节点文献
基于电子授受作用的硝基芳烃检测用薄膜荧光传感器的设计、制备和传感性能
【作者】 李慧慧；
【导师】 房喻；
【作者基本信息】 陕西师范大学 ， 物理化学， 2008， 硕士
【摘要】 硝基芳烃是常见爆炸物和典型的有机污染物,具有突出的公共安全威胁性、生态破坏性和生物毒性,也是潜在的致癌物质。因此研究微痕量硝基芳烃的快速检测新方法,对于及时发现隐藏炸药,预防恐怖犯罪,跟踪环境质量都具有十分重要的意义。目前见著文献的检测硝基芳烃的传感器中,以共轭荧光聚合物作为传感元素的薄膜荧光传感器被人们研究得最为深入。这是由于这类荧光物质具有所谓的“分子导线”或“一点接触、多点响应”效应。此类薄膜具有良好的光稳定性,超高的检测灵敏度,尤其适用于对气相硝基芳烃类化合物的检测。但是也存在一些突出缺点。主要是薄膜通透性不好:且由于荧光物种泄露的缘故,薄膜难以用于溶液样品测定。因此,有必要发展新的薄膜荧光传感器,克服共轭荧光聚合物薄膜存在的缺陷。本论文的研究工作拟采用自组装单层膜（self-assembled monolayers SAMs）技术,将荧光小分子多环芳烃化学固定于玻片表面,制备既能用于气相又能用于液相硝基芳烃检测的薄膜荧光传感器。选用具有富电子特征的多环芳烃作为传感元素的主要考虑是:缺电子硝基芳烃和多环芳烃之间存在电子授受作用,能猝灭薄膜的荧光发射,而且有助于硝基芳烃在薄膜表面的聚集,提高检测的灵敏度。由于SAMs膜高度的稳定性和结构特点,确保了此类薄膜在使用中基本没有荧光物种泄露;且传感元素暴露在薄膜表面可以直接与待分析物作用,在理论上不存在通透性问题.基于以上考虑和本实验室已有的研究基础,本论文的第一部分研究采用SAMs技术,以芘为传感元素,将其经由柔性长连接臂共价结合在以环氧基为功能末端的玻片表面,制备了一种对硝基芳烃蒸汽敏感的荧光传感薄膜。与已有的对硝基芳烃化合物敏感的荧光薄膜相比,该薄膜的不同之处在于连接臂微结构的不同,柔性和长度均有所增加。荧光猝灭实验表明,该薄膜的检测灵敏度主要与待检测硝基芳烃化合物的饱和蒸汽压及其分子体积有关,其对常见炸药的标示物如三硝基甲苯和2,4-二硝基甲苯在空气中的最低检出限分别为7.14×10-12和5.49×10-11g·mL-1。相对于采用较短柔性连接臂的薄膜,以柔性长链为连接臂的传感薄膜对硝基芳烃的响应速度较慢,但是对硝基芳烃化合物的分子体积表现出一定的选择性,较小体积的硝基芳烃更容易接近膜内的传感元素,猝灭其荧光。此外,苯、甲苯、乙醇和香水等对测定均无明显干扰。该膜对硝基芳烃类化合物的响应还具有良好的可逆性,为其实际应用提供了可能。本论文的第二部分工作以丹磺酰为传感元素,同样采用SAMs技术,将其经由长柔性连接臂化学组装于以环氧基为功能末端的玻片表面,制备了一种可用于液相硝基芳烃检测的薄膜荧光传感器。该薄膜稳定性好,在液相中使用时,几乎不存在泄露问题。与短连接臂的类似薄膜相比较,该薄膜对硝基苯的传感性能有所不同。猝灭实验表明薄膜荧光在水相中对硝基苯的响应比三硝基甲苯,2,4-间二硝基甲苯,对氯硝基苯,对二硝基苯,间二硝基苯等其它硝基芳烃化合物更敏感。这可能是由于长柔性连接臂在水中采取压缩构象产生的屏蔽效应引起的.同时,实验中还证明硝基苯对薄膜荧光的猝灭过程在本质上属于静态猝灭,且具有较快的响应速度和良好的传感可逆性。
【Abstract】 Nitroaromatic compounds（NACs） are typical explosives and common organic contaminants which are a real threat to public security,terrible destroyers to environment and toxics to biological systems.Moreover,they are considered as potential carcinogens.So developing a sensitive sensor for detect trace amount of NACs has eminent significance for discovering hidden landmines,preventing terrorist attacks and monitoring environment qualities.Among NACs sensitive sensors reported in the documents,fluorescent conjugated polymer film sensors have gained the closest and the most extensive studies,due to its "molecular wire" or "wring molecular recognition sites in series" effect.These sensing films display high photo-stability and ultra-high sensitivity and it has been demonstrated to be effective sensor for the NACs in air.However,they also have unavoidable disadvantages,slow diffusion of analytes in the film system and leaching of the fluorophores,which make it hard to be used in solution systems.Therefore,developing novel fluorescent film sensors to avoid these problems is real in need.Our program in this dissertation was aimed to fabricate NACs sensitive fluorescent film sensors via chemically bonding the polycyclic aromatic on the glass plate in a SAMs way.Employing polycyclic aromatic as the sensing element is due to the donating and accepting interaction between the NACs and polycyctic aromatics,which will help the NACs close to the surface of the film and produce the fluorescent quenching of the film sensors.The SAMs technique to immobilize the fluorophores on the outmost layer of the SAMs-functional glass plate is an effective way to solve the leaching and diffusion problems.This is because a SAMs film displays high stability and sensing elements in these films can directly contact with analytes.Given the above consideration and the previous work in our group,a fluorescent film sensor for NACs vapors was designed in the first part of this dissertation.It was prepared by immobilizing the pyrene derivatives on the epoxide-terminated glass plate via long spacers in a SAMs way.As discovered in the study,the sensitivity of the film to the NACs analytes mainly depends on the vapor pressure of a given NAC and the quencher size.The detection limits to the common explosive vapors, 2,4,6-trinitrotoluene and 2,4-dinitrotoluene,are 7.14×10-12 and 5.49×10-11 g·mL-1,respectively. Compared to the film with shorter spacers,this film shows slower response to NACs,but higher selectivity to the quencher sizes.In addition,the response of the film to NACs is barely influenced by the presence of some common chemical vapors,such as benzene,toluene,ethanol and perfume. Moreover,the detecting process of the film for NACs is reversible,which promises its potential for practical applications.In the second part of this dissertation,another fluorescent film sensor for the detection of NACs in aqueous phase has been developed via chemical immobilization of dansyl group on an epoxy-terminated self-assembled monolayer on glass plate.Thank to chemical attachment of the chromophore on the substrate,the present film shows a satisfying stability and avoids the problem of leaching of the chromophores.Increasing the length of the spacers results in a dramatic improvement in the performance of the film compared to those with similar structures.Fluorescence quenching experiments demonstrates that in aqueous medium,the emission of the film is more sensitive to nitrobenzene than to other NACs,including 2,4,6-trinitrotoluene,2,4-dinitrotoluene, p-chloronitrobenzene,m-dinitrobenzene,p-dinitrobenzene,and etc.This exceptional result has been rationalized by considering the possible hindrance effect induced by the compact conformation of the long flexible spacer.It is also demonstrated that the nitrobenzene quenching is static in nature,and the response of the film to nitrobenzene is fast and reversible.