【作者】 杨善丽；

【导师】 罗胜联；

【作者基本信息】 湖南大学 ， 化学工程与技术， 2014， 博士

【摘要】 电化学传感器是一种由感应元件和换能器组成的,基于待测物的电化学性质对目标物进行检测的分析系统。作为分析检测领域重要的技术,电化学传感器具有操作简便、价格低廉、选择性高、分析速度快、可进行在线分析等传统分析方法不可比拟的优势,已经在环境检测、食品工业、生物医学研究、发酵工业生产等领域得到了高度的关注和广泛的应用。本论文针对电化学传感器研究和环境分析检测中的一些关键问题,即如何高效、清洁地将材料固定到传感器上,如何快速、灵敏地检测五氯苯酚、甲基对硫磷、亚硝酸盐等环境污染物,通过变换不同的材料、使用不同的修饰方法制备出了一系列新型的电化学传感器,并将其应用于环境分析检测中。采用循环伏安(CV)、方波阳极溶出伏安(SWV)、时间-电流法(i-t)、差分脉冲伏安(DPV)等多种电化学技术,以及电致化学发光(ECL)、紫外可见分光光度法(UV-vis)、傅里叶红外光谱(FTIR)2荧光分光光度法(FL)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)等其他技术手段,详细研究了构建的电化学传感器的结构、性质及其检测性能。本论文主要研究工作如下：1.通过电化学还原的方法将氧化性碳量子点/氧化石墨烯(OCQDs/GO)一步电还原为碳量子点/石墨烯(CQDs/GR),同时由于OCQDs/GO与CQDs/GR溶解度的不同,制备出的CQDs/GR复合材料随之沉积在了电极表面。通过SEM、TEM、 FL、UV-vis、CV和ECL对CQDs/GR复合材料进行了表征,实验结果表明制得的CQDs/GR复合材料非常稳定,能使传感器保持很好的稳定性；同时由于石墨烯(GR)优良的导电性,放大了ECL信号,大大提高了传感器的灵敏度；并且GR巨大的比表面积增加了碳量子点(CQDs)负载量,整个复合材料表现出良好的ECL检测性能,最终成功实现了对五氯苯酚(PCP)的高灵敏特异性检测,检测线性范围为1.0x10-12～1.0×10-8M,检测下限达到1.0×10-12M。同时该传感器实现了对实际土壤中PCP的检测,说明该传感器具有良好的实际应用前景。本论文首次通过一步电沉积的方法,以GR为模板实现了CQDs的固定化,从而使传感器的重复使用成为可能；同时利用GR可以放大ECL信号的作用和CQDs对PCP特异性氧化的作用,实现了高灵敏特异性检测PCP的目的。该研究方法为检测环境中的持久性有机污染物质提供了一条可能的思路：调控量子点尺寸,通过寻找与目标检测物氧化电位相匹配的量子点,利用GR为量子点固定化模板,实现对环境中有机污染物的高灵敏特异性检测。2.首先将玻碳电极置于氧化石墨烯(GO)和壳聚糖(CS)的混合溶液中,接着通过一步电还原方法制备出稳定的石墨烯/壳聚糖(GR/CS)复合材料。GO的电化学还原过程消耗了H+,增大了电极附近溶液的pH值,从而使得CS变得不溶；同时由于GO电还原生成的石墨烯(GR)不易溶于水,因而最终GR与CS一起电沉积在玻碳电极表面上,并且由于浓度梯度差,保证了生成的GR/CS源源不断地被沉积到了在电极表面。实验结果表明,该GR/CS复合物可以用作固相萃取模板,对甲基对硫磷(MP)表现出良好的富集性能,并且基于其所构建的电化学无酶传感器能快速地实现对MP产生检测电流响应,在最优实验条件下,该GR/CS无酶传感器具有很宽的线性范围4.0-400ng/mL,检测限达到了0.8ng/mL。同时,该传感器具有良好的重现性,稳定性以及较好的选择性,为绿色、快速、简单、灵敏的检测有机磷农药提供了新的途径。3.将氧化石墨烯(GO)和碳纳米管(CNTs)分散到壳聚糖(CS)中,形成GO/CNTs/CS混合液。由于氧化石墨烯(GO)的电化学还原过程消耗了H+,增大了电极附近溶液的pH值,从而使壳聚糖(CS)变得不溶；而基于GO电还原生成的石墨烯(GR)也不易溶于水；同时酸化的CNTs表面带有大量的含氧官能团,电还原过程中导致大量含氧官能团被还原,使得CNTs水溶性变差,该性质与GR类似；由此,利用它们三者电还原前后溶解度不同的原理,通过电沉积的方法直接一步制备出了GR/CNTs/CS复合材料,并且由于浓度梯度差,保证了生成的GR/CNTs/CS源源不断地被沉积到了在电极表面。该种方法由于不涉及到化学还原过程中经常使用的一些有毒还原剂如肼等,因此对环境友好而且不会造成二次环境污染。结合GR、CNTs和CS的各自优点,该GR/CNTs/CS可以用作固相萃取模板,对甲基对硫磷(MP)表现出良好的富集性能。在最优实验条件下,该GR/CNTs/CS电化学无酶传感器对MP检测线性范围为2.0-500ng/mL,检测限达到了0.5ng/mL。并且该传感器不但稳定性和重现性良好,而且具有较强的选择性。4.由于π-π相互作用,可以利用DNA实现碳纳米管(CNTs)的功能化后,通过简单的直流电沉积方法将DNA/CNTs/Cu2+复合材料固定于玻碳电极表面。电沉积在玻碳电极表面的DNA/CNTs/Cu2+复合材料对亚硝酸盐(N02-)具有良好的电催化性能,由此构建出一个灵敏的N02-电化学传感器。为了获得最高的灵敏度,通过实验详细研究了沉积液中Cu2+浓度、DNA浓度、CNTs浓度、电沉积时间等电沉积条件以及pH值和应用电位等检测条件对N02-在DNA/CNTs/Cu2+玻碳电极上响应电流的影响。实验结果表明,在最优条件下,该DNA/CNTs/Cu2+电化学传感器对N02-的检测线性范围为3.0×10-8-2.6×10"3M,检测限为3.0×10-8M,响应时间在3s以内。并且该DNA/CNTs/Cu2+电化学传感器表现出良好的稳定性、重现性和抗干扰能力,因此具有巨大的实际应用前景。5.通过一步电还原的方法,将玻碳电极置于由氧化石墨烯(GO)、壳聚糖(CS)和葡萄糖氧化酶(GOx)组成的GO/CS/GOx混合溶液中,直接在电极表面制备出石墨烯/壳聚糖/葡萄糖氧化酶(GR/CS/GOx)新型纳米复合膜。整个过程仅需要几分钟,而且形成的GR/CS/GOx膜均匀且厚度可控。循环伏安实验结果表明,GR/CS/GOx膜中的GOx保持了自身良好的生物活性,可以与电极之间发生直接电子转移,从而能够进一步用于对葡萄糖的检测。在最优实验条件下,该GR/CS/GOx电化学传感器对葡萄糖的检测线性范围为4.0×10-7～2.0×10-3M,检测限为4.0×10-7M,与其他采用滴涂的方法得到的GR/CS/GOx传感器相比,检测限降低了50倍。同时该传感器具有良好的稳定性、重现性和抗干扰能力,利用该GR/CS/GOx电化学传感器对实际人血清样本中葡萄糖的检测效果令人满意,与医院生化分析仪器所得结果一致,实际应用的潜力非常巨大。更多还原

【Abstract】 An electrochemical sensor, which combines a sensing element and an energy transducer, is an analytic device that basing on the electrochemical property of the analyte. As an important technology of analytical chemistry, electrochemical sensor has been widely used in various areas, such as environmental monitoring, food testing industry, biomedical science, fermentation industrial production and so on, due to its simplicity, low-cost, high sensitivity, high selectivity, rapidity and potential ability for