【作者】 陈雷；

【导师】 张玉君； 徐蔚青；

【作者基本信息】 吉林大学 ， 电磁场理论与微波技术， 2004， 硕士

【摘要】 在当今社会，几乎没有任何一种科学技术的发展和应用能够离得开传感器和信号探测技术的支持。为了能够与信息时代信息量激增、要求捕获和处理信息的能力日益增强的技术发展趋势保持一致，对于传感器性能指标（包括精确性、可靠性、灵敏性等）的要求越来越高。随着插入技术的日趋成熟，敏感光纤技术的在传感器领域扮演着越来越重要的角色。光纤传感器的工作原理是将光作为信号载体，并通过光纤来传送信号。由于光纤对光具有良好的传导性能，损耗极低，加之光纤传输光信号的频带非常宽，且光纤本身就是一种敏感元件，所以光纤传感器所具有的许多优良特征为其它所有传统的传感器所不及。概括来讲，光纤传感器的优良特征主要包括重量轻、体积小、敏感性高、动态测量范围大、传输频带宽、易于转向作业以及它的波形特征能够与客观情况相适应等诸多优点，因此能够较好地实现实时操作、联机检测和自动控制。Surface-enhanced Raman Scattering(SERS)的发现引起了科学界的普遍关注和广泛兴趣，从而使拉曼光谱变成了研究分子结构和各种物质微观结构的重要工具。因为它不但能检测出单分子层甚至亚单分子层的物质，还能在分子水平上给出关于物质结构的丰富信息。光纤与表面增强拉曼(SERS)光谱技术的结合构成了光化学传感器的一个分支——表面增强拉曼光谱光纤传感器。它是建立在光谱化学和光学波导与量测技术基础上的，将分析对象的化学信息以吸收、反射、荧光或化学发光、散射、折射和偏振光等光学性质表达的传感装置。表面增强拉曼光谱光纤探针具有许多优势, 如: 提供丰富的分子结构信息; 不怕水的干扰; 对于某些危害人身体健康而不易直接接触的场所可以进行远距离遥测; 还可以实时监测某些化学反应以研究其动力学机理; 也可作为某些危险和污染过程的实时监测手段。表面增强拉曼(SERS)光纤探针还可以与其它的传感器互补使用。 <WP=67>我们所研究的EF-SERS光纤传感器是表面增强拉曼光纤传感器的一个新的应用，除了具有表面增强拉曼光纤传感器的优点之外还具有消失场检测的优点，减少了背景的干扰，提高了信噪比。我们通过对组装金属修饰层后的EF-SERS活性拉曼光纤探针的理论分析，发现光纤内全反射产生的消失波和金属膜表面电子集体振动产生的表面等离子波在一定的条件下产生表面等离子共振，在共振状态下金属颗粒的周围产生很强的局域场，而探针分子在这种增强的局域场的作用下就会产生增强的拉曼散射信号，我们通过对乙烯吡啶和1, 4 – bis [2 - (4 -pyridyl)ethenyl]-benzene (BVPP)等化合物进行了原位检测, 取得了较好的结果。我们还设计了一种应用于低折射率溶液测试的EF-SERS活性拉曼液芯光纤探针，通过对BVPP的检测发现这种新型的液芯光纤传感器具有较高的灵敏度。本论文工作的研究内容主要包括：EF-SERS活性拉曼光纤传感器修饰层的局域场增强理论计算光纤内传播的光在纤芯和包层之间产生消失场，我们以低折射率的溶液代替包层，这样消失场就会作用于溶液中穿透深度内的样品，由于消失场的强度比较弱，它激发的样品的拉曼散射信号很难被检测到，我们在光纤表面修饰金属膜层（50纳米左右），在激发光的作用下金属膜的表面电子集体振荡产生表面等离子波，当等离子波的波矢量和消失波的波矢量相匹配的条件下就产生表面等离子共振效应。我们采用准静态近似，计算了共振效应时在金属颗粒的周围产生增强的局域场，而且计算了场增强的效果与粒子大小、周围介质、粒子的形状的关系。位于增强局域场作用范围内的探针分子受激发就能产生增强的拉曼散射信号。基于这种原理我们设计了EF-SERS光纤传感器。 <WP=68>2、光纤传感器的设计和加工工艺使用刻蚀的方法制备了光纤探针，光纤探针加工工艺大致可以分为如下几步: 切割, 打磨抛光, 清洗, 刻蚀, 清洗, EF-SERS活性修饰等。利用银溶胶自组装膜方法对光纤探针作了EF-SERS活性修饰。银溶胶通过N-金属键自组装到光纤探针表面, 形成一层稳定均匀的溶胶膜。通过模拟，我们得到了溶胶的最佳组装时间应该在16小时以上。组装到光纤上之后, 溶胶膜同时具有金属溶胶的光学性质和固体底物的便利。它在保留了溶胶一定程度的聚集的同时，还克服了溶胶不稳定、易沉降的缺点, 可以很大程度增强拉曼信号; 既显示出优良的增强能力, 又利用了光纤的特点。3、光纤传感器的原位检测、响应时间、检出限等特性利用EF-SERS活性拉曼光纤探针对乙烯吡啶, 1, 4 – bis[2 - (4 -pyridyl)ethenyl]-benzene (BVPP)等化合物进行了在位检测, 取得了较好的结果。检出限是拉曼光纤探针的重要性能指标之一。我们测得了EF-SERS活性光纤探针对BVPP在氯仿溶液中的检出限为: 1 ( 10-9 M/L。光纤传感器的平均使用寿命为5次。银溶胶自组装EF-SERS活性拉曼光纤在蒸馏水中可以放置5 ~ 6天。在空气中可放置36 h。我们设计了一种应用于低折射率样品测试的EF-SERS液芯光纤传感器，它和拉曼光谱仪联合应用对BVPP的甲醇溶液进行检测，得到了低浓度下样品较好的拉曼光谱，通过对实验数据分析，给出了检测应该低于1 ( 10-8M/L。更多还原

