【作者】 刘杰；

【导师】 于丽；

【作者基本信息】 山东大学 ， 化学工程（专业学位）， 2021， 硕士

【摘要】 环境污染给生态系统和人类社会造成了直接和间接的危害,影响人类生活质量和身心健康,严重的环境污染甚至还会造成重大社会问题。目前常见的环境污染物检测方法(如电化学法、荧光法和色谱法等)存在设备昂贵、操作复杂和不易携带等问题。因此开发简单、便携、低成本的可视化污染物检测平台具有重要意义。液晶材料,由于具有长程有序性、优良的双折射性及对表面敏感性等性质被应用于分析检测领域中,为发展便捷可视化的环境污染物检测策略提供了有力的材料支撑。本论文主要利用向列相液晶(Nematic liquid crystal,NLC)4-氰基-4’-戊基联苯(5CB)和胆甾相液晶(Cholesteric liquid crystal,CLC)作为信号识别元件,将生物或化学信号转变为肉眼可见的光学信号,从而达到对环境污染物可视化检测的目的。论文内容主要包括以下四个部分:第一章介绍了环境污染物的分类及危害、NLC传感平台和CLC光子晶体传感器的构筑及机理等方面的相关背景知识,并综述了近年来NLC传感平台和CLC光子晶体在分析检测领域中的国内外研究现状,在此基础上提出了本论文的研究思路。第二章利用Pb2+对DNAzyme的特异性识别作用引发的磁珠表面原位滚环扩增(Rolling circle amplification,RCA)反应,并与NLC传感平台相结合,提出了一种高灵敏度、高特异性检测Pb2+的方法。首先,将链霉素亲和素包覆的磁珠与生物素化DNAzyme相连接,当目标物Pb2+存在的时候,可以引发磁珠表面的原位RCA反应,得到一段长的单链DNA(Single strand DNA,ssDNA)。ssDNA能够破坏NLC界面上的十八烷基三甲基溴化铵(OTAB)单层膜,使5CB分子呈现平行或倾斜排列,在偏光显微镜下得到明亮的光学图像。然而,当Pb2+不存在时,不会引发RCA反应,此时5CB分子保持垂直的排列取向,对应于暗的NLC光学形貌。据此,可以通过观察NLC光学形貌的亮暗变化来实现检测水中的Pb2+,其检测限可达16.7pM。这种方法在检测大明湖水及自来水中的Pb2+时也表现出了优良的性能。由于该策略避免了实际水样中杂质对NLC传感平台的干扰,为污水中其它重金属离子的检测也提供了新思路,对于环境水污染的监测和治理具有重要意义。第三章基于毛细管中高氯酸铜(Cu(ClO4)2)掺杂的NLC液滴构筑了检测甲基磷酸二甲酯(Dimethyl methyl phosphate,DMMP)气体的传感平台,成功实现了对DMMP气体的快速、高灵敏度检测。掺杂了Cu(ClO4)2的NLC液滴原本呈现暗的光学形貌;通入DMMP气体之后,由于它与Cu(C104)2之间具有更强的相互作用力,会干扰Cu(C104)2对NLC分子的锚定,此时得到明亮的扇形形貌,因此通过观察NLC液滴光学形貌的亮暗变化,实现对DMMP气体的检测,其检测限为2.0 ppb。此外,该NLC液滴传感平台在重复使用12次或者在室温下存放两周之后,都仍然对DMMP气体保持良好的传感性能,表明该NLC传感平台具有可重复使用性及良好的稳定性。本章以毛细管为衬底,构筑了小型化、便携式、可重复使用的高灵敏度NLC液滴微阵列,成功实现了对DMMP气体的可视化检测,该策略在有机磷神经毒剂的检测方面具有很大的应用潜力。第四章通过将脲酶固定在具有pH响应性的胆甾相液晶聚丙烯酸(Cholesteric liquid crystal and polyacrylic acid,CLC-PAA)光子晶体凝胶膜上,利用 Hg2+对脲酶活性的抑制作用,从而构筑了一种制备简单、价格低廉、无需标记的检测Hg2+的可视化传感方法。当不存在Hg2+时,脲酶水解尿素产生NH3,导致CLC-PAA光子晶体凝胶膜内部微环境的pH增加,引发该薄膜的颜色发生从绿色到橙黄色的显著变化,薄膜的反射光波长发生明显红移。Hg2+的存在能够抑制脲酶的活性,使得薄膜的颜色变化不明显,对应于反射光波长的变化也较小。因此可以通过测定薄膜的反射光波长的位移变化实现对Hg2+的定量检测。该传感器的检测限约为10 nM。该方法在环境水资源重金属离子的监测中具有良好的应用前景。更多还原

