Graphene is a rapidly rising star on the horizon of materials science and condensed-matter physics. This strictly two-dimensional material exhibits exceptionally high crystal and electronic quality, and, despite its short history, has already revealed a cornucopia of new physics and potential applications, which are briefly discussed here. Whereas one can be certain of the realness of applications only when commercial products appear, graphene no longer requires any further proof of its importance in terms of fundamental physics. Owing to its unusual electronic spectrum, graphene has led to the emergence of a new paradigm of 'relativistic' condensed-matter physics, where quantum relativistic phenomena, some of which are unobservable in high-energy physics, can now be mimicked and tested in table-top experiments. More generally, graphene represents a conceptually new class of materials that are only one atom thick, and, on this basis, offers new inroads into low-dimensional physics that has never ceased to surprise and continues to provide a fertile ground for applications.

The rise of graphene

This article reviews the basic theoretical aspects of graphene, a one-atom-thick allotrope of carbon, with unusual two-dimensional Dirac-like electronic excitations. The Dirac electrons can be controlled by application of external electric and magnetic fields, or by altering sample geometry and/or topology. The Dirac electrons behave in unusual ways in tunneling, confinement, and the integer quantum Hall effect. The electronic properties of graphene stacks are discussed and vary with stacking order and number of layers. Edge (surface) states in graphene depend on the edge termination (zigzag or armchair) and affect the physical properties of nanoribbons. Different types of disorder modify the Dirac equation leading to unusual spectroscopic and transport properties. The effects of electron-electron and electron-phonon interactions in single layer and multilayer graphene are also presented.

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The electronic properties of graphene

抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1（PfPMP1）与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用，在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员，通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

疟原虫var基因转换速率变化导致抗原变异[英]／Paul H, Robert P, Christodoulou Z, et al//Proc Natl Acad Sci U S A

We measured the elastic properties and intrinsic breaking strength of free-standing monolayer graphene membranes by nanoindentation in an atomic force microscope. The force-displacement behavior is interpreted within a framework of nonlinear elastic stress-strain response, and yields second- and third-order elastic stiffnesses of 340 newtons per meter (N m(-1)) and -690 Nm(-1), respectively. The breaking strength is 42 N m(-1) and represents the intrinsic strength of a defect-free sheet. These quantities correspond to a Young's modulus of E = 1.0 terapascals, third-order elastic stiffness of D = -2.0 terapascals, and intrinsic strength of sigma(int) = 130 gigapascals for bulk graphite. These experiments establish graphene as the strongest material ever measured, and show that atomically perfect nanoscale materials can be mechanically tested to deformations well beyond the linear regime.

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Measurement of the Elastic Properties and Intrinsic Strength of Monolayer Graphene

Graphene is a wonder material with many superlatives to its name. It is the thinnest known material in the universe and the strongest ever measured. Its charge carriers exhibit giant intrinsic mobility, have zero effective mass, and can travel for micrometers without scattering at room temperature. Graphene can sustain current densities six orders of magnitude higher than that of copper, shows record thermal conductivity and stiffness, is impermeable to gases, and reconciles such conflicting qualities as brittleness and ductility. Electron transport in graphene is described by a Dirac-like equation, which allows the investigation of relativistic quantum phenomena in a benchtop experiment. This review analyzes recent trends in graphene research and applications, and attempts to identify future directions in which the field is likely to develop.

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Graphene: Status and Prospects

NMR spectroscopic studies and Pariser-Parr Pople (PPP) calculations of donor-acceptor substituted polyenes are reported. The 13 C chemical shifts were measured and compared with the results from PPP calculations. It was found that the PPP calculations predict the charge distribution in these molecules well, and that during the excitation their dipole moments change from 6D in the ground state to over 30D in the excited state. The strong charge transfer is directly due to the excitation. It occurs mostly on the polyene chain and not on the end groups

NMR and Pariser-Parr-Pople investigations of donor-acceptor substituted polyenes

Intermolecular carbon nanotube junctions were formed by coupling chemically functionalized nanotubes with molecular linkers. A T‐shape heterojunction can be formed by reacting chloride terminated nanotubes with aliphatic diamine. Electronic devices were prepared by adsorption of functionalized nanotube junctions on Si/SiO2 substrate followed by standard e‐beam lithography. The charge transport through the junction was fund to be strongly modified by the in‐plane nanotube mechanically, leading to pronounced metal‐insulator transition.

Towards Carbon Nanotube In‐plane Transistors

Nonlinear behavior in the thermopower of doped carbon nanotubes

The analytic temperature dependence of the conductivity due to the fluctuation-induced tunnelling was known till now only within the so-called parabolic barrier approximation. It is shown that this dependence is already the general one but the connection with barrier parameters contains now explicitely the influence of the image force. We combine this result with the model assumption that the barriers are built up by less doped regions within the polyacetylene fibrils where the commensurate gap still exists. Then it is possible to obtain barrier parameters from the experimental conductivity data. The results are discussed in connection with recent observations of inhomogeneous dopant distribution.

S. Roth

Papers

NMR and Pariser-Parr-Pople investigations of donor-acceptor substituted polyenes

Towards Carbon Nanotube In‐plane Transistors

Nonlinear behavior in the thermopower of doped carbon nanotubes

The General Temperature Dependence of the Fluctuation-Induced Tunnelling Current. Application to Naarmann-Polyacetylene

Chain orientation in new polyacetylene studied by electron spin resonance