石墨烯的制备与表征综述

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石墨烯的制备及其在铅酸电池中的应用

石墨烯的制备及其在铅酸电池中的应用

石墨烯的制备及其在铅酸电池中的应用石沫;杨新新;周明明;吴亮;柯娃;李厚训;戴贵平【摘要】添加炭材料能够明显地提高铅酸电池的性能。

石墨烯是具有独特平面二维结构的炭材料,具有很多优异的性能,如良好的导电性和很高的比表面积。

本文综述了石墨烯的制备方法,并对目前石墨烯在铅酸电池中的应用情况进行了研究和总结。

%Carbon materials can significantly improve the performance of lead-acid batteries. Graphene is a kind of carbon materials with unique two-dimensional structure, which has a lot of excellent performance, such as good electrical conductivity and high speciifc surface area. This paper reviews the preparation methods of graphene, and its application in lead-acid batteries.【期刊名称】《蓄电池》【年(卷),期】2015(000)003【总页数】4页(P142-145)【关键词】炭材料;石墨烯;导电性;铅酸电池【作者】石沫;杨新新;周明明;吴亮;柯娃;李厚训;戴贵平【作者单位】超威电源有限公司研究院,浙江湖州313100;超威电源有限公司研究院,浙江湖州313100;超威电源有限公司研究院,浙江湖州313100;超威电源有限公司研究院,浙江湖州313100;超威电源有限公司研究院,浙江湖州313100;超威电源有限公司研究院,浙江湖州313100;超威电源有限公司研究院,浙江湖州313100【正文语种】中文【中图分类】TM912.1石墨烯是碳原子紧密堆积的二维蜂窝状晶格结构的碳质材料,碳原子排列呈平面六边形结构,在二维平面上每个碳原子以 sp2杂化轨道相连接[1]。

氧化石墨烯的制备及表征

氧化石墨烯的制备及表征

氧化石墨烯的制备及表征文献综述材料0802班李琳200822046氧化石墨烯的制备及表征李琳摘要:石墨烯(又称单层石墨或二维石墨)是单原子厚度的二维碳原子晶体,被认为是富勒烯、碳纳米管和石墨的基本结构单元[1]。

石墨烯可通过膨胀石墨经过超声剥离或球磨处理来制备[2,3],其片层厚度一般只能达到30~100 nm,难以得到单层石墨烯(约0.34 nm),并且不容易重复操作。

所以寻求一种新的、容易和可以重复操作的实验方法是目前石墨烯研究的热点。

而将石墨氧化变成氧化石墨,再在超声条件下容易得到单层的氧化石墨溶液,再通过化学还原获得,已成为石墨烯制备的有效途径[4]。

通过述评氧化石墨及氧化石墨烯的制备、结构、改性及其与聚合物的复合,展望了石墨烯及其复合材料的研究前景。

关键词:氧化石墨烯,石墨烯,氧化石墨,制备,表征Oxidation of graphite surfaces preparation and CharacterizationLI LinAbstrat:Graphite surfaces (also called single graphite or 2 d graphite )is the single atoms thickness of the 2 d carbon atoms crystal, is considered fullerenes, carbon nanotubes and graphite basic structure unit [1].Graphite surfaces can through the expanded graphite after ultrasonic stripping or ball mill treatment topreparation [2,3], a piece of layer thickness normally only up to 30 to 100 nm, hard to get the single graphite surfaces (about 0.34 nm), and not easy to repeated operation. So to search a new, easy to operate and can be repeated the experiment method of the graphite surfaces is the focus of research. And will graphite oxidization into oxidation graphite, again in ultrasonic conditions to get the oxidation of the single graphite solution, again through chemical reduction get, has become an effective way of the preparation of graphite surfaces [4]. Through the review of graphite oxide and oxidation graphite surfaces of the preparation, structure, modification of polymer and thecompound, and prospects the graphite surfaces and the research prospect of composite materials.Key words:Oxidation graphite surfaces, graphite surfaces, oxidation graphite, preparation,characterization采用Hummers 方法[5]制备氧化石墨。

综述制备石墨烯的化学方法

综述制备石墨烯的化学方法
Solid-state 13C NMR spectroscopy of graphite oxide and recently of 13C-labelled graphite oxide favours the model shown in Fig. 1a; the sp2-bonded carbon network of graphite is strongly disrupted and a significant fraction of this carbon network is bonded to hydroxyl groups or participates in epoxide groups29–32. Minor components of carboxylic or carbonyl groups are thought to populate the edges of the layers in graphite oxide. This indicates that further work with solid-state NMR on 13C-labelled graphite oxide is necessary, along with (for example) titration with fluorescent tags of carboxylic and other groups to identify their spatial distribution on individual graphene oxide platelets derived from graphite oxide as discussed further below.
The development of various methods for producing graphene — a single layer of carbon atoms bonded together in a hexagonal lattice — has stimulated a vast amount of research in recent years1. The remarkable properties of graphene reported so far include high values of its Young’s modulus (~1,100 GPa)2, fracture strength (125 GPa)2, thermal conductivity (~5,000 W m−1K−1)3, mobility of charge carriers (200,000 cm2 V−1 s−1)4 and specific surface area (calculated value, 2,630 m2 g−1)5, plus fascinating transport phenomena such as the quantum Hall effect6. Graphene and chemically modified graphene (CMG) are promising candidates as components in applications such as energy-storage materials5, ‘paper-like’ mater­ials7,8, polymer composites9,10, liquid crystal devices11 and mechanical resonators12.

综述石墨烯的制备与应用

综述石墨烯的制备与应用

半导体物理课程作业石墨烯的制备与应用(材料)目录一、石墨烯概述 (2)二、石磨烯的制备 (3)1、机械剥离法 (3)2、外延生长法 (5)3、化学气相沉积法 (6)4、氧化石墨-还原法 (6)5、电弧法 (9)6、电化学还原法 (9)7、有机合成法 (10)三、石墨烯的应用 (11)1、石墨烯在电子器件领域的应用 (11)1.1 石墨烯场效应晶体管 (11)1.2 石墨烯基计算机芯片 (12)1.3 石墨烯信息存储器件 (13)2、石墨烯在能源领域的应用 (14)2.1 石墨烯超级电容器 (14)2.2 锂离子电池 (15)2.3 太阳能电池 (16)2.4 储氢/甲烷器件 (17)3、石墨烯在材料领域的应用 (18)3.1 特氟龙材料替代物 (18)3.2 石墨烯聚合物复合材料 (18)3.3 光电功能材料 (19)4、石墨烯在生物医药领域的应用 (20)4.1 基于氧化石墨烯的纳米载药体系 (20)4.2 氧化石墨烯对DNA/基因/蛋白的选择性检测 (21)4.3用于生物成像技术 (23)4.4 石墨烯在肿瘤治疗方面的应用 (23)四、总结及展望 (24)参考文献 (25)一、石墨烯概述碳广泛存在于自然界中,是构成生命有机体的基本元素之一。

碳基材料是材料界中一类非常具有魅力的物质,从无定形的碳黑到晶体结构的天然层状石墨;从零维纳米结构富勒烯到一维碳纳米管无不给人们带来炫丽多彩的科学新思路。

而二维碳基材料石墨烯的发现,不仅极大地丰富了碳材料的家族,而且其所具有的特殊纳米结构和性能,使得石墨烯无论是在理论还是实验研究方面都已展示出了重大的科学意义和应用价值,从而为碳基材料的研究提供新的目标和方向。

碳的晶体结构—石墨和金刚石(三维)是自然界中最早为人们熟知的两种碳同素异构体,因化学成键方式不同而具有截然相反的特性。

1985年,一种被称为“巴基(零维)被首次发现,三位发现者于11年后, 即1996年获诺贝尔球”的足球形分子C60化学奖。

石墨烯复合材料的制备、性能与应用

石墨烯复合材料的制备、性能与应用

石墨烯复合材料的制备、性能与应用摘要:纳米科学技术是当今社会科学中一个重要的研究话题。

它是现代科学技术的重要内容,也是未来技术的主流。

是基础研究与应用探索紧密联系的新兴高尖端科学技术。

石墨烯具有独特的结构和优异的电学、热学、力学等性能,自从2004年被成功制备出来,一直是全世界范围内的一个研究热点。

由于石墨烯具有巨大的表面体积比和独特的高导电性等特性,石墨烯及其复合材料在电化学领域中有着诱人的应用前景,因此,石墨烯材料的制备及其在电化学领域应用的研究是石墨烯材料研究的一个重要领域。

综述了石墨烯与石墨烯复合材料的制备及其在超级电容器、锂离子电池、太阳能电池、燃料电池等电化学领域中应用的研究现状,展望了石墨烯材料的制备及其在电化学领域应用的未来发展前景。

关键词;复合材料纳米材料石墨烯正文;一,石墨烯复合材料的制备石墨烯是2004年才被发现的一种新型二维平面复合材料,其特殊的单原子层决定了它具有丰富而新奇的物理性质。

研究表明,石墨烯具有优良的电学性质,力学性能及可加工性。

石墨烯复合材料的制备是石墨烯研究领域的一个重要的课题,如何简单,快速,绿色地制备其复合材料,而又采用化学分散法大量制备氧化石墨烯,并采用直接共混法制备氧化石墨烯/酚醛树脂纳米复合材料。

