【作者】 张昊；

【导师】 崔华；

【作者基本信息】 中国科学技术大学 ， 分析化学， 2010， 博士

【摘要】 论文首先综述了电致化学发光、离子液体、金属纳米材料／纳米复合材料以及纳米电致化学发光生物传感器的发展现状。电致化学发光新体系和机理研究一直受到人们的关注,新的电致化学发光体系的发现,有利于进一步拓展电致化学发光的分析应用潜力。而金属纳米材料作为纳米生物传感器中新型的建筑单元,对传感器的稳定性、重现性和灵敏度均起着重要作用。因此,本论文一方面针对吖啶类化合物,探索其电致化学发光新体系,并研究其发光规律和机理,最终将新体系作为检测手段构建纳米电致化学发光DNA传感器；另一方面合成离子液体保护的金属纳米粒子和复合纳米材料,对新材料中的作用机理进行研究。主要研究内容如下1.与水相中的电致化学发光行为相比较,光泽精在乙醇溶液中可以得到三个新的阳极发光峰(ECL-2-4)。对所得循环伏安曲线进行微分处理,并借助于线性扫描、预电解等多种电化学手段,对多个发光峰进行表征和分析,提出了各个发光通道的反应机理。ECL-2 (-0.53 V vs. SCE)可能对应于光泽精与过氧化氢电还原过程中产生的自由基O2·-之间的发光反应；ECL-3 (0.20 Vvs. SCE)可能对应于N，N-二甲基-9,9’-双吖啶烯(DBA)电氧化产生的自由基Luc·+与溶解氧之间的发光反应；ECL-4(0.51 Vvs. SCE)则为在溶解氧存在下,自由基Luc·+去质子化产生的DBA异构体与光泽精之间的发光反应。新产生的发光峰都与自由基相关,可能因为相对于水相而言,自由基可以在乙醇相中存活更长时间；另一方面光泽精的还原产物在乙醇中有更好的溶解性,因而更容易被电氧化并诱导电致化学发光。该项研究对光泽精电致化学发光基础理论研究具有重要意义。2.首次发现了光泽精与三丁胺体系的电致化学发光行为,在阳极可以产生一个新的电致化学发光峰并伴有两个肩峰。通过研究溶剂、电极材料、试剂浓度、气氛、电解质等因素的影响,我们推测ECL-1 (0.91 Vvs. SCE)和S1(0.52 V vs.SCE)对应于光泽精与TBA电氧化产物之间的发光反应,而反应所得的中间体则可进一步与光泽精发光并产生S2(1.19 V vs.SCE)。ECL-2 (0.66 Vvs. SCE)、S3(0.33 V vs.SCE)、S4(1.07 V vs.SCE)则为ECL-1、S1、S2各自的对峰,具有同样的反应机理。另外我们还研究了多种胺类化合物如三丙胺、三乙胺等与光泽精之间的电致化学发光行为。发现对于脂肪胺而言,随着三级胺脂肪链长的增加,发光光强也随之增加。随着脂肪链数量的减少,发光光强表现为叔胺大于仲胺大于伯胺。该项研究为设计吖啶类发光化合物新型电致化学发光反应体系提供了新的研究思路。3.首次发现三丙胺可以引发吖啶酯标记物的电致化学发光。推测该过程为三丙胺电氧化后产生的自由基进攻吖啶环9位,诱导吖啶环发生多重键裂生成激发态的N-甲基吖啶酮,并最终跃迁回基态产生发光。成功将该反应作为检测体系,以“夹心法”构建新型电致化学发光DNA传感器。对基于吖啶酯/三丙胺体系构建的DNA传感器进行初步的实验条件优化后,对模板DNA链进行定量分析。最优条件下,该DNA传感器的线性范围在5.0×10-15.mol·L～5.0×10-12 mol·L-1之间,检测限(S/N=3)为3.0×10-15mol·L-1,并且对单碱基错配、双碱基错配和完全错配DNA序列进行了研究,发现这些序列产生的ECL信号明显低于完全互补配对的目标DNA序列,表明该传感器具有良好的选择性。该项研究在临床分析中具有重要的应用潜力。4.成功地在水相中合成了羧基和氨基功能化离子液体保护的金/铂纳米颗粒。当用硼氢化钠作还原剂时,可以得到较小粒径的纳米金(3.5nm)和纳米铂(2.5 nm)；当柠檬酸钠作还原剂时,可以得到多种粒径的较大颗粒纳米金(23,42和98 nm)。我们采用透射电镜、紫外-可见吸收光谱、X射线光电子能谱等手段表征所得纳米粒子的形貌和表面状态,发现离子液体在保护纳米颗粒时,会使金属表面的电子云向咪唑环偏移,导致离子液体的C 1s和N 1s电子能谱发生负移。我们推测其保护机理可能有三种模型：(1)通过咪唑阳离子与金属表面负电荷之间的静电相互作用。(2)功能化基团与金属表面原子间的作用。(3)模型1和2两种作用力共同作用。所合成的金属纳米颗粒均可以吸附于未处理的多壁碳纳米管之上,形成复合纳米材料。该材料的形成可能与咪唑环和碳管表面之间的阳离子-π或π-π共轭作用有关,离子液体在金属纳米颗粒和碳管之间相当于起了一个连接试剂的作用。吸附实验过程中没有加其它的化学试剂,碳纳米管也不用经过酸化或其它处理步骤,而所得到的复合纳米材料仍然有较好的亲水能力,这种材料在催化、纳米电子学及传感器等领域具有重要的应用潜力。另外,与相同粒径柠檬酸钠保护的纳米金相比,离子液体保护的纳米金有更低的散射强度,这为进一步提高基于纳米金光散射测定DNA、氨基酸及染料的分析方法的灵敏度奠定了良好基础。5.首次成功地在室温下,在水相中用化学法一步还原出离子液体保护的多晶形纳米金。在氨基功能化离子液体存在的情况下,用单宁酸室温下还原氯金酸,可以得到在长波处(大于600 nm)有明显表面等离子体共振吸收峰的纳米金。由透射电镜照片可知,该吸收峰由金溶胶中的非球形纳米金导致。溶胶中非球形金主要由金三角片、十面体和二十面体组成。通过改变还原剂的量,可以实现对多晶形纳米金的晶形组成和尺寸进行调控。我们推测多晶形的产生跟多羟基还原剂单宁酸有关,而离子液体由于其自身的特性,对非球形纳米金的生成也有很大贡献,起到了合成模板的作用。此项工作丰富了人们对离子液体在纳米金形貌控制上的认识。更多还原

【Abstract】 In this dissertation, the state of arts in the field of electrochemiluminescence (ECL), ionic liquid (IL). metal nano-materials/nano-hybrids and nano-based ECL biosensor were reviewed.For ECL-based biassays, new electrochemiluminescent system is an important subject. Besides, metal nanoparticles play an important role in the nano-based biosensor, which can affect the stability, repeatability, and sensitivity of the sensor. Therefore, in the present dissertation, acridine compounds were utilized to design new ECL systems. The ECL behaviors, rules, and mechanisms of these novel ECL systems were investigated. Moreover, based on the new ECL system, a biosensor was developed to determine DNA. On the other hand, IL stabilized metal