y 3+ . In the silica gel doped with Eu 0.8 Y 0.2 (TTA) 3·Phen, Eu(TTA) 3·Phen and Y(TTA) 3·Phen, complex molecules are trapped in the pores and isolated from each other. The distance between the molecules is too long to induce an intermolecular energy transfer. So, the fluorescence intensity of Eu 3+ decreases with the replacement of emission ion Eu 3+ by Y 3+ . R =1.23 for Eu 0.8 Y 0.2 (TTA) 3·Phen in silica gel indicates that the probability of nonradiative transitions increases with the addition of Y 3+ . The model for energy transfer processes is established.