【Abstract】 Environmental pollutants cause direct and indirect harm to the ecosystem and human society,which can subsequently affect the quality of life,both physical and mental health of human beings.Serious environmental pollutants even trigger major social problems.At present,conventional methods for detecting environmental pollutants(e.g.electrochemical method,fluorescence method and chromatography,etc.)still have problems such as expensive instruments,complex operations and inconvenient to carry.Therefore,it is of great significance to develop a simple,portable,low-cost and visual detection strategy for environmental pollutants.Liquid crystals(LCs)with long-range order,excellent birefringence and surface sensitivity have been applied to the filed of analysis and detection,which provides a powerful material support for exploiting convenient and visualized new detection strategy for environmental pollutants.In this dissertation,biological or chemical signals were transformed into optical signals visible to the naked eye by using Nematic liquid crystal(NLC),namely 4-cyano-4’-pentylbiphenyl(5CB)and cholesteric liquid crystal(CLC)as signal recognition elements to achieve visual detection of environmental pollutants.There are four main parts in this dissertation as follows:Chapter 1 is an introduction of the relevant background knowledge of classification and hazards of environmental pollutants,NLCs sensing mechanism,construction of LCs platforms and CLC photonic crystal sensors,as well as the recent research status at home and abroad for NLCs sensing platform and CLC photonic crystal sensors in the fields of analysis and test.On this basis,the research ideas for this dissertation are put forward.In chapter 2,we construct a high sensitivity and specificity NLCs sensing platform for the detection of Pb2+ by the specific recognition effect of Pb2+ on DNAzyme and in-situ rolling circle amplification(RCA)on magnetic beads(MBs).Firstly,the MBs coated with streptomycin avidin were connected to the biotinylated DNAzyme.In the presence of the target Pb2+,the in-situ RCA reaction on the surface of the MBs was initiated to obtain a long single stranded DNA(ssDNA).The elongated ssDNA on the MBs disrupted the arrangement of self-assembled monolayers of octadecyl trimethyl ammonium bromide(OTAB),resulting in planar orientation of NLCs at the aqueous-LC interface.Thus,NLCs exhibited bright optical appearance.In contrast,in the absence of Pb2+,RCA on the MBs did not occur,in this case NLCs adopted perpendicular orientation and thus showed dark optical image.Therefore,variation in the bright and dark optical morphology of the NLCs can be employed as signals to detect Pb2+ in water.The detection limit of Pb2+ reaches as low as 16.7 pM.This method also shows excellent performance in detecting Pb2+ in tap water and lake water.Since this strategy avoids the interference of impurities in the actual water samples to the NLCs sensing platform,it also opens up a new path for the detection of other heavy metal ions in sewage,which has important implications for the monitoring and treatment of environmental water pollution.In chapter 3,we demonstrate a simple strategy for rapid and highly sensitive detection of dimethyl methyl phosphate(DMMP)gas by Cu(ClO4)2-doped 5CB droplets in the capillary.Originally,the NLCs droplets doped with Cu(ClO4)2 show presented a dark optical morphology.Then the optical response of the NLCs droplets changed from dark to bright appearance after adding DMMP to the capillary,due to the stronger interaction between DMMP and Cu(ClO4)2,which interfered with the anchoring of the LC molecules.Therefore,detection of DMMP gas can be realized by observing the dark-to-bright transformation in the optical morphology of NLCs droplets,and the detection limit reaches 2.0 ppb.In addition,the NLCs droplet sensing platform maintained good performance for the detection of DMMP gas even after 12 times of reuse or storage for two weeks at room temperature,indicating that it has good reusability and stability.In this chapter,a miniaturized,portable and reusable NLCs droplet microarray with high sensitivity was constructed on the capillary substrate,which successfully realized the visual detection of DMMP gas.This strategy has great application potential in the detection of organophosphorus nerve agents.In chapter 4,a simple preparation,low-cost and label-free pH-responsive cholesteric liquid crystal polyacrylic acid(CLC-PAA)photonic crystal hydrogel film immobilized with urease is developed for Hg2+ visual detection in which the activity of urease is inhibited by Hg2+.In the absence of Hg2+,urea was hydrolyzed by urease to produce NH3,which caused an increase in the pH of the microenvironment inside the CLC-PAA photonic crystal hydrogel film,leading to a significant change in the color from green to orange-yellow,and an obvious red shift in the reflected light wavelength for the film.The presence of Hg2+ could inhibit the activity of urease,so that the color variation of the film was not obvious,corresponding to a slight change of the reflected light wavelength.Therefore,Hg2+ can be quantitatively detected by measuring the position modification of the reflected light wavelength of the film.The limit detection of Hg2+ is about 10 nM.This method has a good application prospect in the monitoring of heavy metal ions in environmental water resources.更多还原