通过AFM、SEM、FT-IR、TG等对其进行表征,结果表明,氧化石墨烯完全剥离,并在基体中分散均匀,而且两者界面相容性好,提高了复合材料的热稳定性。

通过高温热处理使复合材料薄膜在兼顾形貌的同时实现导电,当氧化石墨烯含量为2%(质量分数)时,其导电率为96.23S/cm。

采用原位乳液聚合和化学还原法制备了石墨烯和聚丙乙烯的复合材料。

研究表明PS微球通过公家方式连接到石墨烯的表面。

通过PS微球修饰后的石墨烯在氯仿中变现良好的分散性。

制备的复合材料具有优良的导电性,同时PS的玻璃化温度的热稳定性得到了提高。

本研究所提出的方法具有环境友好高效的特点,渴望被采用到其他聚合物和化合物来修饰石墨烯。

石墨烯的制备方法

石墨烯的制备方法

一.文献综述随着社会的发展,人们对材料的要求越来越高,碳元素在地球上分布广泛,其独特的物理性质和多种多样的形态己逐渐被人类发现、认识并利用。

1924年确定了石墨和金刚石的结构;1985年发现了富勒烯;1991年发现了碳纳米管;2004年,曼彻斯特大学Geim等成功制备的石墨烯是继碳纳米管被发现后富勒烯家族中又一纳米级功能性材料,它的发现使碳材料领域更为充实,形成了从零维、一维、二维到三维的富勒烯、碳纳米管、石墨烯以及金刚石和石墨的完整系统。

而2004年至今,关于氧化石墨烯和石墨烯的研究报道如雨后春笋般涌现,其已成为物理、化学、材料学领域的国际热点课题。

制备石墨烯的方法有很多种,如外延生长法,氧化石墨还原法,CVD法,剥离-再嵌入-扩涨法以及有机合成法等。

在本文中主要介绍氧化石墨还原法。

除此之外,还对其的一些性能进行表征。

二.石墨烯材料2.1石墨烯材料的结构和特征石墨烯(gr即hene)是指碳原子之间呈六角环形排列的一种片状体,由一层碳原子构成,可在二维空间无限延伸,可以说是严格意义上的二维结构材料,同时,它被认为是宇宙上最薄的材料[`2],也被认为是有史以来见过的最结实的材料。

ZD结构的石墨烯具有优异的电子特性,且导电性依赖于片层的形状和片层数,据悉石墨烯是目前已知的导电性能最出色的材料,可运用于导电高分子复合材料,这也使其在微电子领域、半导体材料、晶体管和电池等方面极具应用潜力。

有专家指出,如果用石墨烯制造微型晶体管将能够大幅度提升计算机的运算速度,其传输电流的速度比电脑芯片里的硅元素快100倍。

近日,某科技日报称,mM的研究人员展示了由石墨烯材料制作而成的场效应晶体管(FET),经测试,其截止频率可达100吉赫兹(GHz),这是迄今为止运行速度最快的射频石墨烯晶体管。

石墨烯的导热性能也很突出,且优于碳纳米管。

石墨烯的表面积很大,McAlliste:等通过理论计算得出石墨烯单片层的表面积为2630扩/g,这个数据是活性炭的2倍多,可用于水净化系统。

石墨烯的制备及电化学性能研究

石墨烯的制备及电化学性能研究

目录摘要 (I)Abstract ......................................................................................................................... I I 1 引言 (1)1.1 石墨烯的制备 (2)1.1.1 机械剥离法 (2)1.1.2 电化学剥离法 (2)1.1.3 化学气相沉积法 (3)1.2 石墨烯电极材料的制备 (5)1.3 石墨烯电极材料电化学性能测试 (5)2 实验部分 (6)2.1 实验试剂 (6)2.2 实验仪器 (6)2.3 RHAC和GQDs的制备 (6)2.4 RHAC-GQDs的制备 (6)2.5 电极制备和电池组装 (7)3 结果和讨论 (8)3.1 分析了RHAC的比表面积和孔隙结构 (8)3.2 GQDs的拉曼光谱和荧光光谱分析 (8)3.3 红外光谱分析 (8)3.4 XRD分析 (8)3.5 扫描电镜分析 (9)3.6 循环伏安法测试分析 (9)3.7 恒流充放电试验分析 (9)3.8 电化学阻抗分析 (10)4 结论与展望 (12)4.1 结论 (12)4.2 主要创新点 (12)4.3 展望 (12)参考文献 (13)致谢............................................................................................ 错误!未定义书签。

摘要石墨烯由于其十分优异的电学、热学和机械性能及优良的透光率、比表面积大等优势而广泛的受到人们追捧。

尤其是在2004年成功制得稳定存在的石墨烯之后,更是兴起了一股研究石墨烯的潮流。

如何成本低廉、面积大、数量丰富、质量优异的制备石墨烯,并将其应用在实际生产中是研究人员努力的目标。

本文主要对这几年中一些改善的或新的石墨烯的制备方法以及其电化学性能做了综述,从中可以看到石墨烯在电学方面存在巨大的发展潜力。

石墨烯的研究与应用综述、产业现状

石墨烯的研究与应用综述、产业现状

石墨烯的研究与应用综述一、石墨烯的结构与特性石墨烯是碳原子紧密堆积成单层二维蜂窝状晶格结构的一种碳质新材料,是最薄的二维材料,单层的厚度仅0.335nm。

石墨烯可塑性极大,是构建其他维数碳材料的基本单元,可以包裹成零维的富勒烯结构,卷曲成一维的碳纳米管,以及堆垛成三维的石墨等。

石墨烯的理论研究已有60多年的历史,但直至2004年,英国曼彻斯特大学物理学家安德烈·海姆和康斯坦丁·诺沃肖洛夫,利用胶带剥离高定向石墨的方法获得真正能够独立存在的二维石墨烯晶体,二人因此荣获2010年诺贝尔物理学奖。

石墨烯具有一些奇特的物理特性:导电性极强:石墨烯中的电子没有质量,电子的运动速度能够达到光速的1/300,是世界上电阻率最小的材料。

良好的导热性:石墨烯的导热性能优于碳纳米管和金刚石,单层石墨烯的导热系数可达5300瓦/米水度,远高于金属中导热系数高的银、铜等。

极好的透光性:石墨烯几乎是完全透明的,只吸收2.3%的光,并使所有光谱的光均匀地通过。

超高强度:石墨烯被证明是当代最牢固的材料,硬度比莫氏硬度10级的金刚石还高,却又拥有很好的韧性,可以弯曲。

超大比表面积:石墨烯拥有超大的比表面积(单位质量物料所具有的总面积),这使得石墨烯成为潜力巨大的储能材料。

石墨烯特殊的结构形态,具备目前世界上最硬、最薄的特征,同时具有很强的韧性、导电性和导热性,这些极端特性使其拥有巨大发展空间,应用于电子、航天、光学、储能、生物医药、日常生活等大量领域。

二、石墨烯的制备方法石墨烯的制备方法主要有机械法和化学法2种。

机械法包括微机械分离法、取向附生法和加热碳化硅法;化学法包括外延生长法、化学气相沉积法与氧化石墨还原法。

微机械分离法是直接将石墨烯薄片从较大的晶体上剪裁下来,可获得高品质石墨烯,且成本低,但缺点是石墨烯薄片尺寸不易控制,不适合量产;取向附生法是利用生长基质原子结构“种”出石墨烯,石墨烯性能令人满意,但往往厚度不均匀;加热碳化硅法能可控地制备出单层或多层石墨烯,是一种新颖、对实现石墨烯的实际应用非常重要的制备方法,但制备大面积具有单一厚度的石墨烯比较困难。

石墨烯论文总结范文

石墨烯论文总结范文

摘要:石墨烯作为一种新型二维材料,具有独特的物理化学性质,在众多领域展现出巨大的应用潜力。

本文对石墨烯的制备方法、特性、应用领域进行了综述,旨在为石墨烯材料的研究提供参考。

一、引言石墨烯是一种由单层碳原子构成的二维晶体,具有优异的力学、电学、热学和光学性能。

自2004年石墨烯被发现以来,其研究取得了显著的进展。

本文对石墨烯的制备方法、特性、应用领域进行综述,以期为石墨烯材料的研究提供参考。

二、石墨烯的制备方法1. 机械剥离法:机械剥离法是制备石墨烯的一种简单、高效的方法。

通过将石墨片在金刚石针尖下进行机械剥离,可以得到单层石墨烯。

2. 化学气相沉积法:化学气相沉积法是一种制备高质量石墨烯的方法。

该方法在高温下将碳源气体在金属催化剂上分解,形成石墨烯。

3. 水热法:水热法是一种制备石墨烯的新技术。

通过将石墨烯前驱体在高温高压下进行反应,可以得到高质量的石墨烯。

4. 微机械剥离法:微机械剥离法是一种基于微机械加工技术制备石墨烯的方法。

通过在石墨烯上施加应力,使其发生剥离,从而获得单层石墨烯。

三、石墨烯的特性1. 优异的力学性能:石墨烯具有极高的强度和韧性,是已知材料中最强的二维材料。

2. 良好的电学性能:石墨烯具有优异的电导率,是已知材料中最高的二维材料。

3. 热学性能:石墨烯具有优异的热导率,可以有效传递热量。

4. 光学性能:石墨烯具有优异的光吸收和光催化性能。

四、石墨烯的应用领域1. 电子器件:石墨烯具有优异的电学性能,可以应用于制备高性能电子器件,如场效应晶体管、晶体管等。

2. 能源存储与转换:石墨烯具有良好的电化学性能,可以应用于锂离子电池、超级电容器等能源存储与转换领域。

3. 光学器件:石墨烯具有优异的光学性能,可以应用于制备高性能光学器件,如光子晶体、光学传感器等。

4. 生物医学领域:石墨烯具有良好的生物相容性,可以应用于生物医学领域,如药物载体、生物传感器等。

五、结论石墨烯作为一种新型二维材料,具有独特的物理化学性质,在众多领域展现出巨大的应用潜力。

氧化还原法制备石墨烯的方法概述分析

氧化还原法制备石墨烯的方法概述分析

毕业论文题目:氧化还原法制备石墨烯的方法概述学院:专业:毕业年限:学生姓名:学号:指导教师:目录摘要 (2)关键词 (2)Abstract (2)Key words (2)I前言 (3)Ⅱ氧化还原法制备石墨烯 (3)2.1氧化石墨(GO)的制备 (4)2.1.1Brodie法 (5)2.1.2Staudenmaier法 (6)2.1.3Hummers法 (6)2.2氧化石墨(GO)的还原 (6)2.2.1热还原法 (6)2.2.2溶剂热还原 (7)2.2.3光照还原. (7)2.2.4化学液相还原 (7)Ш展望 (9)参考文献 (10)致谢 (13)氧化还原法制备石墨烯的方法概述摘要:近年来 , 石墨烯以其独特的结构和优异的性能, 在化学、物理和材料学界引起了广泛的研究兴趣。

