【作者】 周康夫；

【导师】 朱以华；

【作者基本信息】 华东理工大学 ， 材料科学与工程， 2012， 博士

【摘要】 石墨烯是sp2杂化的碳原子构成的二维单原子片层,可以看作是碳族材料的基本组成单元。石墨烯的二维结构和长程π电子共轭赋予了其独特的热、机械以及电性质,因此石墨烯在理论研究与实际应用两方面都具有重要价值。本文针对生物传感器中存在的电子传递速率慢、酶活性难以保持等问题,通过引入石墨烯和金纳米粒子构成复合材料,来促进酶和电极间的电子传递并使酶保持催化活性,从而提高传感器的性能。同时,为制备具有特殊功能性的石墨烯基复合材料,本文以氧化石墨烯和金属盐前驱体为原料,通过溶剂热法制备了石墨烯-Fe3O4和石墨烯-TiO2复合材料,并考察了其应用性能。本文第二章通过化学法制备水溶性石墨烯。首先用常规的Hummers方法以及超声作用得到氧化石墨烯,在用水合肼还原氧化石墨烯之前,引入一步磺化过程,使最终得到的石墨烯表面带上磺酸基团(-SO3-),并利用此磺酸基团之间的静电排斥作用,使石墨烯在水中达到稳定分散。本文第三章利用制得的水溶性石墨烯,分别构筑新型的基于石墨烯的过氧化氢传感器和葡萄糖传感器。(1)将石墨烯和过氧化氢酶HRP分散于壳聚糖溶液,滴涂于玻碳电极表面形成一层均匀的生物膜,通过电镀在电极表面生长金纳米粒子。循环伏安显示此电极可以实现HRP的直接电化学,并且可以电催化H2O2的还原。此过氧化氢生物传感器响应时间小于3s,检测线性范围从5×10-6M到5.13×10-3M,检测限约为1.7×10-6M。(2)将石墨烯、预先制备好的金纳米粒子、葡萄糖氧化酶共同分散于Nafion溶液,并将此混合分散液滴涂于玻碳电极表面构筑葡萄糖生物传感器。在溶液中存在对苯二酚的情况下,此电极对葡萄糖的加入会产生一个快速响应的台阶电流,显示了典型的对葡萄糖的催化氧化反应。传感器的线性范围从15×10-6M到5.8×10-3M,检测限约为5×10-6 M。本文第四章以氧化石墨烯和金属盐前驱体为原料,通过溶剂热法一步制备石墨烯/金属氧化物的复合材料。(1)以氧化石墨烯和氯化铁为原料,通过溶剂热法制备了石墨烯/四氧化三铁复合材料(G-Fe3O4)。在反应釜内部的高温高压环境中,含氧基团被分解,氧化石墨烯被还原成石墨烯,同时,吸附于氧化石墨烯表面的铁离子也发生反应原位生成Fe3O4粒子。Fe3O4的大小和在石墨烯表面的分布密度可以通过原料中Fe3+的浓度来调节。所得的G-Fe3O4在室温下的饱和磁化强度可达45.5 emu g-1。G-Fe3O4可用于药物的负载和靶向投放,G-Fe3O4对阿霉素的饱和负载率达到了65%。以G-Fe3O4作为电极修饰材料构筑的过氧化氢生物传感器,也具有良好的性能。(2)以氧化石墨烯和钛酸正丁酯为原料,通过溶剂热法制备了石墨烯/二氧化钛复合材料(G-TiO2)。结果显示锐钛矿相的TiO2粒子在石墨烯表面分布均匀且粒径平均。与纯的TiO2相比,G-TiO2在紫外-可见吸收谱中的吸收边缘明显向可见光区域移动。G-TiO2的结构依赖于溶剂热反应的时间,适当延长反应时间可以有利于石墨烯与TiO2之间形成化学键,得到结合更好、分散更为均一的复合材料。石墨烯的引入可以有效阻止TiO2电子空穴对的复合,这可以用G-TiO2的荧光淬灭来证明。G-TiO2对亚甲基蓝的光催化降解活性还与原料中氧化石墨烯的含量有关,最佳制备条件下得到的G-TiO2,在模拟太阳光的照射下,3小时内可以催化降解超过75%的亚甲基蓝。本文还进行了部分类石墨烯材料的研究。在第五章中,利用液相法制备了二维MOS2片,探测到其与块状MoS2完全不同的荧光发射性质。通过引入Ag@SiO2核壳复合材料,利用金属增强荧光的机理可进一步提高二维MoS2的荧光强度。更多还原

