【作者】 徐超；

【导师】 汪信；

【作者基本信息】 南京理工大学 ， 材料科学与工程， 2010， 博士

【摘要】 石墨烯,一种由单层碳原子紧密堆积成的二维蜂窝状晶格结构碳质材料,至2004年发现以来,已在实验科学和理论科学上受到了极大的关注。由于其具有特殊的纳米结构以及优异的性能,基于石墨烯的材料已在电子学、光学、磁学、生物医学、催化、传感器、储能等诸多领域显示出了巨大的应用潜能。本论文中,将主要以化学修饰后的石墨烯-氧化石墨烯为前驱体,制备了基于石墨烯的衍生物及复合物材料,并对部分产物的性能进行了表征；同时也对石墨烯材料在粒子合成过程中的特殊功能进行了考察。主要内容如下：1.氧化石墨烯的表面改性。利用含有两个异氰酸酯基团的甲苯2,4-二异氰酸酯作为桥联剂将具有双亲功能的高分子接枝到氧化石墨烯的表面,从而获得了具双亲功能的氧化石墨烯。改性后的石墨烯能够同时在水和有机溶剂中稳定地分散。2.石墨烯的制备。以还原性较弱的乙醇和乙二醇为还原剂,分别利用醇热法和多元醇还原法,实现了对氧化石墨烯的选择性还原。经过乙醇和乙二醇处理后的氧化石墨烯,只有环氧基功能团可以被还原,而对羟基和羧基的还原效果则比较差。由于只是部分还原,氧化石墨烯的石墨化程度比水合肼还原的要低,因而醇还原后的石墨烯所具有的导电率介于氧化石墨烯和深度还原后的氧化石墨烯之间。3.基于石墨烯的纳米粒子复合物（1）在有机溶剂正己醇中,通过硝酸钴盐在氧化石墨烯表面原位分解成核形成Co₃O₄粒子,从而获得了氧化石墨烯-CO₃O₄复合物。由于可能结合了氧化石墨烯和CO₃O₄两种组分对高氯酸铵的催化热分解作用,氧化石墨烯-CO₃O₄复合物的添加不仅降低了高氯酸铵的热分解温度,同时也提高了其放热量。（2）以氧化石墨烯为前驱体,采用了水-乙二醇混合体系,制备了石墨烯-贵金属纳米粒子（Au, Pt, Pd）复合物。在反应体系中,金属纳米粒子被乙二醇还原并吸附在氧化石墨烯的表面,然后作为催化剂,在较低的温度下催化乙二醇还原氧化石墨烯,从而最终得到石墨烯负载金属纳米粒子复合物。以石墨烯-Pt复合物为模板,利用循环伏安法考察了该复合物在甲醇燃料电池上的应用。结果显示了石墨烯-Pt复合物对甲醇具有很好的催化活性,且具有很好的抗中毒性和循环寿命。（3）采用了醇热法制备了石墨烯负载TiO2纳米粒子的复合物。在160℃反应温度下,钛酸四丁酯可以分解形成TiO2纳米粒子,并且负载在醇还原的石墨烯单片上,从而形成石墨烯-TiO2纳米粒子复合物。通过改变反应过程中钛酸四丁酯的用量,还可以调节负载在石墨烯表面的TiO2纳米粒子的量,获得不同石墨烯与TiO2配比的复合材料。4.以氧化石墨烯为纳米衬底,采用了银镜反应制备了准二维的银纳米粒子膜。通过该方法制备的二维银纳米粒子膜具有很好的灵活性,能够在水中分散形成稳定的悬浮液。将这种稳定悬浮的银纳米粒子膜进行堆砌组装,可以形成具有镜面反射性质的连续的宏观粒子膜。这类纳米粒子膜具有拉曼增强性能,使吸附在银粒子膜上的氧化石墨烯的拉曼信号有着明显增强,并且信号增强的程度可以通过控制银纳米粒子的密度进行调节。5.石墨烯材料在粒子合成过程中的特殊功能（1）以预吸附乙酸铜的氧化石墨烯为原料,采用多元醇还原的方法制备了石墨烯-Cu₂O复合物。结果显示,在氧化石墨烯存在的条件下,Cu₂O可以形成边长在200nm左右立方块形颗粒。而没有加入氧化石墨烯时,所形成的Cu₂O则为团聚的、没有固定形貌的纳米粒子。这一结果说明了石墨烯在Cu₂O合成的过程中,起到了特殊的模板作用,使得Cu₂O粒子的生长具有一定的方向性,从而形成了立方块形。此外,锂电池电化学性质的初步测试结果显示了该复合物第一次的充放电循环具有较大的储存容量,但该电极材料的循环性却比较差。（2）利用改进的银镜反应研究了氧化石墨烯对银纳米粒子大小的影响。结果证明,氧化石墨的加入可以明显降低所合成银粒子的大小,并且反应前的预热时间、反应的温度、银盐的用量、氧化石墨烯的用量等条件对最终形成的银纳米粒子的大小都有一定的影响。在一定条件下利用氧化石墨烯稳定的银纳米粒子具有非常好的稳定性,能够与一些有机溶剂如甲醇、乙醇、丙酮、异丙醇任意的混合而仍然保持很好的稳定分散。更多还原