人们已经在石墨烯的制备方面取得了积极的进展, 为石墨烯的基础研究和应用开发提供了原料保障。

本文大量引用近年来最新参考文献 , 综述了用氧化还原法制备石墨烯,并对它的发展前景进行了展望!关键词:氧化石墨,石墨烯 , 氧化还原法The Summarize of oxidation-reduction method for grapheneShaoqing Ma , Zhongai Hu(Northwest normal university, chemical engineering college, lanzhou, 730070)Abstract :In recent years, graphene with its unique structure and the outstanding performance, caused wide interests in the chemical, physical and material fields. People have made positive progress in the preparation of graphene,and have provided raw material guarantee for graphene of basic research and application development. This paper largely applied the latest references in recent years , reviewed the legal system with oxidation-reduction method for graphene and presented the development prospects.Key words : graphite oxide, graphene, oxidation-reduction methodI前言Partoens 等[1]研究发现 , 当石墨层的层数少于 10 层时 , 就会表现出较普通三维石墨不同的电子结构。

石墨烯简介

石墨烯简介

readme tiansen :石墨烯应用部分前五个可以适当删除。

1综述石墨烯2石墨烯的制备方法3石墨烯的特性一、石墨烯简介1、石墨烯定义石墨烯(Graphene)是从石墨材料中剥离出来、由碳原子组成的只有一层原子厚度的二维晶体。

2004年,英国曼彻斯特大学物理学家安德烈·盖姆和康斯坦丁·诺沃肖洛夫,成功从石墨中分离出石墨烯,证实它可以单独存在,两人也因此共同获得2010年诺贝尔物理学奖。

2、石墨烯研究历史实际上石墨烯本来就存在于自然界,只是难以剥离出单层结构。

石墨烯一层层叠起来就是石墨,厚1毫米的石墨大约包含300万层石墨烯。

铅笔在纸上轻轻划过,留下的痕迹就可能是几层甚至仅仅一层石墨烯。

石墨烯在实验室中是在2004年,当时,英国曼彻斯特大学的两位科学家安德烈·杰姆和克斯特亚·诺沃消洛夫发现他们能用一种非常简单的方法得到越来越薄的石墨薄片。

他们从高定向热解石墨中剥离出石墨片,然后将薄片的两面粘在一种特殊的胶带上,撕开胶带,就能把石墨片一分为二。

不断地这样操作,于是薄片越来越薄,最后,他们得到了仅由一层碳原子构成的薄片,这就是石墨烯。

这以后,制备石墨烯的新方法层出不穷,经过5年的发展,人们发现,将石墨烯带入工业化生产的领域已为时不远了。

因此,在随后三年内, 安德烈·盖姆和康斯坦丁·诺沃肖洛夫在单层和双层石墨烯体系中分别发现了整数量子霍尔效应及常温条件下的量子霍尔效应,他们也因此获得2010年度诺贝尔物理学奖。

