【作者】 张佳利；

【导师】 郭守武；

【作者基本信息】 上海交通大学 ， 材料科学与工程， 2011， 博士

【摘要】 石墨烯（Graphene）是由单层碳原子六方堆积而成的二维碳材料,具有理想的晶格结构和独特的电学、光学、力学和热学等性质,在电子器件、生物和化学传感器、储能器件及复合材料等领域有着广泛的应用前景。目前,石墨烯的制备方法主要包括:微机械剥离法、化学气相沉积法、外延生长法、氧化石墨烯溶液（Graphene Oxide,GO）还原法和有机合成法。与其它方法相比,氧化石墨烯溶液还原法具有成本低、产率高和可批量生产等特点,有望成为规模化制备石墨烯的有效途径之一。本论文针对目前GO溶液还原法制备石墨烯过程中存在的科学和技术问题,创新性地以具有较强还原能力和环境友好的抗坏血酸（L-AA）（维生素C）为还原剂,实现了GO的有效还原,制备出了具有较高还原程度的化学还原氧化石墨烯（Chemically Reduced Graphene Oxide,CRG）。由于其表面仍然残留有极少量的含氧基团,为了与严格意义上的石墨烯相区别,在此文中我们称之为化学还原氧化石墨烯,并在此基础上合成出了化学还原氧化石墨烯/聚乙烯吡咯烷酮（CRG/PVP）纳米复合物等。同时,对它们的组成、结构和电学性质,及其在酶固载和电化学传感等领域的应用进行了研究。主要研究内容及结果如下:（1）通过石墨插层氧化处理再超声剥离的方法制备出了单分散GO水悬浮液。利用原子力显微镜（AFM）、透射电镜（TEM）、红外光谱（FT-IR）、拉曼光谱（Raman）、X-射线衍射（XRD）、X-射线光电子能谱（XPS）和固体13C魔角旋转核磁共振（Solid State 13C Magic-Angle Spinning （MAS） NMR）对其化学组成、晶态结构和形貌进行了系统表征和分析。结果表明,所制备的GO具有单原子层结构,表面富含大量的含氧基团,在水中具有良好的单分散性。（2）在不添加任何稳定剂（Stablizer）的条件下,以具有较强还原能力和环境友好的抗坏血酸（L-AA）（维生素C）为还原剂,在水溶液中还原GO制备出了单分散的CRG。采用AFM、TEM、高分辨透射电镜（HRTEM）、紫外可见光谱（UV-vis）、FT-IR、Raman、XRD和XPS对其形貌和结构进行了表征,也通过四探针测量仪测定了CRG薄片的电导率;并利用导电原子力显微镜（CAFM）对单层CRG的电学性质进行了研究。结果表明,所制备出的CRG具有较好的导电性,并可以分散于水中形成稳定的悬浮液。（3）以水溶性高分子聚乙烯吡咯烷酮（PVP）和GO为原料,L-AA为还原剂及质子化试剂,经一步法合成出了CRG/PVP纳米复合物。采用UV-vis、Raman、XPS、Solid State 13C MAS NMR、示差扫描热量法（DSC）和热重分析法（TGA）对其结构进行了分析;采用AFM原位观察了单层CRG/PVP纳米复合物的水吸附能力;利用CAFM对单层CRG/PVP复合物薄膜的电学及湿敏性进行了研究。结果表明,通过简单的一步法成功将PVP接枝于单层CRG上形成CRG/PVP纳米复合物;单层CRG/PVP的导电性对环境相对湿度的改变十分灵敏。（4）在不加入任何偶联剂和不对表面进行任何修饰的条件下,实现了辣根过氧化物酶（HRP）在GO表面的有效固载。利用AFM原位观察了HRP在GO原子级平整表面的固载过程,以苯酚作为还原底物研究了固载酶的催化性质。结果表明,单层GO是一种理想的酶固载基底材料,HRP与GO官能团的相互作用决定着GO固载酶的催化效率。（5）采用电化学循环伏安法（CV）和微分脉冲伏安法（DPV）研究了部分还原氧化石墨烯（PCRG）固载HRP体系对玻碳（GC）电极的修饰和修饰后电极的电化学生物活性。结果表明,经L-AA还原GO制备的PCRG可以在不使用任何交联剂的条件下固载HRP并对GC电极进行修饰;其中CRG24H（GO还原24 h）是理想的电极修饰材料,促进了HRP与电极的直接的电子转移;基于HRP/CRG24H/GC的传感器对H₂O₂、苯酚和对氯苯酚都表现出很高的生物催化活性。更多还原

