Atomic covalent functionalization of graphene.
Atomic covalent functionalization of graphene.
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DOI：
10.1021/ar300143e
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发表时间：
2013-01-15
影响因子：
18.3
通讯作者：
Hersam, Mark C.
中科院分区：
文献类型：
--
作者：
Johns, James E.;Hersam, Mark C.
尽管石墨烯的物理结构是一个单原子厚的二维六方晶体，由sp2键合的碳组成，但这种简单的描述掩盖了这种迷人材料所具有的无数有趣而复杂的物理特性。由于其不寻常的电子结构和最高性能，石墨烯是许多下一代技术的主要候选者，包括高频电子学，宽带光电探测器，生物和气体传感器以及透明导电涂层。尽管如此，如果研究人员能够通过化学方法调整石墨烯的电子特性，他们可以将石墨烯更常规地应用于现实世界的技术中。例如，石墨烯的共价改性以产生与硅相当的带隙（约1 eV）将使其能够用于数字电子产品，而更大的带隙将为石墨烯基光子学提供新的机会。为此，研究人员将相当大的精力集中在石墨烯的化学功能化上。由于其高的热力学稳定性和化学惰性，需要新的方法和技术来产生共价键，而不会促进不期望的副反应或对底层碳晶格的不可逆损害。在这个帐户中，我们回顾和讨论最近的理论和实验工作研究共价修饰石墨烯使用气相原子自由基。原子自由基具有足够的能量来克服与石墨烯的基面上的共价反应相关的动力学和热力学势垒，但缺乏破坏将破坏碳晶格的C-C σ键所需的能量。此外，因为它们是原子物质，所以自由基基本上降低了混淆其他共价化学的不需要的副反应的可能性。总的来说，这些基于原子自由基的方法显示出对石墨烯的均匀功能化和具有根本不同的电子和物理性质的新型二维材料的生产的希望。具体来说，我们专注于最近的研究，原子氢，氟，氧的基础平面的石墨烯。在每一个反应中，一个高能量的活化步骤启动了这个过程，打破了局部π结构并扭曲了周围的晶格。扫描隧道显微镜实验表明，基板介导的相互作用往往占主导地位时，最初的结合事件发生。然后，我们比较这些基板的影响，通常假设真空环境的理论研究的结果。随着表面覆盖率的增加，簇通常在初始变形周围形成，并且饱和最终产物的化学计量组成强烈地取决于衬底和反应物物种。除了这些化学和结构的观察，我们回顾如何共价修饰可以扩展的物理性质的范围，在二维材料中实现。
Although graphene’s physical structure is a single atom thick, two-dimensional, hexagonal crystal of sp2 bonded carbon, this simple description belies the myriad interesting and complex physical properties attributed to this fascinating material. Because of its unusual electronic structure and superlative properties, graphene serves as a leading candidate for many next generation technologies including high frequency electronics, broadband photodetectors, biological and gas sensors, and transparent conductive coatings. Despite this promise, researchers could apply graphene more routinely in real-world technologies if they could chemically adjust graphene’s electronic properties. For example, the covalent modification of graphene to create a band gap comparable to silicon (~1 eV) would enable its use in digital electronics, and larger band gaps would provide new opportunities for graphene-based photonics. Towards this end, researchers have focused considerable effort on the chemical functionalization of graphene. Due to its high thermodynamic stability and chemical inertness, new methods and techniques are required to create covalent bonds without promoting undesirable side reactions or irreversible damage to the underlying carbon lattice. In this Account, we review and discuss recent theoretical and experimental work studying covalent modifications to graphene using gas phase atomic radicals. Atomic radicals have sufficient energy to overcome the kinetic and thermodynamic barriers associated with covalent reactions on the basal plane of graphene but lack the energy required to break the C-C sigma bonds that would destroy the carbon lattice. Furthermore, because they are atomic species, radicals substantially reduce the likelihood of unwanted side reactions that confound other covalent chemistries. Overall, these methods based on atomic radicals show promise for the homogeneous functionalization of graphene and the production of new classes of two-dimensional materials with fundamentally different electronic and physical properties. Specifically, we focus on recent studies of the addition of atomic hydrogen, fluorine, and oxygen to the basal plane of graphene. In each of these reactions a high energy, activating step initiates the process, breaking the local π structure and distorting the surrounding lattice. Scanning tunneling microscopy experiments reveal that substrate mediated interactions often dominate when the initial binding event occurs. We then compare these substrate effects with the results of theoretical studies that typically assume a vacuum environment. As the surface coverage increases, clusters often form around the initial distortion, and the stoichiometric composition of the saturated end product depends strongly on both the substrate and reactant species. In addition to these chemical and structural observations, we review how covalent modification can extend the range of physical properties that are achievable in two-dimensional materials.
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影响因子：
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