【作者】 何刚；

【导师】 房喻；

【作者基本信息】 陕西师范大学 ， 材料学， 2011， 博士

【摘要】 近年来,随着反恐、反化学生物武器、非金属地雷探测、环境质量监测等需求的增加,世界各国对各类高性能薄膜传感器的研究愈来愈重视。相对于均相(溶液)传感器,薄膜传感器具有可重复使用、基本不污染待测体系、易于器件化等优点,因此,备受人们重视。而共轭聚合物作为一种新的传感元素因以下原因受到特别的关注：(1)摩尔消光系数可达106M-1cm-1,具有很强的集光能力；(2)因整个分子主链为共轭结构,允许光激发电子在链上迅速流动,具有所谓的“分子导线效应”(Molecular Wire Effect),对被测量分子表现为“一点接触、多点响应”,呈现出显著的信号放大效应；(3)共轭荧光聚合物的光诱导电子转移或者能量转移是一个超快过程,一般可在数百飞秒内完成,较之正常的辐射衰变快4个数量级,因此与猝灭剂作用时,可表现为“超级猝灭”(Super-Quenching)。就目前的研究现状而言,基于共轭聚合物的薄膜传感器已经表现出巨大的优势和广阔的应用前景。然而需要指出的是,就硝基芳烃类爆炸物检测而言,到目前为止大多数工作集中在通过聚合物结构改造或者设计制备新的共轭聚合物来提高这类材料的传感性能。事实上,这并不是提高荧光传感器检测性能的唯一方法。通过对荧光薄膜传感器制备方法的改进,也可以提高传感器对硝基芳烃类爆炸物的检测性能。本论文在硝基芳烃类爆炸物检测用聚合物传感器研究综述的基础上,结合本实验室在硝基芳烃类爆炸物检测方面的研究进展,利用超分子化学原理,探索了薄膜制备方式对薄膜传感器性能的影响,以共轭荧光聚合物为传感元素,设计、制备了多种对硝基芳烃类爆炸物,特别是对某种特定爆炸物具有高灵敏度和选择性的荧光传感薄膜。同时,作为主要成员参与了以本实验开发的高性能薄膜传感器为核心部件的便携式爆炸物探测仪的研发和应用推广工作。具体来讲,主要完成了以下工作：(1)将六苯基环戊二烯硅烷的纳米颗粒作为传感元素掺杂于壳聚糖,通过旋涂技术将其固定于基质表面,得到了一种新型的荧光薄膜。对其传感性能的研究发现,此薄膜可以对苦味酸实现高灵敏度、高选择性的检测,检出限达到2.1×10-8mol/L。并且三硝基甲苯(TNT)、二硝基甲苯(DNT)、硝基苯(NB)、苯酚、苯、甲苯、乙醇、甲醇和硝酸锌的引入对传感薄膜的荧光发射影响很小。传感机理研究发现,苦味酸阴离子与壳聚糖表面胺基阳离子之间的静电相互作用是此薄膜高选择性和高灵敏度的主要原因。同时,壳聚糖的网络结构还有助于六苯基环戊二烯硅烷纳米粒子的稳定,阻止了其进一步的聚集。此外,此薄膜对于苦味酸的检测完全可逆。由于该薄膜制备工艺简单,传感性能优异,有望在实践中获得应用。(2)设计、合成了两种含芘的苯乙炔类共轭聚合物(PyPE-1和PyPE-2)。将这两种聚合物分别旋涂到玻璃基质上制备得薄膜1和薄膜2,并对其传感行为进行了研究。结果表明,在水相中,这两种薄膜对2,4,6-三硝基甲苯(TNT)的存在都非常敏感。相对于不含芘的类似物聚苯乙炔撑(PPE)所制备的薄膜3,薄膜1和2对于水相中TNT的检测不仅具有更高的灵敏度,而且还表现出了较好的选择性。这主要归结为两个原因：第一,芘的引入增强了聚合物和TNT之间的π-π相互作用：第二,芘的引入使得聚合物与TNT分子轨道能量更加匹配。进一步的研究表明,薄膜1对TNT的传感过程是可逆的。荧光寿命的测定表明该荧光猝灭过程是一种静态猝灭。该薄膜性能优越、制备简单,有望发展成为对地下水和海水中TNT具有高灵敏和高选择性的传感器。(3)首次提出了将单分子层化学的优点与共轭聚合物检测时所具有的信号放大效应相结合来制备荧光传感薄膜。在此思想的指导下,将寡聚二苯基硅烷化学键合于玻璃基质表面,制备了一种性能优越的气相硝基芳烃类爆炸物检测用荧光传感薄膜。正是兼具两者的优势,所制备的薄膜实现了对于气相中微痕量的硝基芳烃类爆炸物超灵敏、高选择性检测。同时,此薄膜可多次、重复使用。荧光寿命的测定结果表明,TNT对传感薄膜的猝灭过程为静态猝灭。由于该薄膜对硝基芳烃类爆炸物的超灵敏响应、高选择性和可逆性使得其极有希望发展成为一类对硝基芳烃类爆炸物敏感的荧光薄膜传感器。(4)将聚苯乙炔撑衍生物(M-PPEs)化学键合于玻璃基质表面,制备了一种荧光行为可控的共轭荧光聚合物荧光薄膜。研究发现,薄膜的荧光行为对其所处的介质极性极为敏感。这主要是由于不同极性溶剂中,固定化于基质表面的聚合物长而柔性的烷基侧链构象会发生变化,从而导致了聚合物主链相互作用的改变。在“不良”溶剂或者其蒸气中,侧链以压缩构象存在,导致聚合物主链之间聚集,使得薄膜的荧光强度降低,表现出明显的聚集荧光猝灭现象。然而在“良”溶剂或者其蒸气中,侧链趋向于伸展状态,采取一种松散的或者伸展的线圈构象,有效阻止聚合物之间的聚集,因此薄膜的荧光强度增强。有意思的是,这种聚集一解聚集的过程完全可逆,而且可在一分钟以内达到平衡。静态和时间分辨荧光技术及分子动力学模拟的研究都证明了聚合物侧链是薄膜能够接受外界刺激响应的决定性因素。另外,基于此薄膜丰富的荧光行为,发展了两种两输入的INH和OR逻辑门。毫无疑问,利用聚合物侧链构象的改变来实现薄膜荧光行为的调控将是设计基于共轭聚合物单分子层荧光传感薄膜一种新的策略,不仅会大大拓展基于共轭聚合物荧光薄膜的设计思路,也必为此类薄膜的器件化奠定坚实的基础。(5)将强络合能力的喹啉基团引入共轭聚合物的设计、合成中来,制备了三种含8-羟基喹啉的共轭聚合物(P1,P2和P3)。由于聚合物络合位点的差异,聚合物对铜离子的响应有比较大的差异。含有羟基和咪唑的聚合物P2和P3对铜离子表现出了较好的响应,聚合物的荧光被有效的猝灭。而P1对铜离子几乎不响应。更为有趣的是,P2与铜离子的相互作用是可逆的。加入与铜离子相互作用更强的氨基酸,会使铜离子与聚合物远离,P2的荧光恢复。而由于P3与铜离子相互作用太强,氨基酸,甚至EDTA都不能使荧光恢复。利用这一现象,可以实现对溶液中氨基酸的灵敏检测。(6)高灵敏、便携式硝基芳烃类爆炸物探测仪由于其特殊的应用价值已经成为此类研究工作发展趋势之一。在本论文的附录工作中,以第二、三部分制备的传感薄膜为核心器件,作为主要成员参与设计并加工出硝基芳烃类爆炸物检测用便携式探测仪。重点介绍了仪器相关的器件、电路、及相应的检测性能。毋庸置疑,高灵敏、便携式硝基芳烃类爆炸物探测仪的成功研发必将在环境污染监测、反恐等领域发挥重要的作用。本论文的创新点在于：(1)改进了传统荧光薄膜的制备方法,发现了基质组成和结构对薄膜检测性能的重要作用,为同类薄膜的设计制备提供了新的思路。(2)设计、制备了多种新型共轭荧光聚合物,得到了综合性能优异,在旋涂成膜条件下对硝基芳烃类爆炸物高度敏感的传感薄膜材料。(3)首次提出将单分子层化学组装与共轭荧光聚合物结合创制液、气两相通用高性能荧光敏感薄膜的思路,由此制备了一系列可对硝基芳烃类爆炸物超灵敏、高选择性检测的传感薄膜。与此同时,发现在不改变基质类型和传感元素主体结构的条件下,仅仅通过改变聚合物侧链结构就可以得到性能完全不同的荧光薄膜材料,极大地拓展了此类薄膜的创新空间。(4)基于实验室创制的传感薄膜,参与设计并加工出了高灵敏、便携式硝基芳烃类爆炸物探测仪,目前,其市场化的工作也正在进行中。更多还原