在发现石墨烯以前,大多数物理学家认为,热力学涨落不允许任何二维晶体在有限温度下存在。

所以,它的发现立即震撼了凝聚体物理学学术界。

虽然理论和实验界都认为完美的二维结构无法在非绝对零度稳定存在,但是单层石墨烯在实验中被制备出来。

石墨烯是富勒烯(0维)、碳纳米管(1维)、石墨(3维)的基本组成单元,可以被视为无限大的芳香族分子。

二、制备方法1、撕胶带法发现石墨烯使用的方法2、机械剥离法是利用物体与石墨烯之间的摩擦和相对运动,得到石墨烯薄层材料的方法。

德国应用化学--石墨烯综述

德国应用化学--石墨烯综述

DOI:10.1002/anie.200901678Graphene:The New Two-Dimensional NanomaterialC.N.R.Rao,*A.K.Sood,K.S.Subrahmanyam,and indarajAngewandteChemieKeywords:carbon ·graphene ·graphene oxide ·monolayers ·nanostructures77522009Wiley-VCH Verlag GmbH &Co.KGaA,WeinheimAngew.Chem.Int.Ed.2009,48,7752–77771.IntroductionGraphene,the parent of all graphitic forms (Figure 1),has become one of the most exciting topics of research in the last three to four years.[1]This two-dimensional material consti-tutes a new nanocarbon comprising layers of carbon atoms arranged in six-membered rings.It is distinctly different from carbon nanotubes (CNTs)and fullerenes,and exhibits unique properties which have fascinated the scientific community.Typically important properties of graphene are a quantum Hall effect at room temperature,[2–4]an ambipolar electric field effect along with ballistic conduction of charge carriers,[5]tunable band gap,[6]and high elasticity.[7]Although graphene is expected to be perfectly flat,ripples occur because of thermal fluctuations.[1]Ideally graphene is a single-layer material,but graphene samples with two or more layers are being investigated with equal interest.Three different types of graphenes can be defined:single-layer graphene (SG),bilayer graphene (BG),and few-layer graphene (FG,number of layers 10).Although single-layer graphene and bilayer graphene were first obtained by micro-mechanical cleavage,[5]several strategies have since been developed for the synthesis of graphenes.[8]Graphene has been characterized by a variety of micro-scopic and other physical techniques including atomic force microscopy (AFM),transmission electron microscopy (TEM),scanning tunneling microscopy (STM),X-ray dif-fraction (XRD),and Raman spectroscopy.[1]It is interesting that single-layer graphene placed on a silicon wafer with a 300nm thick layer of SiO 2,becomes visible in an optical microscope (Figure 2a and b).[8–10]While AFM directly gives the number of layers (Figure 2c),[8]STM (Figure 2d)[11]and TEM (Figure 2e)[12]images are useful in determining the morphology and structure of graphene.Raman spectroscopy has emerged to be an important tool for the characterization of graphene samples.[13–16]Herein,we shall discuss various aspects of graphene,including synthesis,structure,properties,functionalization,and polymer composites.Although we have covered most of the important facets of graphene published up to May 2009,we have given somewhat greater importance to the chemical aspects and cited a large number of references from the rapidly increasing literature.We do hope that the[*]Prof.Dr.C.N.R.Rao,K.S.Subrahmanyam,indarajInternational Centre for Materials Science,New Chemistry Unit and CSIR Centre of Excellence in Chemistry,Jawaharlal Nehru Centre for Advanced Scientific ResearchJakkur P.O.,Bangalore 560064(India)Fax:(+91)80-2208-2760E-mail:cnrrao@jncasr.ac.in Prof.Dr.A.K.SoodDepartment of Physics,Indian Institute of Science Bangalore 560012(India)E very few years,a new material with unique properties emerges andfascinates the scientific community,typical recent examples being high-temperature superconductors and carbon nanotubes.Graphene is the latest sensation with unusual properties,such as half-integer quantum Hall effect and ballistic electron transport.This two-dimen-sional material which is the parent of all graphitic carbon forms is strictly expected to comprise a single layer,but there is considerable interest in investigating two-layer and few-layer graphenes as well.Synthesis and characterization of graphenes pose challenges,but there has been considerable progress in the last year or so.Herein,wepresent the status of graphene research which includes aspects related to synthesis,characterization,structure,and properties.From the Contents1.Introduction 77532.Synthesis77543.Electronic Structure 77604.Phonons and Raman Spectroscopy 77625.Effects of Doping 77646.Functionalization and Solubilization 77677.Decoration with Metal and Metal Oxide Nanoparticles 77698.Properties77709.Polymer Composites 777310.Outlook7773Figure 1.Graphene:the parent of all graphitic forms.(From Ref.[1a].)7753Angew.Chem.Int.Ed.2009,48,7752–77772009Wiley-VCH Verlag GmbH &Co.KGaA,Weinheimreferences are sufficiently representative and will help the reader to obtain more detailed information.2.Synthesis2.1.Single-Layer GrapheneSingle-layer graphene has been generally prepared by micromechanical cleavage in which highly oriented pyrolitic graphite(HOPG)is pealed using scotch-tape and deposited on to a silicon substrate.Besides mechanical cleavage of graphite,the other important methods employed to produce graphene samples are epitaxial growth on an insulator surface (such as SiC),chemical vapor deposition(CVD)on the surfaces of single crystals of metals(e.g.,Ni),arc discharge of graphite under suitable conditions,use of intercalated graph-ite as the starting material,preparation of appropriate colloidal suspensions in selected solvents,and reduction of graphene oxide sheets.[8]By employing mechanical exfoliation of graphite,mono-layers and bilayers of graphene with minimum lateral dimensions of2–10nm can be deposited onto the Si(100)-2 1:H surface.[17]Room-temperature ultrahigh vacuum scan-ning tunneling spectroscopy has been used to characterize the nanometer-sized single-layer graphene to reveal a size-dependent energy gap ranging from0.1to1eV.By correlat-ing resolved tunneling spectroscope and atomically resolved images,the dependence of the electronic structure of single-layer graphene on lateral size,edge structure,and crystallo-graphic orientation has been examined.Single-and few-layer graphenes taken from freshly cleaved HOPG surfaces by the scotch-tape technique can be readily transferred on to a given substrate using electrostatic deposition.[18]While mechanical cleavage of graphene layers from a graphite crystal has afforded the study of the properties of single-layer graphene or bilayer graphene,the method is not suitable for large scale synthesis of single-layer graphene or of few-layer graphene(FG).Among the methods and proce-dures for large-scale synthesis two categories should be distinguished:a)those which start with graphite or a com-parable starting material not containing any oxygenfunction-C.N.R.Rao obtained his PhD degree fromPurdue University(1958)and DSc degreefrom the University of Mysore(1961).He isthe National Research Professor and LinusPauling Research Professor at the JawaharlalNehru Centre for Advanced ScientificResearch and Honorary Professor at theIndian Institute of Science(both at Banga-lore).His research interests are mainlyinthe chemistry of materials.He is the recipi-ent of the Einstein Gold Medal of theUNESCO,the Hughes Medal of the RoyalSociety,and the Somiya Award of theInternational Union of Materials Research Societies(IUMRS).In2005,hereceived the Dan David Prize for materials research and the first IndiaScience Prize.A.K.Sood is a Professor of Physics at theIndian Institute of Science,Bangalore.He isa member of the science academies of Indiaand has received various medals and hon-ours in physics including the BhatnagarPrize and the TWAS Prize.His main inter-ests are soft condensed matter,nanomateri-als,and light scattering.K.S.Subrahmanyam received his MSc(Chemistry)degree from University ofHyderabad in2006.He is a student of PhDprogramme in the Jawaharlal Nehru Centrefor Advanced Scientific Research,Bangaloreand received his MS(Engg.)degree in2008.He is working on synthesis and character-ization of graphenes.indaraj obtained his PhD degreefrom University of Mysore and is a SeniorScientific Officer at the Indian Institute ofScience,and Honorary Faculty Fellow at theJawaharlal Nehru Centre for Advanced Sci-entific Research.He works on different typesof nanomaterials.He has authored morethan100research papers and co-authored abook on nanotubes and nanowires.Figure2.Microscopy images of graphene crystallites on300nm SiO2imaged with a)white and b)green light.Figure(b)shows step-likechanges in the contrast for single-,bi-,and trilayer graphenes.c)AFMimage of single-layer graphene.The folded edge exhibits a relativeheight of approximately4 indicating that it is single-layer.d)High-resolution STM image.e)TEM images of folded edges of single-andbilayer graphenes.(From Refs.[9,11,12b].) 2009Wiley-VCH Verlag GmbH&Co.KGaA,Weinheim Angew.Chem.Int.Ed.2009,48,7752–7777alities and b)those which involve the exfoliation of graphite oxide (GO)followed by reduction.The latter methods yield sheets of reduced graphite oxide,some of which could be single-layer materials.Reduced graphite oxide layers are to be considered as chemically modified graphenes since they generally contain some oxygen functions,such as OH or COOH groups.Under category (a),some of the methods are growth on SiC surfaces,hydrogen arc discharge,conversion of nanodiamond,CVD on metal surfaces,and dispersion of graphite in solvents.Large-area single-layer graphene has been prepared by thermal decomposition of the (0001)face of a 6H-SiC wafer under ultrahigh vacuum (UHV)conditions.[19]Single-layer graphene has been grown on top of a 6H-SiC (0001)substrate by an ex situ method,which gives larger mono-layer graph-enes in comparison with an in situ method (Figure 3).[20a]Thus,ex situ graphitization of Si-terminated SiC (0001)in an argon atmosphere of 1bar yields monolayer films with large domain sizes.[20b]Temperature-dependent structural changes of graphene layers on the 6H-SiC(0001)surface studied by photoelectron spectroscopy,low-energy electron diffraction,and extended X-ray absorption spectroscopy (EXAFS)indicate that a bilayer-like graphene sheet is formed after annealing at 11508C.The tilting angle of the graphene sheet is estimated to be 14Æ28.As the number of the graphene layers increases,the angle gradually decreases to 7Æ28at 14008C.[20c]Graphene suspensions can be readily produced by dis-persing graphite in surfactant–water solutions.[21a]Individual sheets on HOPG have been manipulated by scanning probe microscope (SPM)tips,but it is more reliable to first pattern the HOPG surface to create an array of small graphite islands by reactive ion etching with an oxygen plasma.[21b]Exfoliation of lithium-intercalated multiwalled carbon nanotubes yields single-layer graphene flakes.[22a]Gram quantities of single-layer graphene have been prepared by employing a solvothermal procedure and sub-sequent by sonication.[23]In this process,thesolvothermalFigure 3.a)Low-energy electron microscope (LEEM)image of a single-domain single-layer graphene grown ex situ on the (0001)surface of SiC;the field of view is 20m m wide and the electron energy isE vac +4.4eV.b)LEEM image showing the existence of two domains of monolayer graphene.c)Photoelectron intensity map versus binding energy and parallel momentum showing the electronic structure close to the Dirac point at the K point of the Brillouin zone.(From Ref.[20a].)Figure 4.a,b)High-resolution TEM images of a)solution-cast monolayer and b)solution-cast bilayer graphenes (scale bar 500nm).c)Electron diffraction pattern of the monolayer in (a).d,e)Electron diffraction patterns taken from the positions of the d)black and e)white spots,respectively,of the sheet in (b).The graphene is one-layer thick in (d)and a bilayer in (e).f–h)Diffracted intensity taken along the 1À210to À2110axis for the patterns in (c–e).i)Histogram of the ratios of the intensity of the {1100}and {2110}diffraction peaks.A ratio >1is a signature of graphene.(From Ref.[24].)7755Angew.Chem.Int.Ed.2009,48,7752–77772009Wiley-VCH Verlag GmbH &Co.KGaA,Weinheimproduct of sodium and ethanol is subjected to low-temper-ature flash pyrolysis yielding a fused array of graphene sheets,which are dispersed by mild sonication.Single-layer graphene can be produced in good yields by solution-phase exfoliation of graphite in an organic solvent,such as N -methylpyrroli-done (NMP)(Figure 4).[24]This process works because the energy required to exfoliate graphene is balanced by the solvent–graphene interaction.Exfoliation of alkali-metal intercalated graphite in NMP yields a stable solution of negatively charged graphene sheets which can be deposited on substrates.[25]Two-dimensional linear graphene ribbons can be prepared chemically by the oxidative cyclodehydroge-nation of polyphenylene precursors.[26]Highly conducting graphene sheets produced by the exfoliation–reintercalation–expansion of graphite are readily suspended in organic solvents.[27]The sheets in organic solvents can be made into large,transparent,conducting films by Langmuir–Blodgett assembly in a layer-by-layer manner.The initial step is exfoliation of the commercial expandable graphite (160–50N,Grafguard)by brief (60s)heating to 10008C in forming gas (i.e.hydrogen and nitrogen),followed by reintercalation by oleum (fuming sulfuric acid with 20%free SO 3),and insertion of tetrabutylammonium hydroxide (TBA,40%solution in water)into the oleum-intercalated graphite in DMF.TBA-inserted oleum-interca-lated graphite is sonicated in a DMF solution of 1,2-distearoyl-sn -glycero-3-phosphoethanolamine-N -[methoxy-(polyethyleneglycol)-5000](DSPE-mPEG)for 60min to obtain a homogeneous suspension.This method gives large amounts of graphene sheets which can be transferred to other solvents including water and organic solvents (Figure 5).The average size of the single-layer graphene sheet was 250nm and the average topographic height was approximately 1nm.Graphitic oxide,obtained by the oxidation of graphite,contains a considerable amount of surface oxygen in the form of OH and COOH groups.Mechanical or thermal exfoliation graphitic oxide gives single-layer graphene oxide (SGO).Single-layer graphene oxide on reduction by hydro-gen,hydrazine or other reducing agents gives single-layer graphene.Single-layer graphene has been prepared on a large scale by a solution-based approach,involving the dispersion of graphitic oxide in pure hydrazine.Hydrazine-basedcolloids are deposited on different substrates to obtain chemically modified graphene sheets with large areas (20 40m m;Figure 6).[29a]Schniepp et al.[29b]have shown that exfoliation of graphitic oxide yields single-layer graphene oxide through the expansion of CO 2evolved in the space between the sheets during rapid heating (Figure 7).A detailed analysis of the thermal-expansion mechanism of graphitic oxide to produce single-layer graphene sheets has been described.