【作者】 何光裕；

【导师】 汪信； 孙小强； 陈海群；

【作者基本信息】 南京理工大学 ， 材料科学与工程， 2013， 博士

【摘要】 石墨烯是近年来发现的碳基新材料,除了拥有大比表面积、高化学稳定性、较好吸附能力等诸多性能外,还具有更为优异的电学性质和规整的平面二维结构,这使其可以作为一个理想的载体担载各类无机化合物,非常适合于开发大规模、高性能石墨烯基纳米复合材料,是石墨烯迈向实际应用的一个重要方向。本文以制备高性能、低成本的石墨烯纳米复合材料为主要目的,采用不同的制备方法制备了多种无机化合物与石墨烯的复合材料,研究了复合物的形成机理和工艺影响因素,探索了复合物微观结构与其性能之间的关系,为深入探索石墨烯功能材料的形成机理以及构筑性能新颖的石墨烯碳纳米材料奠定基础。具体内容如下：(1)以天然石墨为原料制备了氧化石墨,通过控制水合肼用量得到了不同还原程度的稳定的石墨烯水分散液,并通过石墨烯片层自组装制备出高度有序的石墨烯薄膜。通过UV-Vis跟踪检测实现了对氧化石墨烯还原过程的有效控制,揭示了石墨烯还原程度与石墨烯薄膜性质的关系。石墨烯薄膜经高温热处理后,随着还原程度提高,其导电性随着也从0.51S·cm-1提高至61.32S·cm-1.薄膜拉伸强度随着还原程度提高而提高,杨氏模量与还原程度无关,当N2H4:GO(质量比)=0.2时,拉伸强度达到最大,为176.1MPa,此时杨氏模量亦达到最大,为35.1GPa。UV-Vis可以简便有效的监测和控制氧化石墨烯的还原程度,使大规模制备性能可控的石墨烯薄膜材料成为可能。(2)采用均匀沉淀法制备纳米ZnO粉体,再用Bi2O3对其进行掺杂改性,然后将其负载在石墨烯上制成ZnO-Bi2O3/石墨烯复合材料。以亚甲基蓝为目标污染物,对纳米ZnC、ZnO-Bi2O3、ZnO-Bi2O3/石墨烯的光催化性能进行比较。结果表明ZnO-Bi2O3/石墨烯复合材料对亚甲基蓝的光催化活性明显高于ZnO-Bi2O3,2h对亚甲基蓝的降解率在95%以上,石墨烯作为电子受体,光激发后的电子转移到石墨烯上,从而降低了光生电子与空穴的复合率,提高了光催化活性,该复合材料对酸性蓝、酸性黄、活性红等工业染料也有很好的光催化活性,同时具有较好的稳定性。(3)采用共沉淀法制得了对H202有极好活化能力的磁性四氧化三铁石墨烯复合材料,复合材料在H202体系中对酸性红RS的催化降解性能研究表明,由于Fe3O4/石墨烯可催化H202分解成活性很高的·OH,即使在碱性条件下对酸性红RS的降解率仍达到80%以上,在模拟太阳光照射条件下对阳离子染料亚甲基蓝的降解率高达99%,并且催化剂性能稳定,循环使用十次对染料的降解率仍可达到95%以上；同时,Fe3O4/石墨烯复合材料在水合肼还原硝基化合物方面具有很高的催化活性,使用3.1wt%的Fe3O4/石墨烯催化剂,3.6倍量的水合肼,反应18min,苯胺的收率可达99.2%,且催化剂具有用量少、活性高、易回收和稳定性好等优点。(4)通过水热法制备了三种钴基石墨烯复合材料并对其电化学性能进行了研究。制得的粒状CO3O4/石墨烯复合材料比电容高达562F·g-1,在0.1A·g-1的电流密度下,循环1000次比电容量仅仅衰减了2.6%；在此基础上用Ni对复合材料进行了掺杂改性,制得的线状NiCo2O4/石墨烯复合材料表现出高的比电容量(1A·g-1时为737F·g-1)和优异的循环稳定性(4000圈后～83%)；本文同时研究了石墨烯结构缺陷对复合材料性能的影响,通过将硝酸钴与超声制得的石墨烯分散液在水热条件下一步反应制得C0304/石墨烯基复合材料,在1A·g-1的电流密度下,复合材料的比电容高达384F·g-1,在充放电1000次后比电容仅损失2%。上述几种超级电容器材料均表现出较好的电化学电容性能和良好的循环稳定性。(5)通过湿法固相球磨硝酸银与石墨一步制得Ag/石墨烯复合材料,实现石墨烯剥离与银纳米粒子负载同步完成。石墨烯和银纳米颗粒的协同作用使其抗菌效果明显增强,其对E. coli和S. aureus的最小抑菌浓度分别为30μg·mL-1和60μg·mL-1,对细菌的杀灭率大于99.6%,多次循环使用后抗菌效果依旧很好；当Ag/石墨烯复合材料的浓度从10μg·mL-1上升到500μg·mL-1时,细胞存活率缓慢地下降,细胞呈现早期凋亡的轻微固缩的细胞核。实验结果显示制得的Ag/石墨烯复合材料具有良好的抑菌性能,优良的稳定性和浓度相关的生物相容性。更多还原

