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andyzhu木虫 (正式写手)
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[求助]
求助稀土配合物荧光的问题
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| 我合成了2个稀土配合物，分别是Ce和Pr的，测它们的荧光时发现配合物不显示稀土离子的荧光，而只显示配体的荧光，这是怎么回事？应该如何解释呢？我这个现象能不能写到我的文章中去呢？相当纠结，烦请大侠们帮帮忙啊。感激不尽啊。 |
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tingting888
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3楼2011-12-22 19:02:58
【答案】应助回帖
andyzhu(金币+8): 你好，能不能把书发给我啊？ 2011-10-12 08:52:16
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1.3.5 The Emission Spectra of Rare Earth Compounds In the 1940s, emissions from rare earth complexes were observed and research into this phenomenon has received growing and lasting attention because of their potential application in optical communications, new generation displays, and sensors. Since the dipole strength of f -f transitions are formally forbidden, typically, these extinction coefficients are of the order of 1 M−1cm−1, an alternative path has to be used which is called luminescence sensitization or antenna effect, that is when the luminescent ion is coordinated with an organic ligand or imbedded into a matrix, then the energy absorbed will be transferred from the surrounding onto the luminescent ion and subsequently the ion emits characteristic light. According to the emission properties, rare earth complexes can be divided into four groups as follows: 1. Sm3+(4f 5), Eu3+(4f 6), Tb3+(4f 8) and Dy3+(4f 9); 2. Pr3+(4f 2), Nd3+(4f 3), Ho3+(4f 10), Er3+(4f 11), Tm3+(4f 12) andYb3+(4f 13); 3. Sm2+(4f 6), Eu2+(4f 7), Yb2+(4f 14) and Ce3+(4f 1); 4. Sc3+(4f 0), Y3+(4f 0), La3+(4f 0), Gd3+(4f 7) and Lu3+(4f 14). For the first group, emissions originate because of the transition of 4f electrons from the lowest excited states to the ground states and the emissions are in the visible region. The probabilities of these transitions are relatively high and strong emissions may be observed. The lifetimes of these emissions are in the microsecond or milliseconds scale. For the second group, the energy levels of these ions are very close to one another. Thus, the emissions are often in the infrared region and their intensities are weaker than those of the first group by several orders of magnitude.All the ions in the third group exist in lower oxidation states and their emissions originate from d–f transitions and not f–f transitions, which would show broader emission bands. Obviously, the ions in the last group all have so-called stable electronic configurations, that is, their 4f orbitals are either “empty,’’ “half-filled’’ or “all-filled.’’ Therefore, no f–f transitions occur except in gadolinium complexes, which emit in the ultraviolet region. However, these complexes do sometimes emit when suitable ligands are coordinated to the central ions. In these cases, the emissions are caused by ligand emission complexes 摘自 RARE EARTH COORDINATION CHEMISTRY |
2楼2011-10-12 08:35:33