离子液体参与构建的液体—液晶界面型传感器的研究

发布时间：2018-05-22 08:43

本文选题：液体-液晶界面型传感器 + 离子液体　；参考：《曲阜师范大学》2017年硕士论文

【摘要】：液体-液晶界面型传感器通常利用表面活性剂分子与目标物在液体-液晶界面上发生相互作用进而诱导液晶分子的排列取向发生变化,从而实现对目标物的检测。它具有操作更简便、可实时检测生物或者化学反应的进程、更易于构建阵列化和微型化的传感器等优势,因此受到了广泛的关注。但是目前,这类传感器的相关研究大都局限于以水作为介质、以传统的表面活性剂作为修饰剂,难以满足对目标物及生化事件检测的越来越高的要求。因此,亟需寻找合适的非水溶剂以及设计开发结构新颖的表面活性剂,用以构建新型的液体-液晶界面传感器。鉴于此,本论文着眼于以绿色溶剂—离子液体作为介质;同时设计合成各种结构的表面活性剂(如刺激响应性表面活性剂、表面活性离子液体和Gemini表面活性剂等),以之修饰液体-液晶界面,进而构建新型液体-液晶界面传感器。具体说来,本论文的主要内容包括以下四个部分:第一章介绍了液晶界面型传感器、表面活性剂和离子液体等方面的相关背景知识以及国内外相关的研究现状,并提出了本论文的研究思路。第二章合成了光响应的偶氮苯类表面活性剂—4-乙基偶氮苯-4'-己氧基三甲基溴化铵(azoTAB),并用其作为修饰剂,以离子液体—硝酸乙铵(EAN)为介质,构建了稳定持久可逆的液体-液晶光响应型界面。本章主要采用了偏光显微镜、紫外/可见/近红外分光光度计等技术手段进行实验研究。研究发现,当azoTAB的浓度较高时,在紫外光和可见光的交替作用下,液晶的光学形貌和液晶分子在液-液界面上的排列方式分别发生了由暗到亮及由垂直到平行的交替变化。这主要是由于偶氮苯类表面活性剂分子的构型经历了顺反异构的可逆变化。研究发现,相比于水-液晶界面,EAN几乎不蒸发的特性使得液晶的光学图片更加稳定,至少可在一个月内不用更换溶剂,并可实现多次光控可逆循环,因此离子液体-液晶界面具有更好的可控性、稳定性和重现性。另外,将少量EAN作为电解质添加到水溶液-液晶界面上,得到了与添加无机盐电解质(例如NaCl)类似的结果,即导致液晶光学形貌变化的临界浓度降低,主要原因是电解质屏蔽了表面活性剂头基之间的静电斥力;但当加入大量的EAN时改变了溶剂性质,致使临界浓度增大。第三章研究了一系列结构不同的咪唑类表面活性离子液体分别修饰水溶液-液晶界面和离子液体-液晶界面时对液晶分子排列取向的影响。本章合成了三种短链的离子液体—硝酸乙铵(EAN)、硝酸丙铵(PAN)、硝酸丁铵(BAN)和八种咪唑类表面活性离子液体(IM-SAILs),包括单链IM-SAILs:1-十二烷基-3-甲基咪唑溴([C12mim]Br)、1-十四烷基-3-甲基咪唑溴([C14mim]Br)、1-十六烷基-3-甲基咪唑溴([C16mim]Br)、1-十二烷基-3-甲基咪唑水杨酸盐([C12mim]Sal)、1-十二烷基-3-甲基咪唑3-羟基-2-萘酸盐([C12mim]HNC)、1-十二烷基-3-甲基咪唑肉桂酸盐([C12mim]CA)和1-十二烷基-3-甲基咪唑对羟基肉桂酸盐([C12mim]PCA)以及双子IM-SAIL:二亚甲基-1,2-双(3-十二烷基咪唑)溴([C12-2-C12im]Br2)。主要采用偏光显微镜观察了烷基链长、链数及反离子不同的IM-SAILs对液晶偏光响应的影响。发现无论是在水溶液-液晶界面还是EAN-液晶界面,随着[Cnmim]Br(n=12-16)烷基链的增长,使临界浓度逐渐减小;双烷基链[C12-2-C12im]Br2的临界浓度明显低于单链[C12mim]Br;反离子的不同(Br-和各种芳香阴离子)却对液晶分子在界面上的排列取向影响很小。另外,相比于水溶液-液晶界面,离子液体(EAN、PAN或BAN)-液晶界面拥有更高的临界浓度和更稳定的液晶光学形貌,这主要归因于溶剂内部结构的差异。第四章主要采用偏光显微镜研究了两类结构不同的阳离子型Gemini表面活性剂修饰到液体-液晶界面时引起液晶排列取向的变化情况。设计合成了季铵盐型的Gemini表面活性剂:溴化二亚甲基-1,2-双烷基季铵盐(m-2-n,m=12,14,16;n=12,10,8;m+n=24)以及咪唑类Gemini表面活性离子液体:二亚甲基-1,2-双(3-烷基咪唑)溴([Cn-s-Cnim]Br2,s=2,n=6,8,10,12,16)和s亚甲基-1,s-双(3-十二烷基咪唑)溴([Cn-s-Cnim]Br2,n=12,s=2,4,6,10)。研究发现,咪唑类Gemini表面活性离子液体的双烷基链越长,诱导临界浓度越低。随着咪唑类Gemini表面活性离子液体连接基的增长,其临界浓度也随之增大。对称性不同、但双烷基链长总和相等的三种季铵盐型的Gemini表面活性剂具有相近的临界浓度。以咪唑为头基的[C12-2-C12im]Br2的临界浓度比季铵阳离子为头基的12-2-12明显低。说明对Gemini表面活性剂来说,双烷基链总链长、连接基长度以及头基类型的改变都会诱导液晶分子在液体-液晶界面上的排列取向发生变化。以上研究工作表明,离子液体和新型表面活性剂在液体-液晶传感器领域中具有很好的应用前景。本论文为拓宽液体-液晶界面传感器的构建方法以及提升其检测性能奠定了坚实的理论基础。
[Abstract]:Liquid liquid crystal interface sensor usually uses the interaction of surfactant molecules and objects on liquid crystal interface and then induces the alignment of liquid crystal molecules to change the alignment of liquid crystal molecules, thus realizing the detection of the target. It is easier to operate, can detect the process of biological or chemical reaction in real time, and is easier to build the array. However, most of the related research of this kind of sensor is limited to water as the medium and the traditional surface active agent as a modifier, so it is difficult to meet the higher requirements for the detection of targets and biochemical events. Therefore, it is urgent to find a suitable non water soluble solution. The agent and the design and