基于霍尔效应的电致化学发光传感新技术的研究

Electrogenerated chemiluminescence (also called electrochemiluminescence and abbreviated ECL) is the process whereby species generated at electrodes undergo high-energy electron-transfer reactions to form excited states that emit light. After about 40 years study, ECL has now become a very powerful analytical technique and been widely used in the areas of, for example, immunoassay, food and water testing, and biowarfare agent detection. Because ECL is a method of producing light at an electrode, in a sense, ECL represents a marriage between electrochemical and spectroscopic methods. ECL has many distinct advantages over other spectroscopy-based detection systems. For example, compared with fluorescence methods, ECL does not involve a light source; hence, the attendant problems of scattered light and luminescent impurities are absent. Moreover, the specificity of the ECL reaction associated with the ECL label and the coreactant species decreases problems with side reactions, such as self-quenching. According to the different luminophor categories, ECL systems could be divided into inorganic systems (e.g., Ru(bpy)32+), organic systems (e.g., luminol), and nanocrystal (NC) systems. Due to the unique quantum size dependent electrochemical properties of NCs and controllable ECL merits, NCs have become more and more fascinating luminophors to contruct biosensors. NCs film generates strong, stable and tunable ECL signals, and is an ideal platform for ultrasensitive detection of biological targets because of its advantages such as easy modification with biomolecules and diverse interactions with other substances. However, current ECL technique mostly deals with biomolecular recognition or quantitative detection with little attention on molecular structures and intracellular components of biorelated species, although these molecular informations are closely related to human disease. In such case, the combination of ECL with other techniques is extremely desirable for the disease diagnosis, drug development.The Hall effect is the production of a voltage difference (the Hall voltage) across an electrical conductor, transverse to an electric current in the conductor and a magnetic field perpendicular to the current. The hall effect is also observed in semiconductors. So, this project creatively introduces the hall effect to ECL technique. In the existence of weak magnetic field applied, the relationship between molecular structural change and human disease will be studied. This project would open new insights into the understanding of the hall effect.

电致化学发光（ECL），是通过电化学反应直接或间接引发的化学发光现象，是电化学和光谱方法的完美结合，已被广泛应用于免疫、食品检验及基因检测等各个领域。近年来，各种高ECL发射效率的半导体纳米晶的研发,更为ECL应用领域的拓展提供了有力的支撑。不过，当前国际上纳米晶膜ECL的应用主要集中在生物分子的识别与定量方面。这种功能的实现大多数依赖于靶标分析物在膜ECL发光过程中的介入，因而对靶标分析物在分子识别定量检测过程中所经历的分子结构、性质改变等常不能给出有意义的信息。要成功地将纳米晶ECL应用于探知人类疾病的致病机理、治疗药物的筛选及生命物质的生物功能的开发、迫切需要电致化学发光传感新技术的出现。鉴于半导体材料中的显著霍尔效应和光学信号的灵敏性，本项目创新性地将霍尔效应引入到电致化学发光体系中，在弱外磁场存在下，研究生物物质结构、性质的改变与疾病的关系，扩展ECL技术的检测功能。

磁场与光发射过程的相互作用可以实现光过程的磁调控，从而建立以磁场效应为基础的磁性变化传感技术。本项目制备了具有稳定电致化学发光（ECL）的CdS纳米晶膜，通过不同碱基对数的DNA双链在纳米晶膜表面连接5 nm Au纳米粒子，构建ECL-LSP（局域表面等离子体）耦合体系。27、30、36、42、48碱基对DNA连接的CdS纳米晶-Au纳米粒子耦合体系的ECL强度分别是纯纳米晶膜ECL的1.3, 2.7, 6, 9 和3倍。耦合体系ECL的增强源于ECL-LSP的耦合引起的辐射复合速率的增加。100 μM Co2+离子能够将42碱基对DNA连接的CdS纳米晶-Au纳米粒子耦合体系的ECL猝灭达83%。ECL猝灭程度与Co2+离子浓度成正比。当在该体系中加入能够与Co2+离子反应的物质而导致Au纳米粒子表面的Co2+离子减少后，体系的ECL能够显著恢复。在此基础上，实现了5，10，15，20-四吡啶基卟啉和L-脯氨酸的灵敏检测。外加磁场对不同结构CdS纳米晶膜可产生正或负磁场效应，即能增强或猝灭CdS纳米晶膜的ECL强度。对于由CdS纳米晶颗粒组成的膜，ECL增强效率最大为85%；对于形成大量CdS纳米晶团簇的膜，ECL猝灭效率（ ）随着外加磁场的强度增加而增大，最大达-98%。出现正负磁场效应的原因是由于不同纳米晶膜结构下产生的内磁场方向不同而导致电化学还原产生的SO4-·(h+)空穴有不同的自旋方向。Fe3O4纳米颗粒（50 nm）和Co3O4/石墨烯复合颗粒（100 nm）对负磁场效应具有明显的扰动，且越靠近纳米晶膜表面扰动越大。在距离纳米晶膜表面14nm处，Fe3O4纳米颗粒（50 nm）仍有弱扰动，而Co3O4/石墨烯复合颗粒（100 nm）已几乎无影响。在CdS纳米晶膜表面，磁场强度弱于-100 GS时，Fe3O4纳米颗粒（50 nm）和Co3O4/石墨烯复合颗粒（100 nm）的磁场效应改变系数 均大于1，最大可分别达3.44和2.14。固定磁场强度为-54 GS，Fe3O4纳米颗粒（50 nm）为标记物，可实现抗原的灵敏检测。 与抗原浓度对数在0.5~1000 pg/mL-1范围内呈现很好的线性关系（R2=0.998）。本项目为检测弱磁性变化所用的设计和所得的实验结果对开发新的传感技术、研究光发射过程中的光-磁-LSP相互作用具有重要的启发作用。