real-time and on-line analysis. Our work focused on the key issues of the fabrication of electrochemical sensor and its analysis detection in environment, that is, how to immobilize component onto the energy transducer surface efficiently and cleanly, how to detect the environmental pollutants including pentachlorophenol, methyl parathion and nitrite sensitively and rapidly. This paper is concentrated on the preparations of novel electrochemical sensors using various modified materials and modified methods, and their aplications in the field of environmental analysis detection. The electrochemical sensors have been investigated by cyclic voltammetry (CV), square wave anodic stripping voltammetry (SWV), current-time technique (i-t), differential pluse voltammetry (DPV), electrogenerated chemiluminescence (ECL), ultraviolet-visible spectrophotometry (UV-vis), fourier transform nfrared spectroscopy (FTIR), fluorescence spectrophotometry (FL), scanning electron microscopy (SEM), transmission electron microscopy (TEM), etc. The main points of this dissertation are summarized as follows:1. The oxidized carbon quantum dots/graphene oxide (OCQDs/GO) mixture has been reduced into carbon quantum dots/graphene (CQDs/GR) hybrid by one-step electrochemical reduction technology. The obtained CQDs/GR hybrid is attached onto the electrode surface directly, utilizing the difference of the solubility between OCQDs/GO and CQDs/GR. The proposed CQDs/GR hybrid has been investigated by SEM, TEM, FL, UV-vis, CV and ECL. The experimental results show that the structure of the CQDs/GR hybrid is very stable which ensures the stability of the ECL sensor in practical application. The sensitivity of the ECL sensor has been greatly enhanced, owing to the good conductivity of GR which can amplify the signal, meanwhile, a large amount of CQDs can be absorbed onto GR due to the large specific surface area of GR. The CQDs/GR sensor shows good ECL property and enables the real-time detection of pentachlorophenol (PCP) with unprecedented sensitivity reaching 1.0×10-12M concentration in a wide linear range from1.0x10-12～1.0x11-8M. The ECL sensor shows high selectivity to chlorophenols (CPs)，especially to PCP. The practicability of the sensing platform in real soil samples shows ideal recovery rates. Herein, for the first time, through one-step electrochemical reduction technology, GR serves as both the ECL amplification reagent and the immobilization platform for CQDs, which not only enhance the detection sensitivity but also achieve the recyclability of CQDs. This work may present an important strategy to design QDs ECL sensors and expand their applications in ultratrace environmental sensing.2. Firstly, the glassy carbon electrode is immersed into the mixture of graphene oxide (GO) and chitosan (CS), and then the stable graphene/chitosan (GR/CS) composite is obtained by one-step electrochemical reduction technology. The proton consumption during electroreduction of GO increases the local solution pH near the electrode surface, leading to the insolubility of CS. Meanwhile, the obtained GR is insoluble in aqueous solution, thus co-deposition of GR and CS is achieved. The GR/CS composite can capture methyl parathion (MP) efficiently and be used as solid phase extraction, thus the goal for MP sensing is achieved. Under the optimal conditions, the proposed sensor