Immobilization of lanthanide ions in a pillared layered double hydroxide
Immobilization of lanthanide ions in a pillared layered double hydroxide
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DOI：
10.1021/cm051431p
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发表时间：
2005-11-15
影响因子：
8.6
通讯作者：
Gonçalves, IS
中科院分区：
文献类型：
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作者：
Gago, S;Pillinger, M;Gonçalves, IS
以2，2 '-联吡啶-5，5'-二羧酸根（BDC）柱撑的Zn-Al层状双氢氧化物（LDH）为多孔基质，对LnCl（3）（Ln = Eu，Gd）进行插层。实现了Eu的9.0重量%和Gd的11重量%的金属负载，这对应于每三个BDC离子约两个镧系离子。对含铕材料的室温Eu L-3边EXAFS的拟合揭示了在2.41埃处的7 +/- 1个氧/氮原子的壳层。该材料的发射光谱显示出典型的Eu ~（3+）红光发射和460 nm附近的宽带峰，这是由于未与Eu ~（3+）配位的自由配体的三重态发射所致。在不同的激发波长下，并在低温下的发射光谱的测量表明，只有一种类型的Eu 3+结合位点的存在。D-5（0）量子效率估计为低（7.7%），这是由于第一配位壳层中存在水分子引起的相对高的非辐射跃迁概率。水分子的数目计算为3.6 +/- 1，表明掺入的铕离子是6-配位的，其中四个氧原子来自水分子，两个氮原子来自二齿联吡啶配体。
A Zn-Al layered double hydroxide (LDH) pillared by 2,2'-bipyridine-5,5'-dicarboxylate (BDC) anions was used as a porous matrix to intercalate LnCl(3) (Ln = Eu, Gd). Metal loadings of 9.0 wt% for Eu and 11 wt% for Gd were achieved, which correspond to about two lanthanide ions for every three BDC ions. The fitting of the room-temperature Eu L-3-edge EXAFS for the europium-containing material revealed one shell of 7 +/- 1 oxygen/nitrogen atoms at 2.41 angstrom. No evidence for a Eu-Cl bond was found. The emission spectra for this material display the typical Eu3+ red emission and a large broad band peaking around 460 nm, which was attributed to the emission arising from the triplet levels of free ligands not coordinated to Eu3+ ions. Measurement of the emission spectra under different excitation wavelengths and also at low temperature showed the existence of only one type of Eu3+ binding site. The D-5(0) quantum efficiency was estimated to be low (7.7%), due to a relatively high nonradiative transition probability caused by the presence of water molecules in the first coordination shell. The number of water molecules was calculated as 3.6 +/- 1, suggesting that the incorporated europium ions were 6-coordinate with four oxygen atoms from water molecules and two nitrogen atoms from a bidentate bipyridyl ligand.