[29c]Chemically modified graphenes have been produced in different ways.These include hydrazinereduc-Figure 5.a)Schematic representation of the exfoliated graphite reinter-calated with sulphuric acid molecules (spheres)between the layers.b)Schematic of tetrabutyl ammoniumhydroxide (TBA;dark blue spheres)in the intercalated graphite.c)Schematic of single-layer graphene coated with DSPE–mPEG molecules also shown is a photo-graph of the solution of single-layer graphene.d)AFM image of asingle-layer graphene with a topographic height of approximately 1nm (scale bar:300nm.e)Low-magnification TEM image of a single-layer graphene that is several hundred nanometres in size (scale bar:100nm).f)Electron diffraction pattern of a single-layer graphene as in (e).(From Ref.[27].)Figure 6.Photographs of chemically converted graphene suspensions.a)graphite oxide paper in a glass vial and b)the graphite oxide dispersion after addition of hydrazine.Below the vials,three-dimensional computer-generated molecular models of graphene oxide (C gray,O red,H white)and the reduced graphene are shown.Removal of -OH and -COOH groups by reduction gives the planar structure.c)SEM and d)AFM images of a chemically converted graphene sheet on Si/SiO 2substrate.(From Ref.[29a].)2009Wiley-VCH Verlag GmbH &Co.KGaA,Weinheim Angew.Chem.Int.Ed.2009,48,7752–7777tion of the colloidal suspension of single-layer graphene oxide in DMF/water [28a]or in water.[28b]Electrostatic stabilization enables stable aqueous dispersions of the single-layer graph-ene sheets.2.2.Graphenes with One to Three LayersThe dispersion behavior of graphene oxide in different organic solvents,such as DMF,NMP ,ethylene glycol and tetrahydrofuran (THF)has been studied.[30]As-prepared graphite oxide formed by the Hummers method undergoes full exfoliation into single-layer graphene oxide under sonication forming stable dispersions in the above solvents.The sample prepared from the dispersion in DMF yields sheets of uniform thickness (1.0–1.4nm).Single-layer and bi-layer graphene sheets are obtained by using a substrate-free,atmospheric-pressure microwave plasma reactor,wherein liquid ethanol droplets are passed through an argon plasma (Figure 8).[31]High-quality graphene sheets of 1–3layers have been synthesized on stainless steel substrates at 5008C bymicrowave plasma chemical vapor deposition (CVD)in an atmosphere of 10%methane and 90%hydrogen at a pressure of 30torr and a flow rate of 200sccm (standard cubic centimeter per minute).[32]Arc-discharge of graphite in hydrogen appears to yield primarily two-and three-layer graphenes (see next section).2.3.Few-Layer GraphenesStarting with graphite and by employing chemical exfo-liation,high-quality graphene with a predetermined number of layers can be obtained.[33]With artificial graphite,flake graphite powder,Kish graphite,and natural flake graphite as starting materials,nearly 80%of the final product has been found to be single-layer,single-and double-layer,double-and triple-layer,and few-layer (4–10layers)graphene respec-tively.A mixture of few-layer (4–10layers)graphene and thick graphene (>10layers)is obtained when HOPG is used (Figure 9).Large-scale transfer of mono and few-layer graphenes from SiO 2/Si,to any type of substratematerialFigure 7.a)Tapping-mode AFM image (8m m 8m m)showing an individual thermally exfoliated graphite oxide flakes.b)Pseudo-3D representa-tion of a 600nm 600nm AFM scan of an individual graphene sheet showing the wrinkled,rough surface.c)Contact-mode AFM scan of adifferent flake,providing an accurate thickness of the sheet.Inset:atomic-scale image of the HOPG lattice.d)Cross-section of an unwrinkled area in (b)(position indicated by black dashed line in (b)).e)Histogram showing the narrow distribution of sheet heights.f)Cross-section through the sheet in (c)showing a height minimum of 1.1nm.(From Ref.[29b].)7757Angew.Chem.Int.Ed.2009,48,7752–77772009Wiley-VCH Verlag GmbH &Co.KGaA,Weinheimhas been carried out.During the transferring process no morphological changes or corrugations are induced (Figure 10).[34]Well-ordered graphite films with a thickness of a few graphene layers have been grown on nickel substrates by CVD from a mixture of hydrogen and methane activated by a direct current (DC)discharge.[35]These films contain atomically smooth micron-size regions separated from each other by ridges.The film thickness is (1.5Æ0.5)nm.An arc-discharge method involving evaporation of graph-ite electrodes in a hydrogen atmosphere has been reported forpreparing graphene flakes.[36a]The presence of H 2during the arc-discharge process terminates the dangling carbon bonds with hydrogen and prevents the formation of closed struc-tures,[37–38]such as rolling of sheets into nanotubes and graphitic polyhedral particles.This method is useful to prepare boron-and nitrogen-doped graphene.To prepare pure graphene (HG),direct current arc evaporation of graphite was carried out in a water-cooled stainless steel chamber filled with a mixture of hydrogen and helium in different proportions,without using a catalyst.The propor-tions of H 2and He used in our experiments are,H 2(70torr)/He (500torr),H 2(100torr)/He (500torr),H 2(200torr)/He (500torr),and H 2(400torr)/He (300torr).In a typical experiment,the discharge current was in the 100–150A range,with a maximum open circuit voltage of 60V .[39]The arc was maintained by continuously translating the cathode to keep a constant distance of 2mm from the anode.The arc discharge deposit formed on the inner walls of the reaction chamber was examined to characterize the graphene (Figure 11).The deposit mainly contained graphenes with 2–4layers and the areas were in the 10–40 103nm 2range.Hydrogen arc discharge of graphitic oxide has also been employed to produce graphene sheets.[36b]Using microwave plasma-enhanced CVD,under a flow of a methane/hydrogen mixture,micrometer-wide flakes con-sisting of few-layer graphene sheets (four to six atomic layers)have been prepared on quartz and silicon by the controlled recombination of carbon radicals in the microwave plasma.[40]Continuous large-area films of single-to few-layer graphene have been grown on polycrystalline Ni films by ambient-pressure CVD using methane/hydrogen feed gas andtrans-Figure 9.Tapping-mode AFM images and the height profiles of graphenes derived from a),d)kish graphite,b),e)flake graphitepowder,and c),f)artifical graphite.The thickness of the graphenes are 1.9–2.3nm,1.3–2.1nm,and 1.1–1.3nm respectively.(From Ref.[33].)Figure 8.Synthesis of graphene sheets:a)Schematic representation of the atmospheric-pressure microwave plasma reactor.b)Photograph of graphene sheets dispersed in methanol.c)TEM image of graphene sheets suspended on a carbon TEM grid.Homogeneous and feature-less regions (indicated by arrows)indicate areas of single-layer graphene;Scale bar:100nm.(From Ref.[31].)Figure 10.a)Schematic representation of the transferring process.Graphene sheets are deposited on SiO 2/Si substrates via HOPGmicrocleaving and then transferred to a nonspecific substrate.b,c)Op-tical images of macroscopic regions having graphite and graphene flakes on b)the original substrate and c)the SiO 2/Si substrates.Arrows point to PMMA residues.(From Ref.[34].)2009Wiley-VCH Verlag GmbH &Co.KGaA,WeinheimAngew.Chem.Int.Ed.2009,48,7752–7777ferred on to substrates assisted by poly(methyl methacrylate)wet etching (Figure 12).[41]Highly crystalline graphene rib-bons (<20–30m m in length)with widths of 20–300nm and a small thickness (2–40layers)have been synthesized by aerosol pyrolysis using a mixture of ferrocene,thiophene,and ethanol.[42]A microwave plasma enhanced CVD strategy,also called a substrate-lift-up approach,has been used for the efficient synthesis of multilayer graphene nanoflake films on Si substrates without the use of metal catalysts.[43]Single-and few-layer graphene films exhibiting electrical characteristics somewhat similar to bilayer graphene have been deposited onto Si/SiO 2substrates starting from graphitic oxide.[44]Stable dispersions of graphitic oxide in a mixture of water and a non-aqueous solvent such as DMF,methanol,or acetone,are spray deposited on a pre-heated substrate,subsequent chemical reduction yields non-agglomerated graphene sheets.Stable aqueous dispersions of single to few-layer graphene sheets have been prepared using a water soluble pyrene derivative (1-pyrenebutyrate)as the stabilizer and hydrazine monohydrate as the reducing agent.[45]Since the pyrene moiety has strong affinity (because of p -stacking)with the basal plane of graphite,the flexible graphene sheets become non-covalently functionalized.Few-layer graphene nanosheets can also be produced by a soft chemistry route involving graphite oxidation,ultrasonic exfoliation,and chemical reduction by refluxing with hydroquinone.[46]Chemical vapor deposition using camphor (camphor graphene;CG),conversion of nanodiamond (nanodiamond graphene;DG)and thermal exfoliation of graphitic oxide (exfolitated graphitic oxide graphene;EG)produce few-layer graphenes in large quantities.[47]In the first method,camphor is pyrolysed over nickel nanoparticles at 7708C in the presence of argon.[48]The method to prepare DG involves annealing nanodiamond at 16508C or higher in a helium atmosphere.[49]It is generally found that the surface areas vary as EG >DG >HG.The number of layers is smallest (2–4)in rge and flat graphene flakes having single to few layers have been produced from HOPG by an initial epoxy bonding process followed by reverse exfoliation.[50]Kim et al [51a]have carried out large-scale growth of graphene films by CVD on thin nickel layers (<300nm)deposited on SiO 2/Si substra-tes.[51a]These workers also describe two methods of patterning the films and transferring them on to substrates (Figure 13).The reaction of CH 4/H 2/Ar is carried out at 10008C.13C labeled graphene has been prepared by CVD of 13CH 4over nickel foil.[51b]Layer-by-layer growth of graphene on Ru-(0001)has been accomplished by temperature annealing of the metal containing interstitial carbon atoms [51c,d]Films of giant graphene molecules such as C 42H 18and C 96H 30have been processed through soft-landing mass spectroscopy.[51e]Preparation and characterization of graphene oxide paper,a free-standing carbon-based membrane material made by flow-directed assembly of individual graphene oxide sheets has been reported (Figure 14).[52]In this proce-dure,graphite oxide synthesized by the Hummers method was dispersed in water as individual graphene oxide sheets and the graphene oxide paper was made by filtration of the resulting colloid through an Anodisc membrane filter (47mm diame-ter,0.2m m pore size;Whatman),followed by air drying and peeling from the filter.While the exact procedures for large-scale synthesis of graphenes,specially single-layer graphene and few-layer graphene (with a relatively small number of layers, 6)have not been established,the most popular method appears to be one based on graphite oxide.Graphite oxide itself is prepared by treating graphite with a mixture of concentrated nitric acid,concentrated sulfuric acid,and potassium chlorate at room temperature for five days.[53]Exfoliation is carried out by giving a sudden thermal shock to graphitic oxide in a long quartz tube at 10508C under an argon atmosphere.[23]A stable suspension can be prepared by heating an exfoliated graphite oxide suspension under strongly alkaline conditions at moderate temperatures (50–908C).[54]Chemical reduction of exfoliated graphite oxide by reducing agents,such ashydra-Figure 11.a,b)High resolution TEM images of graphene (HG)pre-pared by the arc-discharge method (inset in (b)shows clearly a bi-layer graphene).c)AFM images and height profiles (1–2layers).(From Ref.[36a].)Figure 12.a)Optical image of a prepatterned nickel film on SiO 2/Si.CVD graphene is grown on the surface of the nickel pattern.b)Optical image of the grown graphene transferred from the nickel surface in panel (a)to another SiO 2/Si substrate.(From Ref.[41].)7759Angew.Chem.Int.Ed.2009,48,7752–77772009Wiley-VCH Verlag GmbH &Co.KGaA,Weinheimzine and dimethylhydrazine appears to be the promising strategy for the large-scale production of graphene.[55–56]Refluxing graphene oxide in hydrazine or even better,treating graphene oxide with hydrazine in a microwave oven,ensures reduction and produces aggregates of one-to-few (2–3)layer graphenes.Sonication and dispersion in a solvent,such as NMP ,favors the formation of a single-layer material.Reduction of graphene oxide with hydrazine is effectively carried out by first coating it with a surfactant,such as sodium dodecylbenzene sulfonate.[55–57]Reaction of the reduced species (coated with the surfactant)with an aryl diazonium salt gives the surfactant-wrapped chemically modified graphene which is readily dispersed in DMF or NMP .Reduced graphene oxide sheets dispersed in organic solvents can also be generated by taking graphite oxide up in an organic phase through the use of an amphiphile,and subsequent reduction with NaBH 4.[57]3.Electronic StructureThe graphene honeycomb lattice is composed of twoequivalent carbon sublattices A and B,shown in Figure 15a.Figure 15b shows the first Brillouin zone of graphene,with the high-symmetry points M,K,K ’,and G marked.Note that K and K ’are the two inequivalent points in the Brillouin zone.The s,p x and p y orbitals of carbon atoms form s bonds with the neighboring carbon atoms.The p electrons in the p z orbital,one from each carbon,form the bonding p and anti-bonding p *bands of graphene.The dispersion relation of these p electrons is described by the tight-binding model incorporating only the first nearest neighbor interactions [Eq.(1)][58–59]Figure 14.a–d)Digital camera images of graphene oxide paper:a)approximately 1m m thick;b)folded approximately 5m m thick semi-transparent film;c)folded approximately 25m m thick strip;d)strip after fracture from tensile loading.e–g)Low-,middle-,and high-resolution SEM side-view images of an approximately 10m m thick sample.(From Ref.[52].)Figure 13.Transfer processes for large-scale graphene films.a)Gra-phene film (centimetre-scale)grown on a Ni (300nm)/SiO2(300nm)/Si substrate,b)after etching the nickel layers in 1m FeCl 3aqueous solution.c)Graphene films having different shapes can be synthesized on top of patterned nickel layers.d,e)The dry-transfer method using a polydimethylsiloxane (PDMS)stamp is useful in transferring the patterned graphene films.d)the graphene film on the PDMS sub-strate,e)the underlying nickel layer is etched away using FeCl 3solution.f)Transparent and flexible graphene films on the PDMS substrates.g,h)The PDMS stamp makes conformal contact with a SiO 2substrate.Peeling back the stamp (g)leaves the film on a SiO 2substrate (h).(From Ref.[51a].)Figure 15.a)Graphene lattice.~a 1and ~a 2are the unit vectors.b)Recip-rocal lattice of graphene.The shaded hexagon is the first Brillouin zone.~b 1and ~b 2are reciprocal lattice vectors.2009Wiley-VCH Verlag GmbH &Co.KGaA,WeinheimAngew.Chem.Int.Ed.2009,48,7752–7777。

