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1. Introduction介绍

石墨烯是诺贝尔奖获得的二维，单层原子尺度的碳纳米材料，几十年前被预测和研究，但直到2004年才被机械分离（Novoselov等人，2004），尽管证据表明石墨烯已经生产在小但在1962年在电子显微镜中观察到之前长时间没有实现开发（Zhu et al，2010）。这种材料被认为是有希望具有各种潜在的材料应用消息令人兴奋。由sp2杂化碳原子制成的六角晶格，石墨烯作为其他碳同素异形体（如碳纳米管，石墨和富勒烯）的基本结构元素（见图1）。尽管与其他材料相比，石墨烯具有很短的历史，但由于其非凡的物理化学性质，包括高机械强度单位质量（高于钢的200倍）（Tsoukleri等人，2009），优越的载流子迁移率（弹道运输）（Chen et al。，2008），超大比表面积（Bonaccorso et al。，2015）和良好的透明度（Nair等，2008）。总共投入了24亿美元在与这种上涨的材料（Geim和Novoselov，2015）有关的研究中，导致石墨烯的年产量和总体市场价格急剧增长，2015年超过1000万美元，生物医药，电子和能源收集和储存的销售额最多。Graphene is a Nobel-winning two-dimensional,single layer,atomic-scale carbon nanomaterial that was predicted and studied decades ago but not isolated mechanically until 2004 (Novoselov et al., 2004),although evidences showed that graphene has been produced in small quantities for long timewithout being realized before being observed in electron microscopes in 1962(Zhu et al., 2010).This material has been regarded as a promising and exciting material with various potential applications.Consisting ofhexagonal lattices made of sp2-hybridized carbon atoms,grapheneserves asa basic structural element of other carbon allotropes such as carbon nanotubes, graphite and fullerene (see Figure 1).Despite its short history compared with other materials, graphene has attracted rapidly increasing attention in virtue of its extraordinary physiochemical properties, including high mechanical strength per unit mass (200 times higher than steel)(Tsoukleri et al., 2009),superior carrier mobility (ballistic transport)(Chen et al., 2008), ultra-large specific surface area (Bonaccorso et al., 2015), and good transparency (Nair et al., 2008).Indeed, a total of 2.4 billion US dollars have been invested in researches related to this rising material (Geim and Novoselov, 2015), resulting in drastically increasing annual production and overall market value of graphene, whichexceeded10 million US dollarsin 2015 with most sales in the biomedical, electronics, and energy harvesting and storage.

Figure 1. Graphene serves as the basic structural element of other carbon allotropes such as graphite, carbon nanotubes and fullerene.
This essay is arranged as follows: Section 2 summarizesphysical, electrical, mechanical, and magneticproperties of graphene, emphasizing unique characteristics of this marvelous material that make it different from conventional materials. Section 3presents an introduction of current and potential applications of graphene, mostly in biomedical, energy, electronics.In Section 4, conclusions of this essay and personal perspectives on this topic in terms of future direction and improvements needed are proposed. Overall, this essay serves as a good introduction of graphene and summary of what have been done in this field.
2. Properties
Graphene is an outstanding material characterized by extraordinary properties. In this section, the physical, electrical, mechanical and magnetic properties of graphene are emphasized.
2.1 Physical properties
The honeycomb lattice (see Figure 2), which is the basic structural unit of graphene, is composed of two equivalentsub-lattices of carbon atoms bonded togetherbyσbonds and each carbon atomowns a πorbital that contributes to a delocalized network of electrons.Owing to its atom-thick absolute two-dimensional structure, graphene exhibits a specific surface area up to 2630 m2/g, while that of conventional nanomaterials such as carbon na本论文由英语论文网提供整理，提供论文代写，英语论文代写，代写论文，代写英语论文，代写留学生论文，代写英文论文，留学生论文代写相关核心关键词搜索。