稀土配合物的时间分辨荧光光谱法研究(Ⅱ)——Eu,Sm-DBM-TOPO体系的荧光衰减动力学特性和激光诱导时间分辨荧光光谱

STUDIES ON TIME-RESOLVED FLUORIMETRY OF RARE EARTH CHELATES(Ⅱ)——THE FLUORESCENT DECAY PROPERTIES AND LASER-INDUCED TIME-RESOLVED FLUORIMETRY OF Eu,Sm-DBM-TOPO SYSTEM

本文以Nd:YAG泵浦的染料激光器为激发光源,门控光学多道分析仪为检测器,自制的触发器和荧光盒组装成一台激光诱导时间分辨光谱装置。采用此装置研究了在表面活性剂Triton X-100存在下铕、钐-二苯甲酰甲烷-三正辛基氧化膦(Eu、Sm-DBM-TOPO)体系的激光诱导发光光谱特性和荧光衰减动力学特性。讨论了荧光发射过程中的能量传递机制。拟定出测定痕有铕和钐的时间分辨光谱方法,用于高纯稀土氧化物等样品中痕量铕和钐的测定,结果满意。

In this paper, a multifunctional laser-induced time-resolved fluori-meter is described. Basic components of the device are: anactive Q-swit-ched Nd:YAG pumped dye laser(YG581/TDL50) as the excitation light source, a gated vidicon optical multichannel analyzer(WPl/WP2) as the fluorescence detecting equipment, and a electric trigger which made by our laboratory as the external trigger source. The applied software and interface between IBM PC/XT computer and the fluorimeter are designed for data acquisition and data processing of fluorescent spectra.Using the output of frequency tripling of Nd:YAG laser(355nm),the DBM(dibenzoylmethane) produces very much weaker luminescence in 430-510nm, whereas TOPO(tri-n-octylphosphine oxide) has much stron- ger luminescence in 365-430nm. The data of luminescence lifetime demonstrate that the luminescence of DBM and of TOPO are phosphorescence and fluorescence, respectively. However, the fluorescence emission of TOPO decreased remarkably in the presence of DBM. The sharp line emission of RE-DBM-TOPO systems is observed, Eu-DBM-TOPO and Sm-DBM-TOPO show very intense emission, whereas Tb-DBM-TOPO shows very weak emission in high concentration. The fluorescence emissions of RE-DBM are very much weaker than those of RE-DBM-TOPO, but the characteristic emissions aren't observed in RE-TOPO. The fluorescence lifetimes of Eu-DBM, Eu-DBM-TOPO, Sm-DBM and Sm-DBM -TOPO are measured to be 100, 500, 32 and 45us at room temperature using this device, respectively. The fluorescence lifetmes are similar for the different characteristic emission of each chelate. The fluorescence decay curves show exponential decay process for fluorescenc emission of RE-DBM and nonexponential decay process for fluorescence emission of RE-DBM-TOPO.From above pieces of information, a mechanism of energy transfer is proposed. The energy transfers from the donor TOPO to the acceptor DBM and from donor DBM to the rare earth ions. The DBM acts both the donor and acceptor. RE-DBM-TOPO+2hv-RE-DBM*-TOPO*-RE*-BBM*-TOPO-RE*-DBM-TOPO+hu.The process can be described as -RE-DBM-TOPO +hv.It is difficult to detect the trace of europium in a large excess if samarium by means of steady-state fluorimetry,because the fluorescence intensity of Eu-DBM-TOPO is markedly enhanced at 614nm. The sampling delay time is set to 300μs so as to determine the fluorescence signal of Eu-DBM-TOPO in the existence of large amounts samarium. The proposed method is used to determin simultaneously the trace of europium and samarium in highly pure rare earth oxides without preseparation.