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Photoacoustic Study of the Co-fluorescence Effect of Lanthanide Ternary Complexes in Solid States
Yang Yuetao*,Su Qingde,Zhang Shuyi
Author NameAffiliationE-mail
Yang Yuetao* State Key Laboratory of Modern Acoustics, Institute of Acoustics, Nanjing University, Nanjing 210093 yyang@nju.edu.cn 
Su Qingde Department of Chemistry, University of Science and Technology of China, Hefei 230026  
Zhang Shuyi State Key Laboratory of Modern Acoustics, Institute of Acoustics, Nanjing University, Nanjing 210093  
Abstract:
Eu(TTA)3·Phen and Eu0.8Y0.2(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 Eu0.8Y0.2(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 Y3+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’s theories, energy can be transferred to molecules at short distances by inter-molecular energy transfer. The efficiency of the intermolecular energy transfer is dependent on close approach or contact of the donor to the acceptor. Eu0.8Y0.2(TTA)3·Phen was prepared by coprecipitation. The short distance between molecules in the coprecipitate makes the intermolecular energy transfer possible. In Eu0.8Y0.2(TTA)3·Phen coprecipitate powder, Y3+ 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 Eu3+. Thus the luminescence of Eu3+ is enhanced by an intermolecular energy transfer process. R=0.87 for Eu0.8Y0.2(TTA)3·Phen indicates that the probability of radiative transitions increases with addition of Y3+. In the silica gel doped with Eu0.8Y0.2(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 Eu3+ decreases with the replacement of emission ion Eu3+ by Y3+. R=1.23 for Eu0.8Y0.2(TTA)3·Phen in silica gel indicates that the probability of nonradiative transitions increases with the addition of Y3+. The model for energy transfer processes is established.
Key words:  Photoacoustic spectroscopy, Lanthanide ternary complex, Co-fluorescence effect, Silica gel
FundProject:国家自然科学基金资助项目(10174038).
稀土三元配合物粉末和凝胶共发光效应的光声光谱研究
杨跃涛*,苏庆德,张淑仪
摘要:
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300~800nm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.
关键词:  光声光谱  稀土三元配合物  共发光效应  SiO2凝胶
DOI:10.1088/1674-0068/15/2/137-140
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