nanoparticles/nanohybrids were synthesized. The interactions among metal nanoparticles, IL and carbon nanotubes were also explored.The main results are as follows:1. Compared with the ECL of lucigenin in aqueous solution, three new anodic ECL peaks (ECL-2 at-0.53 V, ECL-3 at 0.20 V, and ECL-4 at 0.51 V) were observed. Depending on the semi-derivative voltammogram curves and different electrochemical techniques such as pre-electrolyzing and linear sweep voltammetry, the ECL peaks were characterized and the mechanisms were proposed. ECL-2 was likely due to the luminescent reactions between lucigenin and the radicals O2 generated during the electro-reduction of hydrogen peroxide. ECL-3 was possibly due to the luminescent reactions between Luc*+generated by the electro-oxidation of N,N’-dimethyl-9,9’-biacrylidene (DBA) and dissolved oxygen. ECL-4 was possibly due to the reaction between the DBA isomer and lucigenin in the presence of dissolved oxygen. The novel ECL peaks were related to radicals. The radicals can exist longer in non-aqueous solution than aqueous solution. And the reduction products of lucigenin have preferred dissolution ability in ethanol than H2O. Therefore, these differences might induce the novel ECL peaks in ethanol solution.2. The ECL behavior between lucigenin and tributylamine (TBA) was firstly studied. A novel anodic ECL peaks with two shoulders was observed. The effects of various factors such as media, material of electrode, concentration of lucigenin and TBA, atmosphere, and electrolytes on ECL peaks were examined and the mechanisms were proposed. ECL-1 (0.91 V vs. SCE) and S1 (0.52 V vs. SCE) were possibly due to the luminescent reactions between lucigenin and the electro-oxidized products of TBA. And the intermediate species could also react with lucigenin and generate S2 (1.19 V vs. SCE). ECL-2 (0.66 V vs. SCE), S3 (0.33 V vs. SCE), and S4 (1.07 V vs. SCE) were the counter-peaks of ECL-1, S1, and S2, respectively. Therefore, those peaks had the same luminescent processes with the counter-peaks. Moreover, the ECL behavior between several amines (such as tripropylamine and triethylamine, etc.) and lucigenin was examined. It was found that the ECL intensity decreased either as the length of aliphatic substituents decreased, or as the number of aliphatic chains decreased. The present work provides a way to design the ECL system of acridine compounds.3. It was found that tripropylamine (TPA) could induce the ECL behavior of acridinium ester (AE) labels. The radicals generated in the electro-oxidation process of TPA attacked 9 position of acridine, which would induce the multiple bond cleavage of acridine and generate excited.N-methylacridone. The excited N-methylacridone returned to ground state and released photons. The AE/TPA ECL system was used as the detection system for developing a sandwich-type ECL-based DNA sensor. The experimental conditions were optimized when a model DNA was chosen as a target analyte. Under the optimized conditions, the linear range of the DNA sensor was from 5.0×10-15 mol·L-1 to 5.0×10-12 mol·L-1. The detection limit (S/N= 3) was 3.0×10-15 mol·L-1. Moreover, the ECL-DNA sensor