exhibits a wide linear range from4.0～400ng/mL, and a low detection limit of0.8ng/mL. Moreover, the proposed sensor shows good reproducibility, long-time stability and satisfactory anti-interference ability. The obtained GR/CS sensor opens a new opportunity for green, fast, simple and sensitive detection of organophosphate pesticides.3. Graphene oxide (GO) and carbon nanotube (CNTs) are dispersed in chitosan (CS) solution to form a GO/CNTs/CS mixture. The proton consumption during electroreduction of GO increases the local solution pH near the electrode surface, leading to the insolubility of CS. The obtained graphene (GR) is also insoluble in aqueous solution. Meanwhile, the surface of CNTs owns large amounts of oxygen-containing functional groups after acidification, which can be reduced during the electroreduction process, resulting in the insolubility of CNTs. Thus, co-electrodeposition of GR. CNTs and CS is achieved. The GR/CNTs/CS composite can capture methyl parathion (MP) efficiently and be used as solid phase extraction, thus the goal for MP sensing is also achieved. Under the optimal conditions, the proposed sensor exhibits a wide linear range from2.0～500ng/mL, and a low detection limit of0.5ng/mL. The proposed sensor shows good reproducibility, long-time stability and satisfactory anti-interference ability.4. Carbon nanotube (CNTs) are functionalized by DNA through the π-π interactions between the nanotube sidewalls and the nucleic acid bases, and then the DNA/CNTs/Cu2+hybrid is fixed onto glassy carbon electrode through electrodeposition under controlled dc potential. Electrochemical experiments reveal that the DNA/CNTs/Cu2+hybrid showed high electrocatalytic activity to the reduction of nitrite (NC2-), thus a sensitive sensor for the determination of NO2-is constructed. Effects of the electrodeposition conditions such as the concentration of Cu2+, DNA, CNTs and electrodeposition time and the determination conditions such as applied potential and pH value on the current response of the proposed DNA/CNTs/Cu2+sensor toward NO2-have been optimized in order to obtain the maximal sensitivity. Under the optimal conditions, the response is fast (less than3s), the linear range of the determination of NO2-is from3.0×10-8～2.6×103M, and the detection limit is3.0×10-8M. Moreover, the DNA/CNTs/Cu2+sensor shows good stability, high reproducibility and well antijamming capability, thus the proposed sensor may have great actual application prospect.5. Graphene oxide (GO), chitosan (CS) and glucose oxidase (GOx) are mixed together directly to form a graphene oxide/chitosan/glucose oxidase (GO/CS/GOx) solution. The stable graphene/chitosan/glucose oxidase (GR/CS/GOx) film can be obtained on the glassy carbon electrode by one-step electrochemical reduction technology. The procedure takes only several minutes, and the thickness of the resulting film is uniform and controllable. Since good bioactivity of GOx is achieved and the reversible2-proton and2-electron transfer between glucose and GOx is also exhibited, the GR/CS/GOx hybrid can be used for glucose sensing. The biosensor has a detection limit of4.0×10-7M (50-fold lower compared to the biosensor prepared by drop-casting method), and the response linear range is4.0×10-7～2.0×10-3M. The GR/CS/GOx biosensor shows good stability, high reproducibility and well anti-interference ability.更多还原