[C_4mim][PF_6]和[C_4mim][NTf_2]离子液体辐射诱导的相行为及荧光行为变化

离子液体因其低挥发性,高热稳定性及优良的萃取性能被认为是萃取分离放射性核素的新一代绿色溶剂,而研究离子液体本身的辐射效应是其实际应用的重要前提.本文以~(60)Co为辐射源,系统研究了γ辐照对两种常见的憎水性咪唑离子液体1-丁基-3-甲基咪唑六氟磷酸盐(C_4mim]PF_6])和1-丁基-3-甲基咪唑三氟甲基磺酰胺酸盐(C_4mim]NTf_2])的相行为及荧光行为的影响.在相行为方面,γ辐照使离子液体的结晶驰豫时间增加,导致其低温结晶延迟.在荧光行为方面,γ辐照后离子液体的荧光光谱保持原有的"红边效应(red edge effect)",但随吸收剂量增加,光谱整体发生红移(最大移动幅度达150 nm).并且这种"红边效应"在辐照后离子液体的乙腈稀释剂中仍然存在,且随稀释倍数增加光谱整体发生蓝移.C_4mim]PF_6]和C_4mim]NTf_2]离子液体辐照后的这种相行为及荧光行为的变化可归因于辐照对其阴阳离子空间相关性(缔合行为)的影响.

Radiation-Induced Changes of Phase Behavior and Fluorescence Properties of the Ionic Liquids [C_4mim][PF_6] and [C_4mim][NTf_2]

The application of room-temperature ionic liquids(RTILs)to the separation of high level radioactive nuclides from waste water demands a comprehensive knowledge of the radiation effects on the RTILs.Herein,we report a systematic study on the influence of γ-irradiation on the phase behavior and fluorescence properties of the widely used hydrophobic room-temperature ionic liquidsC_4mim]X,whereC_4mim]~+is 1-butyl-3-methylimidazolium and X~-is hexafluorophosphate(PF~-_6)and bis(trifluoromethylsulfonyl)imide(NTf~-_2),respectively.It was found that the relaxation time of crystallization in the ILs increased during γ-irradiation leading to a delay before crystallization.The irradiated ILs showed an obvious"red edge effect"similar to that in unirradiated ILs.The whole spectrum,however,shifted to a longer wavelength with increasing the dose and the maximum variation was ca 150 nm.Furthermore,the "red edge effect"was unexpectedly observed in an acetonitrile solution of irradiated ILs and the whole spectrum shifted towards a shorter wavelength with increasing the dilution.All the above-mentioned observations relating to the phase behavior and fluorescence properties are attributed to a change in the spatial correlation between cations and anions in the ILs after γ-irradiation.