could selectively detect the model DNA among the one-base mismatched DNA, two-based mismatched DNA, and non-complementary DNA. It is of great application potential in clinic analysis.4. Carboxylic acid-and amino-functionalized ionic liquids were used as the stabilizer for the systhesis of metal nanoparticles in aqueous solution. Smaller gold nanoparticles (3.5 nm) and platinum nanoparticles (2.5 nm) were prepared with NaBH4 as the reductant. Larger gold nanospheres (23,42, and 98 nm) were synthesized using different quantities of trisodiumcitrate reductant. The morphology and the surface state of the metal nanoparticles were characterized by high-resolution transmission electron microscropy, UV-visible spectroscopy, and X-ray photoelectron spectroscopy. It was found that the electron clouds inclined to transfer from the metal surface to imidazolium ring, which induced the negative shifts in C 1s and N 1s binding energies. It was deduced that the nanoparticles were stabilized via three possible modes:(1) The electrostatic interaction between the imidazolium cation in ILs and the negatively charged metal atom. (2) The coordination between the functional group in ILs and metal atoms. (3) The simultaneous coordination mode involved in both (1) and (2). All the IL-stabilized metal nanoparticles were found to easily decorate on untreated multiwalled carbon nanotubes. In the microstructure of the nanohybrids, the imidazolium ring moiety of ILs might interact with theπ-electronic nanotube surface by virtue of cation-πand/orπ-πinteractions, and the functionalized group moiety might interact with the metal nanoparticles surface. The ILs acted as a linker. During all the decoration procedures, no additional reagents were needed, and the carbon nanotubes were used without any treatment. Moreover, the obtained nanohybrids had a remarkable hydrophilic ability, which might find future applications in fields such as catalysis, nanoscale electronics, as well as sensors. Additionally, amino-functionalized IL stabilized gold nanoparticles showed lower resonance Rayleigh scattering intensity than trisodiumcitrate stabilized gold nanoparticles, which may have potential application in DNA, amino acid, and dye analysis based on resonance Rayleigh scattering technique.5. Ionic liquid stabilized anisotropic gold nanoparitcles were synthesized by one-step chemical reduction method in aqueous solutions at room temperature. In the presence of amino-functionalized ILs, gold nanoparitcles with long-wavelength surface plasmon resonance (SPR) absorption (> 600 nm) could be obtained by using of tannic acid as a reductant. The specific SPR absorption was related to the non-spherical gold nanoparticles including gold triangle, decahedra, and icosahedra nanocrystals, which could be observed by transmission electron microscropy. The component and the size of the anisotropic gold nanoparitcles could be adjusted by the amount of reducing agent. It was deduced that the formation of non-spherical gold nanoparticles was related the hydroxyls in tannic acid, and ILs acted as the synthesis template because of the specific interactions between IL and gold surface.更多还原