【Abstract】 Graphene, a novel carbon-based material, has been emerging in recent years, which possesses many distinctive properties, such as an extremely large specific surface area, high chemical stability, good adsorption ability, excellent electrical properties and regular two-dimensional structure. Due to these propertites, graphene can be used as an ideal substrate to load various types of inorganic substance for the large-scale fabrication of high-performance graphene-based nanocomposites, leading to the practical application of graphene. This dissertation aimed mainly at the preparation of graphene-based nanocomposites with high-performance at a low cost. A variety of graphene-based inorganic nanocomposites were prepared using different methods. The formation mechanism of those composites and the influence of technical factors of the preparation procedure were studied. The relations between the microstructure and the performance of the composites were explored, providing theoretical basis for further study of the formation mechanism of graphene-based functional materials and the construction of graphene-based nanomaterials with novel performance. The contents are as follows:(1) Graphite oxide was synthesized from natural graphite powder, and stable graphene suspensions with different reduction level were obtained by controlling the dosage of hydrazine. Graphene paper with a well-ordered structure was then fabricated by the self-assembly of graphene sheets. The formation of stable graphene dispersions with different reduction levels enabled the monitoring of GO reduction by UV-Vis spectroscopy, though which the relevance of the chemical reduction level to the properties of graphene paper was revealed. As the reduction level increased after being heat-treated, the conductivity of the graphene paper samples exhibited an increasing trend from0.51S·cm-1to61.32S·cm-1. Whilst the tensile strength increased with the reduction level, the changing trend of the stiffness of graphene paper samples is independent to the reduction level. However, when the molar ratio of N2H4to GO was1, the graphene paper sample yielded the greatest mean tensile strength of176.1MPa as well as the greatest mean Young’s modulus of35.1GPa. UV-Vis spectrometry was found to be a valid and facile method to monitor and control the reduction level of graphene oxide, which may pave the way for large scale fabrication of graphene-based nanomaterials.(2) The ZnO nanopowder was synthesized by homogeneous precipitation method then doped with Bi2O3, which was loaded onto the graphene (GE) substrate afterwards to fabricate nanocomposite. Take MB as a target pollutant, the photocatalytic performance of ZnO nanopowder, ZnO-Bi2O3and ZnO-Bi2I3/GE were systematically compared. It was found that the photocatalytic activity of ZnO-Bi2O3/GE was higher than ZnO-Bi2O3regarding the photodegradation of MB. The photodegradation of MB over ZnO-Bi2O3/GE reached95%after irradiation with visible light for2h. Photogenerated electrons transfered easily to graphene, the electron acceptor, decreasing the recombination of photogenerated electrons and holes thereby improving the photocatalytic performance. ZnO-Bi2O3/GE also showed high photocatalytic activity and good photocatalytic stability for the degradation of acid blue, acid yellow, reactive red, acid red, reactive yellow and reactive blue under visible light irradiation.(3) Magnetically separable Fe3O4/GE nanocomposite was prepared by a facile co-precipitation method, which exhibited excellent activation ability to H2O2. In the presence of H2O2, the catalytic activity of the Fe3O4/GE nanocomposites on the degradation of Acid Scarlet RS was studied. The degradation rate of Acid Scarlet RS aqueous solution was up to80%even under alkaline conditions since H2O2would decompose to highly activated OH radical by the catalysis of Fe3O4/GE. Under simulated sunlight irradiation, the degradation rate of MB aqueous solution reached to99%with a degradation rate of95%maintained after being recycled for ten times. Furthermore, the Fe3O4/GE composite showed efficient catalytic activity for the reduction of nitroarenes by hydrazine hydrate. In the reduction of nitrobenzene, the yield of the reduced product, aniline, reached up to99.2%after18min with3.1wt%of Fe3O4/GE composite being used as catalyst and hydrazine hydrate in a3.6:1molar ratio to nireobenzene being used as reductant. The Fe3O4/GE composite offered significant advantages such as low dosage of catalyst, high catalytic activity, easy recycling and excellent stability.(4) Three cobalt-based graphene composites were prepared by hydrothermal process and their electrochemical properties were studied in detail. The specific capacitance (Cs) of granular Co3O4-reduced GO (Co3O4-RGO) nanocomposite was as high as562F·g-1. The Cs decreased2.6%at a current density of0.1A·g-1after1000cycles. Based on that, the NiCo2O4nanowire/RGO composite was obtained by hybridizing Ni into it, which showed high Cs of737F·g-1at a current density of1A·g-1and only17%loss of the initial specific capacitance after4000charge/discharge cycles. The effect of the structural defect of graphene on the performance of the composite was also investigated. Co3O4/GE nanocomposite was prepared using Co(NO3)2and the ultrasonically exfoliated graphene through a hydrothermal route. Galvanostatic charge/discharge experiments on Co3O4/GE showed high Cs of384F·g-1at a large current density of lA·g-1. Furthermore, the Cs decreased only2%of initial capacitance after1000cycles, indicating the enhanced stability of the Co3O4nanoparticles during the electrochemical process. The above mentioned graphene-based composites all exhibited excellent electrochemical capacitive performance and good cycling stability.(5) Ag/graphene antibacterial composite was prepared by one-pot wet ball-milling of AgNO3and graphite, in which the loading of Ag nanoparticles and the exfoliation of graphene were achieved simultaneously. The Ag/graphene composite provided enhanced antibacterial performance due to the synergistic effect between the silver nanoparticles and graphene. Ag/GNS showed good antibacterial activity against both E. coli and S. aureus. The minimum inhibitory concentration (MIC) was30μg·mL-1and60μg·mL-1, respectively, and more than99.6%of bacteria was killed. It was found that the Ag/GNS maintained a high antibacterial activity after being recycled. Cytotoxicity test showed that with the concentration of Ag/GNS increasing from10to500μg·mL-1, the cell viability declined slowly. The early apoptotic cells exhibited bright blue nuclei and weakly condensed chromatin. Experiment results indicated that the obtained Ag/GNS composite possessed enhanced antibacterial activity, outstanding stability and a concentration dependent cytotoxicity.更多还原