稀土配合物掺杂凝胶的原位光声光谱研究及其共发光效应

采用溶胶-凝胶方法，制备了Ln(Sal)₃·H₂O(Ln3+∶La3+, Nd3+, Tb3+; Sal: 水杨酸) 稀土配合物掺杂的二氧化硅凝胶样品。首次采用光声光谱对稀土配合物在凝胶中的形成进行研究。结果表明，经110 ℃热处理后，Tb3+, La3+和Nd3+配合物掺杂的凝胶样品在配体吸收处的光声强度依次明显增强；而对仅在室温陈化、干燥的湿凝胶样品，其配体吸收处的光声强度几乎完全相同。研究发现，未经适当的热处理过程凝胶样品中稀土配合物尚不能形成。结合荧光光谱，分析了凝胶中稀土离子配位环境的变化和稀土配合物的形成。首次发现了稀土芳香羧酸配合物掺杂凝胶的共发光效应，考察Tb_0.8Gd_0.2(Sal)₃·H₂O和Tb_0.8Nd_0.2(Sal)₃·H₂O配合物掺杂的凝胶样品，发现Gd3+离子的引入了增强了凝胶样品中Tb3+的发光效率，而Nd3+离子的引入明显减弱了凝胶中Tb3+的发光，并对共发光效应可能的机理进行了讨论。

Study of Lanthanide Complexes-Doped Silica Gels and the Co-fluorescence Effect by Photoacoustic Spectroscopy in Situ

Silica matrices, due to their good optical, thermal and chemical properties, are suitable candidates for the hosts of luminescent lanthanide complexes. However, lanthanide complexes would be unstable in the most common sol-gel precursor solution. It is important to study the coordination environment of lanthanide ions and the formation of lanthanide complexes in silica gels. In the present work, lanthanide complexes Ln(Sal)₃·H₂O(Ln3+∶La3+, Nd3+ and Tb3+; Sal: salicylic acid) were incorporated into silica gels via a sol-gel process. PA technique was firstly used to monitor the formation of lanthanide complexes in silica gels. Upon heat treatment at 110 ℃, PA intensity of the ligand increased for Tb3+, La3+ and Nd3+ complexes in silica gels, respectively, while this difference could not be observed for the wet gels (samples without heat treatment). By comparison with fluorescence spectra, experimental data indicate that lanthanide complexes decompose in wet gels. The formation of lanthanide complexes in silica gels is discussed from two aspects: radiative and nonradiative processes. Co-luminescence effect was found for lanthanide complexes with aromatic carboxylic acid doped silica gels for the first time. For Tb_0.8Ln_0.2(Sal)₃·H₂O (Ln3+∶Gd3+ or Nd3+)-doped silica gel, the addition of Gd3+ increased the luminescence efficiency of Tb3+, while the luminescence of Tb3+ was quenched remarkably with the addition of Nd3+. Possible mechanism behind the co-luminescence phenomena of lanthanide complexes-doped silica gels is discussed.