【Abstract】 The design and fabrication of chemical sensors with high sensitivity and selectivity has attracted extensive attention for several decades since they play a great role in environmental monitoring, medical diagnosis, forensic analysis, especially in anti-terrorism. Film sensors offer advantages in terms of reversibility and reproducibility, which are the two crucial parameters for practical applications of fluorescent sensors and their actual device implementation. As a novel kind of sensing element, conjugated polymers (CPs) have recently emerged as one important family of sensing units and are used extensively in chemical sensors. CPs provide several advantageous features:1) high molar extinction coefficient (106 M-1 cm-1),2) the backbone of CPs enabling the rapid propagation of an exciton throughout the individual polymer chain, which is the so-called "molecular wire effect",3) super-fast photo induced electron transfer or energy transfer between CPs and analytes (in several hundred femtoseconds), which leads to "super-quenching effect". More recently, most of the scientists have paid their attention to developing sensing materials, such as design and synthesis of novel CPs. The results showed that this strategy can greatly enhance the sensing properties. However, this is not the only way to fabricate high performance film sensors. It was proven that the sensing performance of film sensor can also be improved through changing the preparation methods of film sensors.On the basis of the above discussion and the research progress in our lab, the objective of the present dissertation is to fabricate a series of CPs-based film sensors with novel sensing mechanisms. After a brief review on polymer sensors for nitro-aromatic explosive detection (the first Chapter), the design strategies and fabrication of several CPs-based film sensors and their sensing abilities were described in the following chapters (Chapter 2 to 6). These film sensors were proved to be highly sensitive and selective to the target analytes, such as nitro-aromatic compounds and vapor of organic compounds. In addition, the related film sensor-based portable detector for nitro-aromatic explosives has been developed in our lab.In Chapter 3, a novel fluorescent film was fabricated by doping the aggregates of hexaphenylsilole (HPS) into a chitosan film. It was demonstrated that the fluorescence emission of the film is sensitive and highly selective to the presence of picric acid (PA). The detecting limit for PA is about 2.1×10-8 mol/L. Introduction of 2,4,6-trinitrotoluene (TNT),2,4-dinitrotoluene (DNT), nitrobenzene (NB), phenol, benzene, toluene, methanol, ethanol, and zinc nitrate (Zn(NO3)2) had little effect upon the fluorescence emission of the film. The selectivity of the film was attributed to the specific electrostatic association effect of the protonated substrate film to picrate anion and the screening effect of the film to the interferents. The network structure of the substrate film