development of a novel surface active agent are used to construct a new liquid liquid crystal interface sensor. In view of this, this paper focuses on the use of green solvents, ionic liquids as medium, and the design of synthetic surfactants (such as irritation surfactants, surface active ionic liquids and Gemini surface activity). The main contents of this paper include the following four parts: the first chapter introduces the related background knowledge of the liquid crystal interface sensor, the surface active agent and the ionic liquid, as well as the related research status at home and abroad, and proposes the relevant research status at home and abroad. The second chapter synthesizes the photoresponse azobenzene surface active agent, 4- ethyl azobenzene -4'- dioxy ammonium bromide (azoTAB), and uses it as a modifier, and uses the ionic liquid - ammonium nitrate (EAN) as the medium to build a stable and durable liquid liquid crystal light response interface. This chapter is mainly used in this chapter. It is found that the optical morphology of the liquid crystal and the arrangement of liquid crystal molecules on the liquid liquid interface occur from dark to bright and from perpendicular to parallel to the liquid liquid interface, when the concentration of azoTAB is high, and when the concentration of ultraviolet and visible light is high. It is mainly because the configuration of azobenzene surfactant molecules has undergone a reversible change in the CIS and trans isomerization. It is found that the properties of EAN almost do not evaporate in comparison with the water liquid crystal interface, which makes the optical images of the liquid crystal more stable, at least one month without replacing the solvent, and thus can achieve multiple optical control reversible cycles. The ionic liquid - liquid crystal interface has better controllability, stability and reproducibility. In addition, a small amount of EAN as an electrolyte is added to the liquid liquid crystal interface. The result is similar to the addition of inorganic salt electrolytes (such as NaCl), that is, the critical concentration of the changes in the optical morphology of the liquid crystal is reduced, mainly because the electrolyte shields the surface. The electrostatic repulsion between the active agent head groups; but when a large amount of EAN is added, the solvent properties are changed and the critical concentration increases. The third chapter studies the influence of a series of imidazole surface active ionic liquids on the alignment of liquid crystal molecules with liquid crystal interface and ionic liquid liquid crystal interface. Three kinds of short chain ionic liquids - ammonium nitrate (EAN), ammonium nitrate (PAN), ammonium nitrate (BAN) and eight imidazole surface active ionic liquids (IM-SAILs), including single chain IM-SAILs:1- twelve alkyl -3- methyl imidazolium bromide ([C12mim]Br), 1- fourteen alkyl -3- methyl imidazolium bromide ([C14mim]Br), 1- sixteen alkyl -3- methyl imidazolium bromide (1), 1 - twelve