石墨烯的制备方法及应用

石墨烯的制备方法及应用

石墨烯的制备方法及应用无机光电0901 3090707020 黄飞飞摘要:石墨烯具有非凡的物理性质,如高比表面积、高导电性、高机械强度、易于修饰及大规模生产等。

2004年石墨烯的成功剥离,使石墨烯成为形成纳米尺寸晶体管和电路的“后硅时代”的新潜力材料,其产品研发和应用目前正在全球范围内急剧增加,本文通过对石墨烯特性、制备方法、在光电器件方面的应用几方面进行了综述,希望对石墨烯的综合应用进展有所了解。

关键词:石墨烯制备方法应用1 引言人们常见的石墨是由一层层以蜂窝状有序排列的平面碳原子堆叠而形成的,石墨的层间作用力较弱,很容易互相剥离,形成薄薄的石墨片。

当把石墨片剥成单层之后,这种只有一个碳原子厚度的单层就是石墨烯。

石墨烯(Graphene)的理论研究已有 60 多年的历史。

石墨烯一直被认为是假设性的结构,无法单独稳定存在,直至 2004 年,英国曼彻斯特大学物理学家安德烈·海姆和康斯坦丁·诺沃肖洛夫,成功地在实验中从石墨中分离出石墨烯,而证实它可以单独存在,两人也因在二维石墨烯材料的开创性实验而共同获得2010年诺贝尔物理学奖。

石墨烯的出现在科学界激起了巨大的波澜,从2006年开始,研究论文急剧增加,作为形成纳米尺寸晶体管和电路的“后硅时代”的新潜力材料,旨在应用石墨烯的研发也在全球范围内急剧增加,美国、韩国,中国等国家的研究尤其活跃。

石墨烯或将成为可实现高速晶体管、高灵敏度传感器、激光器、触摸面板、蓄电池及高效太阳能电池等多种新一代器件的核心材料。

2 石墨烯的基本特性至今为止,已发现石墨烯具有非凡的物理及电学性质,如高比表面积、高导电性、机械强度高、易于修饰及大规模生产等。

石墨烯是零带隙半导体,有着独特的载流子特性,为相对论力学现象的研究提供了一条重要途径;电子在石墨烯中传输的阻力很小,在亚微米距离移动时没有散射,具有很好的电子传输性质;石墨烯韧性好,有实验表明,它们每 100nm 距离上承受的最大压力可达 2.9 N,是迄今为止发现的力学性能最好的材料之一。

TMDs综述

TMDs综述

二维过渡金属硫族化合物及在光电子器件中的应用曾为材料学院西北工业大学2014100322摘要:由单层过渡金属硫族化合物(Transition metal dichalcogenides,TMDCs)构成的类石墨烯材料是一种新型二维层状化合物,近年来以其独特的物理、化学性质而成为新兴的研究热点。

本文综述了近年来二维TMDCs常见的几种制备方法,包括以微机械力剥离、锂离子插层和液相超声法等为主的“自上而下”的剥离法,以及以高温热分解、化学气相沉积等为主的“自下而上”的合成法;介绍了其常用的结构表征方法,包括原子力显微镜(AFM)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)和拉曼光谱等;概述了二维TMDCs的紫外-可见(UV-Vis)吸收、荧光发射等基本光物理性质及其相关机理;总结了二维TMDCs在二次电池、场效应晶体管、传感器、有机电致发光二极管和电存储等光电子器件领域的应用原理及其研究进展,展望了这类新型二维层状化合物的研究前景。

关键词:过渡金属硫族化合物;层状化合物;材料制备;结构表征;光物理性质;光电子器件Two-dimensional transition metal chalcogenides and applications in electronics and optoelectronics devicesAbstract: Two-dimensional(2D) Transition metal dichalcogenides (TMDCs), which is composed of a monolayer of TMDCs, is a new two-dimensional layered material that has attracted considerable attention recently because of its unique structure and optical and electronic properties. Here we first review the methods used to synthesize 2D TMDCs.“Top-down” methods include micromechanical exfoliation, lithium-based intercalation and liquid exfoliation, while the“bottom-up”approaches covered are thermal decomposition and hydrothermal synthesis. We then discuss several methods used to characterize the 2D TMDCs, such as atomic force microscopy (AFM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Raman spectroscopy. We describe the UV-Vis absorption and photoluminescent properties of 2D TMDCs and their related mechanisms. Finally, we summarize the application of 2D TMDCs in various optoelectronic devices such as secondary batteries, field-effect transistors, sensors. The application principles and research progress are discussed, followed by a summary and outlook for the research of thisemerging 2D layered nanomaterial.Key Words: Transition metal dichalcogenides; 2D layered material; Material synthesis; Structure characterization; Photophysical property; Optoelectronic device1 引言近年来随着石墨烯等二维层状纳米材料研究热潮的兴起[1-3],一类新型的二维层状化合物——过渡金属硫族化合物(Transition metal dichalcogenides,TMDCs) 引起了物理、化学、材料、电子等众多领域研究人员的广泛关注。

石墨烯综述

石墨烯综述

石墨烯综述1.1石墨烯概述石墨烯(Graphene)作为一种平面无机纳米材料,在物理、化学、科技、数码方面的发展都是极具前景的。

它的出现为科学界带来极大的贡献,机械强度高,导热和导电功能极具优势,原材料来源即石墨也相当丰富,是制造聚合复合物的最佳无机纳米技术。

由于石墨烯的运用很广泛,导致在工业界的发展存在很严重的一个问题就是其制作过程规模浩大,所以应该将其合理地分散到相应的聚合物内部,达到均匀分布的效果,同时平衡聚合物之间的作用力。

石墨烯的内部结构是以碳原子以sp 2杂化而成的,是一种单原子结构的平面晶体,其以碳原子为核心的蜂窝状结构。

一个碳原子相应的只与非σ键以外的三个碳原子按照相应的顺序连接,而其他的π则相应的与其他的的碳原子的π电子有机地组成构成离域大π键,在这个离域范围内,电子的移动不受限制,因为此特性使得石墨烯导电性能优异。

另一方面,这样的蜂窝状结构也是其他碳材料的基础构成元素。

如图1-1 所示,单原子层的最外层石墨烯覆盖组成零维的富勒烯,任何形状的石墨烯均可以变化形成壁垒状的管状[1]。

因为在力学规律上,受限于二维晶体的波动性,所以任何状态的石墨烯都不是平整存在的,而是稍有褶皱,不论是沉积在最底层的还是不收区域限制的。

,如图1-2 所示,蒙特卡洛模拟(KMC)做出了相应的验证[3]。

上面所提的褶皱范围在横向和纵向上都存在差异,这种微观褶皱的存在会在一定程度上引起静电,所以单层的会很容易聚集起来。

同时,褶皱的程度也会相应的影响其光电性能[3-6]图1-1. 石墨烯:其他石墨结构碳材料的基本构造单元,可包裹形成零维富勒烯,卷曲形成一维碳纳米管,也可堆叠形成三维的石墨[7]。


Figure 1-1. Graphene: the building material for other graphitic carbon materials. It can be wrapped up into 0D buckyballs, rolled into 1D nanotubes or stacked into 3D graphite[7].图 1-2. 单层石墨烯的典型构象[1]。

