中文摘要：

1-烷基-3-甲基咪唑双三氟甲基磺酰胺型离子液体（[Cnmim][NTf2]）被认为是最有希望用于核燃料循环中的分离试剂之一,虽然其化学结构在辐照过程中变化不大,但在受到γ辐照后会发生明显的变色,因此有必要研究该类离子液体的变色原因.本文以60Co为辐照源,系统研究了辐照后不同C（1）-烷基链长和咪唑环上C（2）位上的H被甲基取代后离子液体的紫外-可见（UV-Vis）吸收光谱行为,并结合辐照后离子液体荧光光谱和质谱的变化,分析了导致该类离子液体辐照后颜色加深的原因.结果表明,随着咪唑环上C（1）―烷基链长度和剂量增大,离子液体颜色加深;而C（2）位上的H被甲基取代后颜色明显变浅.辐照后咪唑型离子液体的变色主要来自于辐照后产生的烷基侧链含双键的咪唑阳离子,咪唑阳离子二聚体和含氟咪唑化合物.此外,γ辐照引起咪唑阳离子易发生π-π堆积,而聚集态含量增加也会引起颜色加深.

英文摘要：

Ionic liquids 1-alkyl-3-methylbis（trifluoromethylsulfonyl）imide （[C n mim] [NTf2 ]） are promising separating reagents in the nuclear fuel cycle.Their chemical structure changes slightly when exposed to γ radiation,but the apparent darkening of [Cn mim][NTf 2 ] occurs at low dose.This radiation-induced darkening of [Cn mim][NTf2 ] should be investigated further.To understand the effect of radiation on [C n mim][NTf2 ],we systematically studied the influences of the length of the C（1）―alkyl chain and substitution of C（2）―H on the UV-Vis spectra of irradiated [C n mim][NTf2 ].Fluorescence and mass spectra of [C n mim][NTf2 ] allowed the possible colored products to be determined.The darkening of [C n mim][NTf2 ] is more obvious as the length of the C（1）―alkyl chain and absorbed dose increase,but it is weakened effectively after methylation at the C（2）-position of the imidazole ring.The dominant colored products are possibly imidazolium cations containing double bonds,dimers of imidazolium cations and fluorinated imidazolium compounds.Imidazolium cations could aggregate through π-π stacking after γ-irradiation,and the associated states may also play a role in darkening these ionic liquids.