alkyl -3- methidazolicsalicylate ([C12mim]Sal), 1- twelve alkyl -3- methyl imidazole 3- hydroxyl -2- naphthalate ([C12mim]HNC), 1- twelve alkyl -3- methyl imidazole cinnamate ([C12mim]CA) and 1- twelve alkyl -3- methylimidazole against hydroxyl cinnamate, and Gemini two methylene glycol (twelve alkyl imidazole) Bromine ([C12-2-C12im]Br2). The effect of alkyl chain length, chain number and different IM-SAILs on the response of liquid crystal polarization is observed mainly by polarizing microscope. It is found that the critical concentration gradually decreases with the increase of [Cnmim]Br (n=12-16) alkyl chain in aqueous solution liquid crystal interface or EAN- liquid crystal interface; the dialkyl chain [C12-2-C12im]Br2 is gradually reduced. The critical concentration is obviously lower than the single strand [C12mim]Br, but the difference of the reverse ion (Br- and various aromatic anions) has little influence on the arrangement orientation of the liquid crystal molecules on the interface. In addition, the ionic liquid (EAN, PAN or BAN) - liquid crystal interface has higher critical concentration and a more stable liquid crystal optical morphology than the aqueous liquid crystal interface. In the fourth chapter, the fourth chapter mainly uses polarizing microscope to study the changes in the alignment of liquid crystals when the two kinds of cationic surfactant of different structures are modified to liquid crystal interface. A quaternary ammonium salt Gemini surfactant is designed and synthesized, and two methylene -1,2- dialkyl quaternary ammonium bromide is prepared. Salt (m-2-n, m=12,14,16; n=12,10,8; m+n=24) and imidazole Gemini surface active ionic liquids: two methylene -1,2- double (3- alkyl imidazole) bromine ([Cn-s-Cnim]Br2, s=2, n=6,8,10,12,16) and s methylene -1. The longer the base chain is, the lower the critical concentration is. With the increase of the imidazole Gemini surface active ionic liquid junction, the critical concentration also increases. The symmetry is different, but the three quaternary ammonium salt type Gemini surfactants with equal dialkyl chain length have similar critical concentration. The critical [C12-2-C12im]Br2 critical to imidazole is critical. The concentration ratio of quaternary ammonium cation to the head based 12-2-12 is significantly lower. It shows that the total chain length of the alkyl chain, the length of the connective group and the change of the head type will induce the changes in the alignment of the liquid crystal molecules at the liquid crystal interface for the Gemini surfactants. The above research shows that the ionic liquid and the new surfactant are in the liquid. It has a good application prospect in the field of liquid crystal sensor. This paper lays a solid theoretical foundation for widening the method of constructing liquid crystal interface sensor and improving its detection performance.
【学位授予单位】：曲阜师范大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O645.1;TP212

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