【Abstract】 As we all known, there is evanescent field when the light takes internal total reflection on the interface of the rare medium and the denser medium. In this thesis, we designed a Optical Chemical Sensor based on the evanescent field (EF) in the optical fiber.Surface-enhanced Raman scattering (SERS) has long been a matter of great concerns since its discovery in 1974. As a powerful spectroscopy analysis tool, SERS has many excellences over other analysis tools, though scientists have not understood its essential mechanism completely. SERS has been applied extensively in various important fields (molecule surface absorption, biochemistry, corrosion-proof of metal, high polymer materials, thermal breakdown and catalysis, trace analysis, photo conducting device and LB film, etc.).The sophisticated technologies on fiber optic manufacture and application have also been developed in recent years. All these put the foundation to the development of SERS optic fiber sensor. The combination of the optic fiber and the technology of the SERS spectroscopy, one of the evolvements to Optical Chemical Sensor (OCS).In this thesis we used the EF as exciting field, thus the surface plasma resonance between the evanescent wave and the surface plasma produced on the metal film can induced the enhanced field under the function of the evanescent field. In fact, belonging to the OCS, the EF-SERS fiber sensor is one of the important branches of SERS spectroscopy. OCS, expressing the chemical information from the analytes by optical properties such as, absorption, reflection, fluorescence or chemical luminescence, scattering, refraction and polarization, are transduced setups that are based on the spectroscopy chemistry and optics waveguide and the technique of measurement the EF-SERS optic fiber sensor has many advantages. For example, giving more information on the molecular structure, reducing the effect of background, providing remote sensing to the harmful environment, in situ monitoring the reaction process for the kinetic mechanism, also in situ monitoring some danger process. It can be used as the complemental sensor to other sensors at the same time.The thesis consists of the following contents:We calculated the enhanced factor of the local field by SPR between the surface plasma wave and the evanescent wave in the EF-SERS fiber sensor. The dielectric function of some metals at optic band is analyzed. The result of <WP=70>calculation demonstrates that Ag is the best metal for surface enhanced Raman scattering. On roughed Ag surface, Raman spectrum can be increased by six orders of magnitude, when surface plasma resonance (SPR) is excited. Analysis also demonstrate that some factors effect the SPR very much.The calculation showed that the factor was related to the following parametera、The dielectric constant out of metal particleWhile the dielectric constant out of the metal particle increase, the frequency of SPR shift to low frequency (LF). And the enhancement of located EM field also increases.b、The shape of the metal particleIf the Ag particle is ellipsoidal, the frequency of SPR will shift to LF while the ratio of major axis to minor axis increases.c、The size of the metal particleOn sphere condition, the variety of enhancement is up first, then down.2、The design and the crafts of the EF-SERS fiber sensor optic fiber sensorThe EF-SERS fiber sensor were designed and studied. The fabrication craft concludes cutting, polishing, washing, embellishing and reservation. The key process is embellishing, so the optimized condition is researched. The method through Ag colloid is easier and simplier than that of Ag island film. The assembly of silver colloid particles onto the fiber by N-metal bond formed a homogeneous and stable film. Self-assembled Ag colloid film had both the optical properties of colloidal particles and the convenience of the solid substrate after absorbed onto the fiber tip. It preserved the aggregation at some degree while avoiding being subject to aggregating to deposit and the unstab更多还原