is also favorable for the stabilization of the fluorescence emission of the hybrid film through preventing the further aggregation of silole aggregates. Fluorescence lifetime measurements revealed that the quenching is static in nature. Furthermore, the quenching process is fully reversible. Considering the simplicity of the preparation and the outstanding performances of the hybrid film, it is expected that the film may be developed into a real-life PA sensor.In Chapter 4, two poly(pyrene-co-phenyleneethynylene)s of different compositions (PyPE-1 and PyPE-2) were synthesized and characterized. The two polymers had been casted onto glass plate surfaces to fabricate films (Film 1, Film 2) for investingating their sensing performances, separately. It has been demonstrated that the fluorescence emissions of the two films are sensitive to the presence of 2,4,6-trinitrotoluene (TNT) in aqueous phase. Interestingly, TNT shows little effect upon the emission of the parent polymer, poly(phenyleneethynylene) (PPE). The difference was explained by 1) theπ-πinteraction between pyrene moieties contained in the co-polymers and the analyte, TNT, molecules, and 2) more suitable matching of the LUMOs (lowest unoccupied molecular orbital) of the pyrene-containing conjugated polymers with that of TNT molecules. Further experiments demonstrated that the sensing is reversible, and rarely encounters interference from commonly found compounds, including other NACs. Fluorescence lifetime measurements revealed that the quenching is static in nature. The smart performance of the films and the easiness of their preparation guarantee that the films may be developed into sensor devices for super-sensitive detection of TNT in groundwater or seawater.In Chapter 5, the self-assembly monolayers (SAMs) techniques was used to fabricate sensing films. A fluorescent film sensor was prepared by chemical assembly of oligo(diphenylsilane)s on a glass plate surface, and was used for the detection of nitroaromatic compounds (NACs) in vapor phase. This design combines the advantages of fluorescent films based on single-layer chemistry and the signal amplification effect of conjugated polymers, and provides an effective way to create novel fluorescent sensing films for NACs explosives. The advantages have been demonstrated experimentally by the super sensitive response of the film mentioned above to the presence of trace amounts of NACs in vapor phase. Further experiments showed that the sensing process is reversible, and the common interferents have no interference to the process. Fluorescence lifetime measurement revealed that the quenching is static in nature. The super sensitive response, the reversibility and free interference of the sensing process make the film a promising NACs sensor.In Chapter 6, a fluorescence behavior controllable conjugated polymer (CPs)-based fluorescent film was developed by chemically attaching poly(2,5-dihexadecyloxy-phenyleneethynylene) (M-PPEs) onto a glass plate surface. It was revealed that the profile