石墨烯增强尼龙6纤维的研究

石墨烯增强尼龙6纤维的研究

石墨烯增强尼龙6纤维的研究一、本文概述随着科技的不断进步和新型材料的持续研发,石墨烯作为一种新兴的碳纳米材料,在多个领域都展现出了其独特的优势和应用潜力。

特别是当石墨烯与尼龙6纤维结合时,形成的石墨烯增强尼龙6纤维,不仅在力学性能、热稳定性、导电性等方面有所提升,还进一步拓宽了尼龙6纤维的应用范围。

本文旨在深入探讨石墨烯增强尼龙6纤维的制备工艺、性能表征以及潜在应用,以期为相关领域的研究和发展提供有益的参考和借鉴。

本文将首先介绍石墨烯和尼龙6纤维的基本特性,阐述二者结合的必要性和可能性。

接着,重点介绍石墨烯增强尼龙6纤维的制备方法,包括溶液共混法、熔融共混法、原位聚合法等,并对比分析各种方法的优缺点。

随后,通过对石墨烯增强尼龙6纤维的力学性能、热稳定性、导电性等方面的测试和分析,全面评估其性能表现。

还将探讨石墨烯增强尼龙6纤维在航空航天、汽车制造、电子信息、体育用品等领域的应用前景。

本文还将对石墨烯增强尼龙6纤维的研究现状进行总结,分析其面临的挑战和未来的发展趋势,以期为推动该领域的研究和发展提供有益的启示和思考。

二、石墨烯的制备与表征石墨烯,一种由单层碳原子紧密排列形成的二维蜂窝状结构的纳米材料,因其优异的物理、化学和机械性能,在复合材料领域具有广泛的应用前景。

为了充分理解石墨烯对尼龙6纤维的增强效果,本研究首先对其制备和表征进行了详细探讨。

石墨烯的制备采用化学气相沉积法(CVD)。

在反应炉中放入镍箔作为催化剂,然后通入甲烷和氢气作为反应气体。

在高温下,甲烷分解的碳原子在镍箔表面形成单层石墨烯。

随着反应的进行,石墨烯在镍箔表面逐渐生长,形成连续且均匀的石墨烯薄膜。

待反应完成后,通过化学刻蚀法将石墨烯从镍箔上分离,得到自由悬浮的石墨烯。

为了确认石墨烯的形貌和结构,本研究采用了多种表征手段。

通过扫描电子显微镜(SEM)和原子力显微镜(AFM)观察石墨烯的微观形貌和厚度。

利用拉曼光谱(Raman spectroscopy)分析石墨烯的结构和层数。

石墨烯简单介绍

石墨烯简单介绍

,是室温
构造与性能
热学性能
① 单层石墨烯旳
,
比碳纳米管旳而传
导率3000-3500Wm·k还要高,相比之下,工业界中被广泛使用旳散
热 材料金属铜旳热传导率只有400Wm·k
② 伴随石墨烯层数旳增长,其热传导率逐渐下降;当石墨烯从2层增 至4层时,其热导率从2800Wmk降低至1300Wmk;当层数到达5-8 层,减小到石墨旳热导率
2004英国曼彻斯特大学Andre Geim和他旳徒弟 Konstantin Novoselov在试验室用一种非常简朴旳措 施得到越来越薄旳石墨薄片。他们从石墨中剥离 出石墨片,然后将薄片旳两面粘在一种特殊旳胶 带上,撕开胶带,就能把石墨片一分为二。不断 地这么操作,于是薄片越来越薄,最终,他们得 到了仅由一层碳原子构成旳薄片,这就是石墨烯 。所以两人共同取得2023年诺贝尔物理学奖。
石墨烯应用
替代硅生产超级计算机
石墨烯是目前已知
旳材料。石墨烯旳
这种特征尤其适合于高频电路。高频电路是当代电子工业旳领头羊,
某些电子设备,例如手机,因为工程师们正在设法将越来越多旳信息
填充在信号中,它们被要求使用越来越高旳频率,然而手机旳工作频
率越高,热量也越高,于是,高频旳提升便受到很大旳限制。因为石 墨烯旳出现,高频提升旳发展前景似乎变得无限广阔了。 这使它在
研究人员发觉,在石墨烯样品微粒开始碎裂前,它们每100纳米距 离上可承受旳最大压力居然到达了大约2.9微牛。据科学家们测算,这 一成果相当于要施加55牛顿旳压力才干使1微米长旳石墨烯断裂。假如 物理学家们能制取出厚度相当于一般食品塑料包装袋旳(厚度约100纳
米)石墨烯,那么需要施加差不多两万牛旳压力才干将其扯断。换句 话说,假如用石墨烯制成包装袋,那么它将能承受大约两吨重旳物品。

石墨烯综述

石墨烯综述

石墨烯综述概要:自2004年石墨烯横空出世,便引起全世界科学家的关注。

随着研究的一步步深入,石墨烯的各项有点更是引起世界的惊叹。

第一次成功制备出石墨烯的两位科学家安德烈·K·海姆和康斯坦丁·沃肖洛夫也在2010年夺得诺贝尔物理学奖。

本文从石墨烯的发现,结构,特性,制备及应用几个方面出发,对石墨烯做了一次比较简单,全面的综述。

关键字:石墨烯,发现,结构,特性,制备,应用一,发现及研究进展斯哥尔摩2010年10月5日电瑞典皇家科学院5日宣布,将2010年诺贝尔物理学奖授予英国曼彻斯特大学科学家安德烈·K·海姆和康斯坦丁·沃肖洛夫,以表彰他们在石墨烯材料方面的卓越研究。

2004年,英国曼彻斯特大学的安德烈·K·海姆(Andre K. Geim)等利用胶带法制备出了石墨烯。

一问世,就受到广泛关注,对石墨烯的研究也越来越深入,石墨烯独特的碳二维结构,优越的性能,广泛的应用前景更是吸引了全世界科学家的目光。

可以说自2004年石墨烯横空出世,便轰动了整个世界,引起了全世界的研究热潮。

如今已过去五年,对石墨烯的研究热度却依然不减。

在短短的五年时间内,仅在Nature 和Science 上发表的与石墨烯相关的科研论文就达40 余篇。

新闻发布会上,美联社记者问及石墨烯的应用前景,海姆回答,他无法作具体预测,但以塑料作比,推断石墨烯“有改变人们生活的潜力”。

二,石墨烯的结构石墨是三维(或立体)的层状结构,石墨晶体中层与层之间相隔340pm,距离较大,是以范德华力结合起来的,即层与层之间属于分子晶体。

但是,由于同一平面层上的碳原子间结合很强,极难破坏,所以石墨的溶点也很高,化学性质也稳定,其中一层就是石墨烯。

石墨烯是由单层碳原子组成的六方蜂巢状二维结构,即石墨烯是一种从石墨材料中剥离出的单层碳原子面材料,是碳的二维结构。

这种石墨晶体薄膜的厚度只有0.335纳米,把20万片薄膜叠加到一起,也只有一根头发丝那么厚。

《石墨烯量子点合成与表征》实验综述报告

《石墨烯量子点合成与表征》实验综述报告

《石墨烯量子点合成与表征》实验综述报告何月珍;孙健【摘要】A new comprehensive experiment - synthesis and characterization of graphene quantum dots was recommended, and its goals, principles, instruments and agents, procedures, and the issues that need to pay attention to in the experiments were studied. The experiment was basedon the focus of chemistry, material science, and biology, and covered many experimental skills that college students learned in basic chemistry experiment, such as preparation of compounds, component analysis, and characterization by instrumentals. This experiment had a easily synthetic method, all-round characterization method, modular contents, and flexible scheduling, so it can be as the comprehensive experiment course for the students in chemistry and chemical engineering major.%介绍一个综合化学实验———石墨烯量子点的制备及其表征,阐述了其实验目的、实验原理、仪器和试剂、实验步骤和注意事项。

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氧化石墨烯还原的评价标准摘要还原氧化石墨烯(RGO)是一种有趣的有潜力的能广泛应用的纳米材料。

虽然我们花了相当大的努力一直致力于开发还原方法,但它仍然需要进一步改善,如何选择一个合适的一个特定的还原方法是一个棘手的问题。

在这项研究中,还原氧化石墨烯的研究者们准备了六个典型的方法:N2H4·H2O还原,氢氧化钠还原,NaBH4还原,水浴还原 ,高温还原以及两步还原。

我们从四个方面系统的对样品包括:分散性,还原程度、缺陷修复程度和导电性能进行比较。

在比较的基础上,我们提出了一个半定量判定氧化石墨烯还原的评价标准。

这种评价标准将有助于理解氧化石墨烯还原的机理和设计更理想的还原方法。

引言单层石墨烯,因为其不寻常的电子性质和应用于各个领域的潜力,近年来吸引了巨大的研究者的关注。

目前石墨烯的制备方法,包括化学气相沉积(CVD)、微机械剥离石墨,外延生长法和液相剥离法。

前三种方法因为其获得的石墨烯的产品均一性和层数选择性原因而受到限制。

此外,这些方法的低生产率使他们不适合大规模的应用。

大部分的最有前途生产的石墨烯的路线是石墨在液相中剥离氧化然后再还原,由于它的简单性、可靠性、大规模的能力生产、相对较低的材料成本和多方面的原因适合而适合生产。

这种化学方法诱发各种缺陷和含氧官能团,如羟基和环氧导致石墨烯的电子特性退化。

与此同时,还原过程可能导致发生聚合、离子掺杂等等。

这就使得还原方法在化学剥离法发挥至关重要的作用。

到目前为止,我们花了相当大的努力一直致力于开发还原的方法。

在这里我们展示一个简单的分类:使用还原剂(对苯二酚、二甲肼、肼、硼氢化钠、含硫化合物、铝粉、维生素C、环六亚甲基四胺、乙二胺(EDA) 、聚合电解质、还原糖、蛋白质、柠檬酸钠、一氧化碳、铁、去甲肾上腺素)在不同的条件(酸/碱、热处理和其他类似微波、光催化、声化学的,激光、等离子体、细菌呼吸、溶菌酶、茶溶液)、电化学电流,两步还原等等。

