石墨烯Graphene

每个碳与三个相邻碳以 σ 键相连，C–C 键长 142 pm，剩余的 p 轨道形成贯穿整个平面的离域 π 体系。在布里渊区的 K 点，导带和价带以锥形相交（狄拉克锥），电子表现为无质量的狄拉克费米子，室温载流子迁移率可超过 10⁵ cm²/(V·s)。单层石墨烯吸收约 2.3% 的可见光，几乎透明；杨氏模量约 1 TPa，本征拉伸强度约 130 GPa；导热系数约 3000–5000 W/(m·K)。

Each carbon is σ-bonded to three neighbours at 142 pm, and the remaining p orbitals form a delocalised π system across the sheet. At the K points of the Brillouin zone the conduction and valence bands meet in cones (Dirac cones), so electrons behave as massless Dirac fermions, with room-temperature mobilities above 10⁵ cm²/(V·s). A single layer absorbs about 2.3% of visible light and is almost transparent; its Young's modulus is about 1 TPa, intrinsic tensile strength about 130 GPa and thermal conductivity about 3000–5000 W/(m·K).

1947 年华莱士用紧束缚模型计算了单层石墨的能带。长期以来人们认为严格的二维晶体在热力学上不稳定。2004 年英国曼彻斯特大学的海姆和诺沃肖洛夫用胶带反复剥离高定向热解石墨，得到单层石墨烯并测量了其电学性质，二人获 2010 年诺贝尔物理学奖。2018 年曹原等发现转角 1.1° 的双层石墨烯具有超导性。

In 1947 Wallace calculated the band structure of a single graphite layer with a tight-binding model, but strictly two-dimensional crystals were long thought thermodynamically unstable. In 2004 Andre Geim and Konstantin Novoselov at the University of Manchester repeatedly peeled highly oriented pyrolytic graphite with sticky tape, isolated single-layer graphene and measured its electrical properties; they shared the 2010 Nobel Prize in Physics. In 2018 Yuan Cao and colleagues found superconductivity in bilayer graphene twisted by 1.1°.

制备方法有机械剥离、液相剥离、铜箔上化学气相沉积（可得大面积膜）、碳化硅外延生长和氧化石墨烯还原（以休默斯法氧化石墨再还原，适合大批量）。石墨烯用于导热膜、锂电池导电剂、防腐涂料、柔性透明电极、传感器和复合材料；在半导体器件中的应用受限于没有带隙。它也推动了二硫化钼、六方氮化硼等其他二维材料的研究。

Graphene is made by mechanical exfoliation, liquid-phase exfoliation, chemical vapour deposition on copper foil (for large-area films), epitaxial growth on silicon carbide and reduction of graphene oxide (made by Hummers oxidation of graphite, suited to bulk quantities). It is used in heat-spreading films, lithium-battery conductive additives, anticorrosion coatings, flexible transparent electrodes, sensors and composites; transistor use is limited by the absence of a band gap. It has also launched research into other 2D materials such as MoS₂ and hexagonal boron nitride.