Microheterogeneity of some imidazolium ionic liquids as revealed by fluorescence correlation spectroscopy and lifetime studies.
Microheterogeneity of some imidazolium ionic liquids as revealed by fluorescence correlation spectroscopy and lifetime studies.
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DOI：
10.1021/jp3061202
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发表时间：
2012-10
期刊：
影响因子：
--
通讯作者：
S. Patra;A. Samanta
中科院分区：
文献类型：
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作者：
S. Patra;A. Samanta
室温离子液体（RTILs）的微观结构和动力学是这类溶剂的一些特殊性质的原因，它继续引起研究人员的兴趣，并激发了新的研究。在此，我们使用荧光相关光谱（FCS）技术研究了一些探针分子在RTILs中的扩散，其结果与荧光寿命研究结果相结合，为这类新型溶剂的微观结构细节提供了见解。在五种精心选择的1-烷基-3-甲基咪唑离子液体中使用三种带电和中性探针分子进行的实验表明，与传统溶剂不同，这些探针在RTILs中表现出双峰扩散行为，从而表明存在两种不同的环境。随着阳离子烷基链长度的增加，扩散的慢速组分的贡献增大。这些结果不仅得到了系统荧光强度的双指数衰减行为的支持，而且寿命成分的单个值及其权重允许确定两种主要环境的性质。从本质上讲，这些结果指出了两种结合技术在揭示离子液体的一些复杂特征方面的潜力。
The microscopic structure and dynamics of the room temperature ionic liquids (RTILs) that are responsible for some of the peculiar properties of this class of solvents continue to intrigue the researchers and stimulate new investigations. Herein, we use the fluorescence correlation spectroscopy (FCS) technique to study the diffusion of some probe molecules in RTILs, the results of which, when combined with those obtained from fluorescence lifetime studies, provide insights into the microscopic structural details of this class of novel solvents. Experiments performed with three charged and neutral probe molecules in five carefully selected 1-alkyl-3-methylimidazolium ionic liquids reveal that unlike in conventional solvents these probes exhibit a bimodal diffusion behavior in RTILs thus indicating the presence of two distinct environments. It is found that the contribution of the slow component of the diffusion increases with increasing alkyl chain length of the cation. Not only are these results supported by the biexponential decay behavior of the fluorescence intensity of the systems, but the individual values of the lifetime components and their weight allow determination of the nature of the two major environments. In essence, the results point to the potential of the two combined techniques in unraveling some of the complex features of the ionic liquids.