这些不同的还原方法生成的石墨烯具有不同的属性。

例如,大型生产水分散石墨烯可以很容易在没有表面活性稳定剂的条件下地实现由水合肼还原氧化石墨烯。

然而,水合肼是有毒易爆,在实际使用的过程中存在困难。

水浴还原方法可以减少缺陷和氧含量的阻扰。

最近,两个或更多类型的还原方法结合以进一步提高导电率或其他性能。

例如,水合肼还原经过热处理得到的石墨烯通常显现良好的导电性。

正如我们所知, 石墨烯独特的性能与其单层的片层结构密切相关。

然而目前有些还原方法却由于范德华力的作用造成了不可逆转的团聚,给石墨烯的后续操作及应用带来了麻烦。

尽管也有不少人报道了采用超声化学、稳定剂等手段来防止石墨烯的团聚。

其他案例主要集中在选择还原剂或反应的环境而不是产品的最终属性,尤其是不关心他们是否可以使用行业。

除此之外,它还应该指出的是,氧化石墨烯溶液的还原方法并非都适合氧化石墨烯薄膜的还原。

因为基板和氧化石墨烯薄膜本身应该满足还原条件。

因此需要一个简单而又快捷的标准来对还原石墨烯的质量进行评价。

与此同时,还原机理(关注的环氧树脂的去除)仍然是模糊的和氧化石墨烯或石墨烯的详细结构仍不清楚,很难建立一个简单的和操作简便的标准用于不同教育方法。

有报道称,电气/量子阻力是用于区分作原始/外延石墨烯。

但如果测量石墨烯的电导率仍然存在还原程度和缺陷修复程度的影响的问题。

为了避免研究人员的混淆,给常见的还原方法进行一个系统比较是很有重大意义的。

在这篇文中,我们选择了六种不同的方法对氧化石墨烯进行还原,然后对可分散性,还原程度、缺陷修复程度和通过原子力显微镜(AFM)测定电导率,紫外-可见吸收光谱、x射线光电子能谱(XPS)、拉曼光谱和四探针电导率测量等几个方面进行系统的分析。

而系统比较应该有助于理解还原的机理的和进一步发展更理想的还原法。

实验部分合成和纯化氧化石墨烯是由一个修改过的Hummer方法制备的。

天然石墨(5克,50个网格,纯度99.95%,华东公司 .)与氯化钠(100克)接触30分钟。

之后,真空过滤用水冲走氯化钠。

剩下的石墨在60 C烤箱加热24小时蒸发掉所有的水。

干燥的固体与115毫升浓硫酸在一个1000毫升圆底烧瓶中混合,在室温下搅拌24小时。

接下来,0.5 g NaNO3加到混合液中溶解20分钟。

然后将烧瓶放在冰浴,并将15克KMnO4缓慢加入,且保持温度低于20 C 1.5 h。

然后把溶液放到油浴中加热到35—40 C 1 h。

然后增加度温度70 C,保持30分钟,之后, 添加15毫升的水到瓶中,这时需要增加温度至100 c .保持温度20分钟。

二十分钟后再加入15毫升的水。

30分钟后,加入200毫升的水补。

然后加入500毫升的冰水合成悬浊液;这一步可以稀释和冷却系统到50 c。

15分钟后,加入50毫升的30%过氧化氢于烧瓶中用力搅拌。

将悬浊液在室温下搅拌1小时。

悬浊液低速离心 3次(4500 rpm,15分钟)后,用5%盐酸溶液清洗2轮,然后和蒸馏水(第一步添加0.1克NH4Cl)高速离心3次(12000 rpm,60分钟)。

最后,将氧化石墨烯保存在一个自动指示的真空硅胶干燥器中1周。

还原1.水合肼还原:在玻璃瓶将氧化石墨烯溶液(25.0毫升,0.05 wt %)与25.0毫升的水,11.0μL肼溶液(80 wt %)和175.0μL氨溶液(28 wt %)混合。

然后用力摇动或搅拌几分钟,将玻璃瓶放在水浴(95 C)1 h。

2.氢氧化钠还原:氧化石墨烯悬浊液(0.5毫克/毫升,75毫升)加入1毫升氢氧化钠溶液(8M)在70 C恒温水浴里超声处理几分钟。

3.NaBH4还原:在一个特定条件下,将75毫克氧化石墨分散在75克的水中进行声波降解法。

将600毫克的硼氢化钠溶解在15克水中加到氧化石墨烯悬浊液中,然后用5wt%碳酸钠溶液调节pH值调整到9 —10。

混合物保持在80 C1 h并不断搅拌。

在还原过程中,悬浊液从暗棕色变成黑色伴随着气体产生。

4.水浴还原:将总共35毫升的0.5 mg / mL氧化石墨烯水溶液转移到一个聚四氟乙烯内衬高压釜中保持180 C加热 6 h。

5.高温还原:将干燥好的氧化石墨烯粉末放在石英舟里,并用氩气吹洗10分钟,在氩气的保护下,快速放入预先升温到900 C的管式炉中加热30s6.两步还原:将100mg干燥的氧化石墨烯溶解在蒸馏水中制成1.0 mg / mL溶液。

用5wt%碳酸钠溶液调节溶液pH值调整到9 —10,然后直接加入800mg 硼氢化钠,在80 C水浴条件下搅拌1h。

将产物通过过滤和高速离心的方式进行洗涤和浓缩,在有五氧化二磷存在下60 C真空干燥2天。

再将干燥的产物在浓硫酸中加热到到120 C,进行回流12h,冷却后用蒸馏水稀释。

再次通过过滤和高速离心的方式进行洗涤和浓缩,将样品真空干燥后,在900C氩气保护氛围的管式炉中退火15分钟GO和RGO薄膜的制备 GO和RGO薄膜是由真空过滤方法制的的。

使用了一种纤维素酯膜(直径50毫米、孔径220纳米、升河膜)。

在60 C条件下真空干燥3天,可以得到纸状的薄膜。

鉴定 AFM(原子力显微镜,Veeco公司仪器)是用来测量氧化石墨烯薄膜的尺寸和厚度的。

硅衬底用丙酮、甲醇和异丙醇清洗然后浸泡在3-氨基丙基三乙氧基硅烷的水溶液(APTES;20毫升的水12μL APTES)中15分钟。

用蒸馏水彻底清洗然后用氩气吹干,然后将衬底在氧化石墨烯溶液中浸泡在10分钟或更长时间。

在室温下测定氧化石墨烯光学吸收特征光谱(紫外-可见分光光度计 - 2501 pc,日本岛津公司,工作范围:200—900nm)。

拉曼光谱记录用Renishaw1000共焦拉曼探针的514 nm氩离子激光器检测800—3600cm范围的光谱。

XPS使用光电子能谱仪 (热电子)的阿尔基米-雷克南辐射进行测量。

GO和RGO薄膜的电导率测量采用四点探测方法(Qianfeng SB100A / 2),在薄膜的三个不同的区域重复测量,确保样品均匀性及其几何平均值。

结果与讨论任何评估标准应该公平、全面、简单、快速、可接受,促进行业的发展。

对RGO 的评估标准也不例外。

考虑RGO大规模的应用需要在溶剂分散及其单层结构有关,因此首先考虑RGO的分散稳定性。

在之前的许多文献中,氧化石墨烯可以通过超声分散的方法,分散在水和许多有机溶剂中并保持几个星期稳定而不发生明显的沉降,但目前还没有报道对通过不同的还原方法得到的RGO的分散性进行比较。

因此,我们把分散性选为RGO评估标准一个重要的参数在我们的工作中,我们选择了三种常用溶剂:水,典型的极性有机溶剂(DMF,二甲基甲酰胺)和典型非极性溶剂(四氯化碳)来对不同还原方法的RGO进行比较分析。

首先将不同还原方法得到的RGO和GO在三种不同溶剂超声分散成0.2mg.ml-1的胶体溶液,然后静置一周。

其分散结果如图1所示,对于相同条件下刚超声结束的样品,可以看到GO和不同还原方法的到的RGO都能很好的分散在极性溶剂水和DMF中,而在非极性溶剂四氯化碳中只有通过高温还原和两步还原法得到RGO才有相对较好的分散。

然而,许多的分散稳定性都是短期的在几个小时或几天后就完全沉降了。

它还表明GO在还原后发生改变。

众所周知,悬浮液的稳定性主要取决于溶剂化程度和胶体大小。

其分散稳定性的减弱则表示溶剂和RGO之间的较弱的相互作用和较低的溶剂化程度。

进一步研究分散稳定性,我们用AFM 测量GO和RGO。

图1 GO及不同还原方法得到的RGO在水、DMF、CCl4中的分散效果图(左图为刚分散的图,右图为静止一周后的图)AFM是分析在溶剂中分散的GO或RGO的剥离程度及团聚情况的一个最直接有效的方法。

我们选择对在水中分散的GO和不同还原方法得到的RGO在硅片基底上进行AFM测试。

具体样品的AFM结果如图2所示,对于在水中分散的样品,其AFM图像都是形状不规则的非均匀厚度及横向尺寸从几纳米到微米片的存在。

如图2 D,G所示,其厚度大约在1.0到3.6nm之间,表明为单层石墨烯或多层石墨烯。

一些还原方法可以生成一定层数的RGO。

图2 GO(A)及不同还原方法得到的RGO(B:N2H4;C:NaOH;D:NaBH4;E:水浴法;F:高温法;G:两步法)的AFM表征结果图H为RGO的AFM的高度图第二个评价标准是还原程度。

越来越多的研究者开始意识到还原程度对RGO性能具有一定的影响。

我们主要采用紫外可见吸收光谱和XPS是两个表征技术来评价其还原程度。

紫外可见吸收光谱可以用作进一步了解还原方法对氧化石墨烯的影响。

氧化石墨烯一般在230nm处有一个明显的特征吸收峰,这是芳环的C=C的兀一兀*过渡吸收。

图3为GO及不同还原方法得到的RGO的紫外可见吸收光谱。

相比之下,氧化石墨烯经过还原后,其最大吸收峰都发生明显的红移趋势,其中还原方法中含有高温处理过程的其最大吸收峰一般都在>270 nm,使用还剂(水合肼或硼氢化钠)的还原方法其最大吸收峰位置一般在250~270nm,通过调节pH改变环境的还原方法其红移较小,一般在240~250nm之间。

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