【Abstract】 Graphene, a monolayer of carbon atoms packed into a dense honeycomb crystal structure, has attracted tremendous attention from both the experimental and theoretical scientific communities since it was found in 2004. Due to the unique nanostructure and extraordinary properties, graphene based materials have shown promising applications in electronics, optics, magnetics, biomedicine, catalysis, sensors, energy storage etc. In this dissertation, the chemical modified graphene-graphene oxide was used as precursor to prepare graphene based derivants and composites, and certain properties of these products were also analyzed. Furthermore, the special functions of graphene based sheets on synthesis of particles were also investigated. The dissertation is mainly focused on:1. Surface modification of graphene oxide. Amphiphilic oligoester was grafted onto the surface of graphene oxide after utilization of toluene-2,4-diisocyanate as a coupling agent, which contained two isocyanate groups. One remarkable result after modification was that the obtained graphene was dispersed stably in both aqueous and organic solutions.2. Preparation of graphene. Graphene oxide was selective reduced using ethanol and ethylene glycol as reductants through solvothermal and polyol methods, respectively. Only the epoxy groups on graphene oxides were reduced by alcohols, while those groups such as hydroxyl and carboxyl groups were maintained. Due to the partial reduction, the degree of re-graphitization of alcohol reduced graphene oxide was lower than that of hydrazine reduced, and the conductivity also fell into an intermediate stage between that of graphene oxide and its deeply reduced counterparts.3. Graphene based nanoparticle composites.（1） Graphene oxide-Co₃O₄ nanocomposites were synthesized through the in situ decomposition of cobalt nitrate and crystal growth of CO3_O4 on the surface of graphene oxide sheets in n-hexanol solvent. Probably due to the concert effect of graphene oxide and CO₃O₄ on the catalysis of ammonium perchlorate, the addition of graphene oxide-Co₃O₄ composites not only brought down the decomposition temperature, but also increased the exothermic heat of ammonium perchlorate.（2） Graphene-metal nanoparticle （Au, Pt and Pd） composites were synthesized using graphene oxide sheets as precursor and metal nanoparticles as building blocks in the water-ethylene glycol system. In this system, the metal nanoparticles formed first and were adsorbed onto the surface of carbon sheets. Then these particles played a pivotal role in catalytic reduction of graphene oxide with ethylene glycol under low temperature, leading to the formation of graphene-metal particle nanocomposites consequently. The graphene-Pt composite was used as a model to test the applicability in direct methanol fuel cells through cyclic voltammograms analyses. And results indicated that such composite possessed good catalysis activity and cyclability.（3） Graphene-TiO₂ composites were prepared using solvothermal progress. At 160℃, the tetrabutyl titanate decomposed into TiO₂ nanoparticles and adsorbed onto the alcohol reduced graphene sheets, forming composite consequently. The densities of TiO₂ nanoparticles on graphene sheets were altered easily just through controlling the usage of tetrabutyl titanate.4. Graphene oxide sheets had been used as the nanoscale substrates for the formation of quasi-two-dimensional silver nanoparticle films. These silver nanoparticle films assembled on graphene oxide sheets were flexible and formed stable suspensions in aqueous solutions. And the obtained suspensions were easily processed into macroscopic films with high reflectivity. Raman signals of graphene oxide in such hybrid films were increased by the attached silver nanoparticles and the degree of enhancement could be adjusted by varying the quantity of silver nanoparticles on the graphene oxide sheets.5. The special functions of graphene-based sheets on the particle synthesis.（1） Graphene-cuprous oxide （CU₂O） composites were prepared using copper acetate pre-adsorbed graphene oxide sheets as precursors. Results showed that cubic CU₂O particles with an edge length of～200 nm formed in the present of graphene oxide, while ruleless and hard aggregated CU₂O particles were obtained without graphene oxide. Such results indicated that in our system the carbon sheets might play a role as a template which made Cu₂O crystals grow along certain directions, forming cube-like crystals. A preliminary study on the electrochemical behavior of the graphene-Cu₂O composite used as anode material for lithium ion batteries was carried out. The capacity of such sample was high in the first charge-discharge cycle. Nevertheless, such electrode showed a poor cyclability.（2） A modified silver mirror reaction was used to investigate the affection of graphene oxide on the silver particle size. Results confirmed that addition of graphene oxide could lead to forming small silver nanoparticles. Meanwhile, the reaction conditions such as pre-heated time, temperature, the usage of silver salt and graphene oxide also affected the size of silver nanoparticles. Under certain conditions, the as-synthesized aqueous silver particle colloids were much stable, which were mixed discretionarily with some organic solvents, such as methanol, ethanol, acetone,1-propanol. etc.. and kept stability.更多还原