基于双官能团荧光增敏离子液体的“无有机溶剂微萃取”及其分析应用研究

Currently, the microextraction technique based on functionalized ionic liquids is a main focus in the field of green chemistry. However, the previous researches were mainly involved in single-functionalized ionic liquids, while less in difunctionalized ones. In the follow-up study of our previous NSFC (21077079), we found that when –SH and –TA (trimesic acid) were introduced as cation and anion, respectively, in the imidazolium ring, the synthesized difunctionalized ionic liquids had strongly synergistic fluorescence-enhancing effects on phenolic estrogens (PEs). So far, no systematic study has been conducted on their interaction between difunctionalized ionic liquids and fluorescent molecules. This proposal aims to elucidate the mechanisms on the synergistic fluorescence-enhancing effects of difunctionalized ionic liquids on PEs and their analytical application by means of the following researches: (1) A series of novel difunctionalized ionic liquids with –SH and –TA will be synthesized by means of four-step synthetic methods; (2) A series of theories were used to illustrate the strongly fluorescence-enhancing mechanisms of this novel ionic liquids: TICT fluorescent probe, energy distribution effect, special solvent effect theories and so on; (3) The “no-organic solvent microextraction” technique is developed by means of the water-insoluble difunctionalized ionic liquids as extraction solvent and water-soluble ones as dispersive solvent. The water-soluble differences in difunctionalized ionic liquids result from the differences in the length of alkyl chains. After the above pretreatment, it aims to realize the high enrichment efficiency and sensitize fluorescence determination for PEs at trace levels. This study can lay theoretical foundation for developing novel ionic liquids possessing strongly fluorescence-enhancing effects, and further promote wide application of ionic liquids in environmental analytical fields.

基于功能化离子液体的微萃取技术是目前绿色化学领域的研究热点。然而已有研究多为单离子功能化，较少涉及双官能团功能化。申请人在已结题基金的拓展研究中发现：在咪唑类离子液体上引入均酸和巯基，合成的双官能团离子液体对酚类雌激素（PEs）具协同强荧光增敏效应，但目前对双官能团离子液体与荧光分子之间的相互作用及其应用缺乏系统地探讨。鉴于此，本项目采用四步合成法进行系列巯基均酸类双官能团离子液体的合成；以典型TICT荧光探针为手段，利用TICT、能级分布和离子液体特殊溶剂效应等理论综合解析该类离子液体对PEs所产生的强荧光增敏机理；筛选具更强增敏效应的种类，利用不同链长所导致的溶解性差异，构建基于萃取剂和分散剂均使用同类功能化离子液体的“无有机溶剂微萃取”技术，实现痕量PEs的高效富集和灵敏荧光检测。该研究能为今后研发离子液体强荧光增敏剂提供前期理论基础，并将进一步推进离子液体在环境分析领域的广泛应用。

双官能团离子液体对有机污染物产生的荧光增敏效应，不仅涉及到阳离子和阴离子官能团各自的效应，还涉及到其母体结构及微环境效应等因素对化合物所产生的综合效应，因此该类离子液体对化合物所产生的综合荧光效应机理非常复杂。本课题针对前期研发的巯基功能化离子液体的荧光效应及其应用开展了系列研究，取得结果如下：（1）开发了系列不同烷基长度和阴离子的巯基功能化离子液体，并对它们的结构进行了系统表征。（2）分析了不同种类[HS-CnMIM]Y的荧光强度。该类离子液体由于结构上产生了n-π*效应，故具有强荧光效应，显示出比常规离子液体高达上百倍的分子荧光。（3）开发了基于超薄g-C3N4 (CNNS) 的“ON-OFF-ON”传感平台，用于顺序检测Ag+和[HS-BMIM]Br。巯基化离子液体与Ag+之间的反应导致CNNS表面上的官能团活化，故能够恢复猝灭的荧光。构建的“ON-OFF-ON”纳米荧光传感器，对于[HS-BMIM]Br检测限为4.28 nM。（4）制备了巯基化离子液体[HS-C4MIM]Br和双阳性离子液体[Cn(MIM)2]Br2，以其作为分散剂和pH调节剂，通过结合常规萃取剂，开发了基于巯基咪唑盐的“全离子液体微萃取”用于测定食品和环境水样中的双酚类化合物，检出限为0.13-0.82 μg L-1，回收率为91.6-107.9%。该技术具有如下优势：（Ⅰ）既可作为分散剂，又可作为pH调节剂，简化了实验步骤；（Ⅱ）能够产生明显的分层现象，方便了分离。（5）开发了基于双功能溶剂的盐析增强型离子液体微萃取方法，用于检测食品和环境水样中宽极性的药物和酚类污染物（log Kow= -1.32~5.40）。该方法能同时检测极性较宽范围的痕量污染物，减少了环境和食品检测的工作量，故在分析领域具有较大的应用潜力。这些结果共发表SCI论文13篇，获批专利1项，新申请专利5项。