of the fluorescence emission spectrum of the film depended upon the polarity of its medium. This dependence has been attributed to the alteration of the conformation of the side chains of the polymer in immobilized state. In "poor" solvents or vapors, the side chains may adopt a compact coil conformation, resulting in aggregation of the immobilized polymers and thereby fluorescence emission of the film is reduced because of the so called aggregation induced fluorescence quenching effect. Whereas in "good" solvents or vapors, the side chains tend to be swollen and adopt extended or loose coil structure, and thereby preventing the aggregation of the polymers, coupled with increasing the fluorescence emission. Interestingly, this alteration process is fully reversible, and the retention time for each equilibration is less than 1 min. The film is also responsible for the changes in the compositions of mixture solvents, such as THF/methanol. In particular, a two-input INH and OR logic gates were presented on the basis of the film. No doubt, this finding can be taken as a new strategy for the design of CPs and self-assembled monolayer (SAM) based fluorescent sensing films, and will definitely expand their applications.In Chapter 7, a fluorescent conjugated polymer (CPs)-based amino acid chemsensor has been built up successfully by using "turn-on" strategy. The sensing performances were determined by the "proper interaction" between functional groups of polymers and copper (Ⅱ) ions. Obviously, the imidazole-functionalized CPs, P2, is a perfect sensing material to fabricate the amino acid chemsensors.In the appendix, a highly sensitive and portable explosive detector was created, which was based on the sensing films prepared in Part 2 and 3. The basic structure was provided in this chapter. No doubt, the economical, stable and portable detector with high-quality performance would gain extensive applications in the fields of environmental monitoring, anti-terrorism and nonmetal landmine detection.The main contributions of the thesis are described as follows:(1) Expending the design strategies for fabrication of sensing films. It is found that the substrate played the key role in sensing process, which gave a new way to fabricate the similar sensing films.(2) Designing and synthesizing a class of new conjugated polymers, which have been proved that it is an effective method to enhance the sensing performances of sensing films.(3) It was demonstrated clearly that the combination of the advantages of fluorescent films based on mono-molecular-layer chemistry and those based on conjugated polymers is an effective and feasible way to create novel fluorescent film sensors. Further research work showed that altering the side chains can affect the fluorescence properties, which may be a new strategy to make high performance sensing films.(4) On the basis of the above-mentioned fluorescent sensing films, an economical, stable and portable explosive detector with high performance has been created in our lab.更多还原