【Abstract】 Graphene is the name given to a two-dimensional sheet of sp2-hybridized carbon, which can be seen as the basic building block of carbon allotropes. The 2D structure and long-rangeπconjugation of graphene bring unique thermal, mechanical and electrical properties. Therefore graphene exhibits significant potentials in both theoretical studies and practical applications. In this work, for solving the crucial problems existing in biosensors, graphene and Au nanoparticles were utilized to promote the electrons transportation and keep the activity of the enzyme to construct novel biosensors with high performance. Besides, graphene-based nanocomposites were successfully synthesized through solvothermal reaction by using graphene oxide and metal salt precursors as starting materials. The applications of the nanocomposites were also studied.Water soluble graphene was prepared chemically in chapter 2. First, we synthesized graphene oxide using a Hummers method and followed sonication in water. Before reduction with hydrazine, graphene oxide layers were sulfonated to modify the surface with sulfonate groups. The obtained graphene layers could keep separate in water through the electrostatic repulsion due to the presence of negatively charged -SO3- groups.The water soluble graphene was utilized to construct novel hydrogen peroxide biosensors and glucose biosensors respectively in chapter 3. (1) Graphene and horseradish peroxidase (HRP) were co-immobilized into biocompatible polymer chitosan. Then a glassy carbon electrode was modified by the biocomposite, followed by electrodeposition of Au nanoparticles on the surface of the modified electrode to fabricate a hydrogen peroxide biosensor. Cyclic voltammetry demonstrated that the direct electrochemistry of HRP was realized. This biosensor exhibited an excellent performance in terms of electrocatalytic reduction towards H2O2, with a response time of 3 s. The linear range to H2O2 was from 5×10-6 M to 5.13×10-3 M, and the detection limit was 1.7×10-6 M. (2) Graphene, Au nanoparticles and glucose oxidase were co-dispersed into a Nafion solution. Then the dispersion was cast on the surface of a glassy carbon electrode to construct a glucose biosensor. This biosensor responded rapidly upon the addition of glucose and reached the steady state current within 5 s, with the presence of hydroquinone. The linear range is from 15×10-6 M to 5.8×10-3 M, and the detection limit is approximate 5×10-6 M.In chapter 4, we studied the preparation of graphene-metal oxide composites through solvothermal reaction in one step by using graphene oxide and metal salts as starting materials. (1) Graphene-Fe3O4 composites (G-Fe3O4) were synthesized with solvothermal reaction by using graphene oxide and FeCl3 as raw materials. The oxygen groups were decomposed under the high temperature and high pressure inside the sealed vessel and graphene oxide was reduced into graphene, while the Fe3+ ions adsorbed on the surface of graphene were reduced and grown to Fe3O4 in situ. The size and density of the Fe3O4 microspheres distributed on the graphene can be easily controlled by altering the starting Fe3+ concentration. The saturation magnetization of the composites at room temperature was about 45.5 emu g-1. Considering the high specific surface area and good biocompatibility of graphene, the obtained G-Fe3O4 composites were very suitable for the immobilization and delivery of drugs. The saturated loading capacity of the composites to doxorubicin could achieve 65%. We also immobilized the G-Fe3O4 on the surface of an electrode to construct a H2O2 biosensor, which also displayed excellent performance. (2) Graphene-TiO2 composites (G-TiO2) were synthesized through solvothermal reaction by using graphene oxide and tetrabutyl titanate as raw materials. TiO2 particles of anatase phase with a narrow size distribution were dispersed on the surface of graphene uniformly. In comparison with pure TiO2, the G-TiO2 showed an obvious red shift of absorption edge in the UV-vis absorption spectra. The structure of the G-TiO2 composites depended on the time of solvothermal reaction. Prolonging the reaction time moderately could promote the chemical bonding of TiO2 on graphene, which was beneficial to obtain more homogeneous products. The fluorescence quenching of the G-TiO2 indicated that graphene could hinder the recombination of electron-hole pairs of TiO2. The photocatalytic activity of the G-TiO2 was also affected by the amount of graphene in the composites. Under the optimal conditions, more than 75% of methylene blue would be degraded in 3 hours by the photocatalysis of the G-TiO2 with the irradiation of a simulated sunlight.The investigation of the graphene analogues was also carried out in this work. Ultrathin MoS2 layers with few or even single layer were prepared with a liquid-phase exfoliation. The photoluminescence of the exfoliated MoS2 was detected, which was absent in bulk MoS2. And the intensity of the fluorescence could be further enhanced by using Ag@SiO2 composite as an enhancing substrate based on the metal-enhanced fluorescence mechanism.更多还原