【Abstract】 Graphene is a two-dimensional carbon materials, which is composed of monolayer of carbon atoms tightly packed with hexagnol symmetry, and has excellent electrical, optical, mechanical and thermal properties, and holds great potential for applications in electronic device, chemical/biological sensors, energy storage devices, and composites. Up to now, there have been several fabrication routes to graphene, such as micromechanical exfoliation, chemical vapour deposition, epitaxial growth, the reduction of graphene oxide (GO) solution, and organic synthesis. In comparison, the reduction of GO solution has advantages over other approaches including easy processing, large-scale yield and low cost, and is expected to be an effective way for large-scale preparation of graphene.In this thesis, to overcome the current scientific and technical problems exist in reduction of GO, an innovative route using L-ascorbic acid (L-AA) (vitamin C) as a reducing agent, which have mild reductive ability and nontoxic property, to achieve effective reduction of graphene oxide, and prepare the chemically reduced graphene oxide (CRG) having higher degree of reduction. Because its surface remained a small number of residual oxygen groups, in order to distinguish strict graphene, in this thesis, we call it chemically reduced graphene oxide, and, additionally, the chemically reduced graphene oxide/poly(N-vinyl pyrrolidone) (CRG/PVP) nanocomposites and so on have been prepared successfully. Meanwhile, the compositions, structures and electrical properties, and applications in enzyme immobilization and electrochemical sensing were explored systematically. The main results are as follows: 1. We demonstrated that graphite could be intercalated and oxidized to form graphite oxide. The graphite oxide could be exfoliated by ultrasonication in water into individual graphene oxide (GO) sheets. The composition, structure and morphology of as-generated GO were characterized using atomic force microscopy (AFM), transmission electron microscopy (TEM), FT-IR, Raman spectroscopy, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and Solid-State 13C Magic-Angle Spinning (MAS) NMR. The results show that the as-prepared single-layered GO, has abundant oxygen-containing surface functional groups, and shows a good monodispersity in water.2. Using L-ascorbic acid as reductant, having a mild reductive ability and nontoxic property, the individual CRG sheets in water was prepared by the redction of GO without using any stabilizer. The morphology and structure of CRG were characterized using AFM, TEM, HRTEM, UV-vis, FT-IR, Raman spectroscopy, XRD and XPS. The electrical conductivity of CRG paper was measured by Four-Point probes, and the electrical conductivity of the individual CRG sheet was measured using conductive atomic force micr oscopy (CAFM). The results show that the prepared CRG has good electrical conductivity, and can be dispersed in water to form a stable suspension.3. Using water-soluble poly (N-vinyl pyrrolidone) (PVP) and GO as raw materials and L-AA as reductant and protonated reagent, the individual nanocomposite sheets of CRG and PVP, namely CRG/PVP, have been fabricated through a simple one-pot procedure. The structure of as-prepared CRG/PVP sheets were characterized using UV-vis, Raman spectroscopy, XPS, Solid-State 13C NMR, differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Water adsorption capability of individual CRG/PVP sheets was monitored in situ using AFM. The electrical conductivity of the individual CRG/PVP sheets was measured at different relative humidity (RH) using a CAFM system. The results show that the PVP molecules were chemically grafted on CRG surfaces, and the electrical conductivity of CRG/PVP sheet is sensitive to RH variation. 4. We illustrated that horseradish peroxidase (HRP) immobilization on GO sheets could take place readily without using any cross linking reagents and additional surface modification. The atomically flat surface of GO enabled us to observe the immobilized enzyme in native state directly using AFM. The catalytic activity of the immobilized HRP was assayed using phenol as catalytic reaction substrates. The results show that GO sheets is an ideal substrate for enzyme immobilization, and immobilized catalytic performance is mainly determined by the interactions of the enzyme molecules with the functional groups of GO.5. The electrochemical catalytic properties of glass carbon (GC) electrodes modified with PCRG (partially chemcailly reduced graphene oxide)-bound HRP were investigated by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The results show that PCRG, which were prepared by reduction of GO via L-AA, were able to immobilize enzyme firmly without using any cross linking reagents, and CRG24H (GO was reduced for 24 hours) was an ideal material for modification of GC electrode, and may promote the direct electron transfer between enemzy and electrode, and the sensor based on HRP/CRG24H/GC electrode exhibites high biological activity toward H2O2, phenol and p-chlorophenol.更多还原